ORCID Profile
0000-0002-5360-8496
Current Organisations
University of Tasmania
,
Shandong Academy of Sciences
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Crop and Pasture Improvement (Selection and Breeding) | Plant Physiology | Crop and Pasture Production | Crop and Pasture Biochemistry and Physiology | Plant biochemistry | Plant Biology | Agricultural marine biotechnology | Plant biology | Plant physiology
Barley |
Publisher: Wiley
Date: 05-07-2016
DOI: 10.1111/PPL.12447
Abstract: Three different species of Brassica, with differential salt sensitivity were used to understand physiological mechanisms of salt tolerance operating in these species and to evaluate the relative contribution of different strategies to cope with salt load. Brassica napus was the most tolerant species in terms of the overall performance, with Brassica juncea and Brassica oleracea being much more sensitive to salt stress with no obvious difference between them. While prominent reduction in net CO2 assimilation was observed in both sensitive species, physiological mechanisms beyond this reduction differed strongly. Brassica juncea plants possessed high osmotolerance and were able to maintain high transpiration rate but showed a significant reduction in leaf chlorophyll content and efficiency of leaf photochemistry. On the contrary, B. oleracea plants possessed the highest (among the three species) tissue tolerance but showed a very significant stomatal limitation of photosynthesis. Electrophysiological experiments revealed that the high tissue tolerance in B. oleracea was related to the ability of leaf mesophyll cells to maintain highly negative membrane potential in the presence of high apoplastic Na(+) . In addition to high osmotolerance, the most tolerant B. napus showed also lesser accumulation of toxic Na(+) and Cl(-) in the leaf, possessed moderate tissue tolerance and had a superior K(+) retention ability. Taken together, the results from this study indicate that the three Brassica species employ very different mechanisms to cope with salinity and, despite its overall sensitivity to salinity, B. oleracea could be recommended as a valuable 'donor' of tissue tolerance genes to confer this trait for marker-assisted breeding programs.
Publisher: Springer Science and Business Media LLC
Date: 05-2012
DOI: 10.1038/NATURE11119
Publisher: Springer Science and Business Media LLC
Date: 19-06-2017
Publisher: Frontiers Media SA
Date: 2013
Publisher: Springer Science and Business Media LLC
Date: 11-10-2017
DOI: 10.1007/S00425-016-2605-4
Abstract: We projected meta-QTL (MQTL) for drought, salinity, and waterlogging tolerance to the physical map of barley through meta-analysis. The positions of these MQTL were refined and candidate genes were identified. Drought, salinity and waterlogging are three major abiotic stresses limiting barley yield worldwide. Breeding for abiotic stress-tolerant crops has drawn increased attention, and a large number of quantitative trait loci (QTL) for drought, salinity, and waterlogging tolerance in barley have been detected. However, very few QTL have been successfully used in marker-assisted selection (MAS) in breeding. In this study, we summarized 632 QTL for drought, salinity and waterlogging tolerance in barley. Among all these QTL, only 195 major QTL were used to conduct meta-analysis to refine QTL positions for MAS. Meta-analysis was used to map the summarized major QTL for drought, salinity, and waterlogging tolerance from different mapping populations on the barley physical map. The positions of identified meta-QTL (MQTL) were used to search for candidate genes for drought, salinity, and waterlogging tolerance in barley. Both MQTL3H.4 and MQTL6H.2 control drought tolerance in barley. Fine-mapped QTL for salinity tolerance, HvNax4 and HvNax3, were validated on MQTL1H.4 and MQTL7H.2, respectively. MQTL2H.1 and MQTL5H.3 were also the target regions for improving salinity tolerance in barley. MQTL4H.4 is the main region controlling waterlogging tolerance in barley with fine-mapped QTL for aerenchyma formation under waterlogging conditions. Detected and refined MQTL and candidate genes are crucial for future successful MAS in barley breeding.
Publisher: Wiley
Date: 20-04-2021
DOI: 10.1111/PPL.13413
Abstract: Succulent halophytes can be used as convenient models for understanding the mechanistic basis of plant adaptation to salt stress. In this work, effects of salinity (0–1000 mM NaCl range) on growth, ion accumulation, and stomatal features were investigated in the succulent halophyte Sarcocornia quinqueflora . Elevated salinity levels up to 400 mM NaCl largely promoted dry matter yield, succulence, shoot surface area, and stomatal characteristics. Plant growth was optimal at 200 mM NaCl and reduced at concentrations exceeding 600 mM NaCl. Osmotic adjustment in a succulent shoot was achieved by a massive accumulation of inorganic ions, with Na + and Cl − contributing approximately 85% of its osmolality, while organic compatible solutes and K + were responsible for only approximately 15%. Shoot K + was unchanged across the entire range of salinity treatments (200–1000 mM NaCl) and positively correlated with the transpiration rate ( R = 0.98). Carbohydrates were not reduced at high salinity compared to plants at optimal conditions, implying that growth retardation at severe salt dosages was attributed to limitations in a vacuolar Na + and Cl − sequestrations capacity rather than inadequate photosynthesis and/or substrate limitation. It is concluded that the superior salt tolerance of S. quinqueflora is achieved by the effective reliance on Na + and Cl − accumulation for osmoregulation and turgor maintenance, and efficient K + homeostasis for adequate stomatal functioning over the entire salinity range. The above findings could be instrumental in developing strategies to improve salinity stress tolerance in perennial horticultural crops and optimize their water‐use efficiency.
Publisher: Oxford University Press (OUP)
Date: 28-12-2017
DOI: 10.1093/JXB/ERX429
Publisher: Oxford University Press (OUP)
Date: 19-11-2034
DOI: 10.1093/IJE/DYAB124
Publisher: Springer India
Date: 2016
Publisher: Oxford University Press (OUP)
Date: 04-05-2020
DOI: 10.1104/PP.20.00377
Publisher: Wiley
Date: 16-01-2016
DOI: 10.1111/JAC.12122
Publisher: Oxford University Press (OUP)
Date: 11-06-2018
DOI: 10.1093/JXB/ERY194
Publisher: Elsevier BV
Date: 10-2012
DOI: 10.1016/J.EXPNEUROL.2012.06.002
Abstract: The beta-amyloid (Aβ) peptide comprises the amyloid plaques that characterise Alzheimer's disease (AD), and is thought to significantly contribute towards disease pathogenesis. Oxidative stress is elevated in the AD brain, and there is substantial evidence that the interaction between Aβ and redox-active copper is a major contributing factor towards oxidative stress in AD. The major findings of this study are that redox-active Cu(II)-Aβ causes pronounced axonal pathology in long-term neuronal cultures, including axonal fragmentation and the formation of hyperphosphorylated tau-immunoreactive axonal swellings. Notably, MAP-2 expressing dendritic processes remain largely un-affected by Cu(II)-Aβ treatment. These dystrophic axonal manifestations resemble some of the characteristic neuritic pathology of the AD brain. We show that Cu(II)-Aβ directly causes formation of intra-axonal swellings via the generation of free radicals and subsequent efflux of K+ out of neurons. In summary, we report that redox-active Cu(II)-Aβ can induce substantial neurodegenerative changes in mature neurons, and may have an important role to play in the slowly progressing pathogenesis of AD.
Publisher: Wiley
Date: 04-03-2015
DOI: 10.1111/PCE.12503
Abstract: Aquatic organisms are often exposed to dramatic changes in salinity in the environment. Despite decades of research, many questions related to molecular and physiological mechanisms mediating sensing and adaptation to salinity stress remain unanswered. Here, responses of Vaucheria erythrospora, a turgor-regulating xanthophycean alga from an estuarine habitat, have been investigated. The role of ion uptake in turgor regulation was studied using a single cell pressure probe, microelectrode ion flux estimation (MIFE) technique and membrane potential (Em ) measurements. Turgor recovery was inhibited by Gd(3+) , tetraethylammonium chloride (TEA), verapamil and orthovanadate. A NaCl-induced shock rapidly depolarized the plasma membrane while an isotonic sorbitol treatment hyperpolarized it. Turgor recovery was critically dependent on the presence of Na(+) but not K(+) and Cl(-) in the incubation media. Na(+) uptake was strongly decreased by amiloride and changes in net Na(+) and H(+) fluxes were oppositely directed. This suggests active uptake of Na(+) in V. erythrospora mediated by an antiport Na(+) /H(+) system, functioning in the direction opposite to that of the SOS1 exchanger in higher plants. The alga also retains K(+) efficiently when exposed to high NaCl concentrations. Overall, this study provides insights into mechanisms enabling V. erythrospora to regulate turgor via ion movements during hyperosmotic stress.
Publisher: Oxford University Press (OUP)
Date: 21-10-2016
DOI: 10.1104/PP.16.01347
Publisher: Wiley
Date: 20-08-2018
DOI: 10.1111/PCE.13391
Abstract: Efforts to breed salt tolerant crops could benefit from investigating previously unexplored traits. One of them is a tissue succulency. In this work, we have undertaken an electrophysiological and biochemical comparison of properties of mesophyll and storage parenchyma leaf tissues of a succulent halophyte species Carpobrotus rosii ("pigface"). We show that storage parenchyma cells of C. rossii act as Na
Publisher: Wiley
Date: 09-09-2013
DOI: 10.1111/PCE.12180
Abstract: Salt sensitive (pea) and salt tolerant (barley) species were used to understand the physiological basis of differential salinity tolerance in crops. Pea plants were much more efficient in restoring otherwise depolarized membrane potential thereby effectively decreasing K(+) efflux through depolarization-activated outward rectifying potassium channels. At the same time, pea root apex was 10-fold more sensitive to physiologically relevant H2 O2 concentration and accumulated larger amounts of H2 O2 under saline conditions. This resulted in a rapid loss of cell viability in the pea root apex. Barley plants rapidly loaded Na(+) into the xylem this increase was only transient, and xylem and leaf Na(+) concentration remained at a steady level for weeks. On the contrary, pea plants restricted xylem Na(+) loading during the first few days of treatment but failed to prevent shoot Na(+) elevation in the long term. It is concluded that superior salinity tolerance of barley plants compared with pea is conferred by at least three different mechanisms: (1) efficient control of xylem Na(+) loading (2) efficient control of H2 O2 accumulation and reduced sensitivity of non-selective cation channels to H2 O2 in the root apex and (3) higher energy saving efficiency, with less ATP spent to maintain membrane potential under saline conditions.
Publisher: Wiley
Date: 29-11-2014
DOI: 10.1111/TPJ.12372
Abstract: Hydrogen peroxide is the most stable of the reactive oxygen species (ROS) and is a regulator of development, immunity and adaptation to stress. It frequently acts by elevating cytosolic free Ca(2+) ([Ca(2+) ]cyt ) as a second messenger, with activation of plasma membrane Ca(2+) -permeable influx channels as a fundamental part of this process. At the genetic level, to date only the Ca(2) (+) -permeable Stelar K(+) Outward Rectifier (SKOR) channel has been identified as being responsive to hydrogen peroxide. We show here that the ROS-regulated Ca(2+) transport protein Annexin 1 in Arabidopsis thaliana (AtANN1) is involved in regulating the root epidermal [Ca(2+) ]cyt response to stress levels of extracellular hydrogen peroxide. Peroxide-stimulated [Ca(2+) ]cyt elevation (determined using aequorin luminometry) was aberrant in roots and root epidermal protoplasts of the Atann1 knockout mutant. Similarly, peroxide-stimulated net Ca(2+) influx and K(+) efflux were aberrant in Atann1 root mature epidermis, determined using extracellular vibrating ion-selective microelectrodes. Peroxide induction of GSTU1 (Glutathione-S-Transferase1 Tau 1), which is known to be [Ca(2+) ]cyt -dependent was impaired in mutant roots, consistent with a lesion in signalling. Expression of AtANN1 in roots was suppressed by peroxide, consistent with the need to restrict further Ca(2+) influx. Differential regulation of annexin expression was evident, with AtANN2 down-regulation but up-regulation of AtANN3 and AtANN4. Overall the results point to involvement of AtANN1 in shaping the root peroxide-induced [Ca(2+) ]cyt signature and downstream signalling.
Publisher: Frontiers Media SA
Date: 20-02-2015
Publisher: Oxford University Press (OUP)
Date: 2008
DOI: 10.1093/PCP/PCM163
Abstract: Using a model plant Nicotiana benthamiana, we have demonstrated that initial calcium uptake in response to the HR (hypersensitive response)-causing pathogen Pseudomonas syringae pv syringae 61 is followed by net calcium efflux initiated at about 12 h after the bacterial challenge and sustained for at least 48 h. Our data suggest that calcium not only acts as an important second messenger in the activation of resistance responses but may also be a downstream mediator of later cell death acceleration and completion of the defense reaction. Accordingly, we propose that the existing model of HR should be amended to include a PM Ca(2+) ATP pump as an important component of the HR to pathogens in plants.
Publisher: Informa UK Limited
Date: 07-2011
Publisher: Public Library of Science (PLoS)
Date: 27-01-2016
Publisher: Oxford University Press (OUP)
Date: 19-11-2016
DOI: 10.1093/JXB/ERV493
Publisher: Springer Science and Business Media LLC
Date: 25-11-2007
DOI: 10.1007/S00232-007-9079-Z
Abstract: In this work, we tested whether L-type Ca(2+ )channels are involved in the increase of caffeine-evoked tension in frog slow muscle fibers. Simultaneous net Ca(2+) fluxes and changes in muscle tension were measured in the presence of caffeine. Isometric tension was recorded by a mechanoelectrical transducer, and net fluxes of Ca(2+) were measured noninvasively using ion-selective vibrating microelectrodes. We show that the timing of changes in net fluxes and muscle tension coincided, suggesting interdependence of the two processes. The effects of Ca(2+)channel blockers (verapamil and gadolinium) were explored using 6 mM: caffeine both significantly reduced the action of caffeine on tension and on calcium fluxes. Both caffeine-evoked Ca(2+) leak and muscle tension were reduced by 75% in the presence of 100 microM: GdCl(3), which also caused a 92% inhibition of net Ca(2+) fluxes in the steady-state condition. Application of 10 microM: verapamil to the bath led to 30% and 52% reductions in the Ca(2+)leak caused by the presence of caffeine for the peak and steady-state values of net Ca(2+) fluxes, respectively. Verapamil (10 microM): caused a 30% reduction in the maximum values of caffeine-evoked muscle tension. Gd(3+)was a more potent inhibitor than verapamil. In conclusion, L-type Ca(2+) channels appear to play the initial role of trigger in the rather complex mechanism of slow fiber contraction, the latter process being mediated by both positive Ca(2+)-induced Ca(2+ )release and negative (Ca(2+) removal from cytosol) feedback loops.
Publisher: Springer Science and Business Media LLC
Date: 13-05-2015
DOI: 10.1007/S00425-015-2316-2
Abstract: Blue light signalling pathway in broad bean leaf epidermal cells includes key membrane transporters: plasma- and endomembrane channels and pumps of H (+) , Ca (2+) and K (+) ions, and plasma membrane redox system. Blue light signalling pathway in epidermal tissue isolated from the abaxial side of fully developed Vicia faba leaves was dissected by measuring the effect of inhibitors of second messengers on net K(+), Ca(2+) and H(+) fluxes using non-invasive ion-selective microelectrodes (the MIFE system). Switching the blue light on-off caused transient changes of the ion fluxes. The effects of seven groups of inhibitors were tested in this study: CaM antagonists, ATPase inhibitors, Ca(2+) anatagonists or chelators, agents affecting IP3 formation, redox system inhibitors, inhibitors of endomembrane Ca(2+) transport systems and an inhibitor of plasma membrane Ca(2+)-permeable channels. Most of the inhibitors had a significant effect on steady-state (basal) net fluxes, as well as on the magnitude of the transient ion flux responses to blue light fluctuations. The data presented in this study suggest that redox signalling and, specifically, plasma membrane NADPH oxidase and coupled Ca(2+) and K(+) fluxes play an essential role in blue light signal transduction.
Publisher: Public Library of Science (PLoS)
Date: 28-06-2021
DOI: 10.1371/JOURNAL.PMED.1003644
Abstract: Maternal morbidity occurs several times more frequently than mortality, yet data on morbidity burden and its effect on maternal, foetal, and newborn outcomes are limited in low- and middle-income countries. We aimed to generate prospective, reliable population-based data on the burden of major direct maternal morbidities in the antenatal, intrapartum, and postnatal periods and its association with maternal, foetal, and neonatal death in South Asia and sub-Saharan Africa. This is a prospective cohort study, conducted in 9 research sites in 8 countries of South Asia and sub-Saharan Africa. We conducted population-based surveillance of women of reproductive age (15 to 49 years) to identify pregnancies. Pregnant women who gave consent were include in the study and followed up to birth and 42 days postpartum from 2012 to 2015. We used standard operating procedures, data collection tools, and training to harmonise study implementation across sites. Three home visits during pregnancy and 2 home visits after birth were conducted to collect maternal morbidity information and maternal, foetal, and newborn outcomes. We measured blood pressure and proteinuria to define hypertensive disorders of pregnancy and woman’s self-report to identify obstetric haemorrhage, pregnancy-related infection, and prolonged or obstructed labour. Enrolled women whose pregnancy lasted at least 28 weeks or those who died during pregnancy were included in the analysis. We used meta-analysis to combine site-specific estimates of burden, and regression analysis combining all data from all sites to examine associations between the maternal morbidities and adverse outcomes. Among approximately 735,000 women of reproductive age in the study population, and 133,238 pregnancies during the study period, only 1.6% refused consent. Of these, 114,927 pregnancies had morbidity data collected at least once in both antenatal and in postnatal period, and 114,050 of them were included in the analysis. Overall, 32.7% of included pregnancies had at least one major direct maternal morbidity South Asia had almost double the burden compared to sub-Saharan Africa (43.9%, 95% CI 27.8% to 60.0% in South Asia 23.7%, 95% CI 19.8% to 27.6% in sub-Saharan Africa). Antepartum haemorrhage was reported in 2.2% (95% CI 1.5% to 2.9%) pregnancies and severe postpartum in 1.7% (95% CI 1.2% to 2.2%) pregnancies. Preecl sia or ecl sia was reported in 1.4% (95% CI 0.9% to 2.0%) pregnancies, and gestational hypertension alone was reported in 7.4% (95% CI 4.6% to 10.1%) pregnancies. Prolonged or obstructed labour was reported in about 11.1% (95% CI 5.4% to 16.8%) pregnancies. Clinical features of late third trimester antepartum infection were present in 9.1% (95% CI 5.6% to 12.6%) pregnancies and those of postpartum infection in 8.6% (95% CI 4.4% to 12.8%) pregnancies. There were 187 pregnancy-related deaths per 100,000 births, 27 stillbirths per 1,000 births, and 28 neonatal deaths per 1,000 live births with variation by country and region. Direct maternal morbidities were associated with each of these outcomes. Our findings imply that health programmes in sub-Saharan Africa and South Asia must intensify their efforts to identify and treat maternal morbidities, which affected about one-third of all pregnancies and to prevent associated maternal and neonatal deaths and stillbirths. The study is not a clinical trial.
Publisher: Elsevier BV
Date: 09-2017
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/FP16263
Abstract: Plant breeders are in the need for a convenient, reproducible, reliable and rapid screening methods to be used as a proxy for drought tolerance for a large number of genotypes. Addressing this need, we compared different physiological measures of stress in six barley (Hordeum vulgare L.) genotypes subjected to different drought treatments under glasshouse conditions. Genotypes were evaluated by measuring transpiration rate, quantum yield of PSII (chlorophyll fluorescence Fv/Fm ratio), SPAD chlorophyll meter reading, dry biomass and shoot water content. The accuracy of different methods for quantifying water stress tolerance was evaluated by measuring the rates of surviving and death in plants and leaves, and newly grown leaves after rewatering. In another experiment, the same genotypes were evaluated by applying 18% (w/v) of polyethylene glycol (PEG) to germinating seeds grown in paper rolls to induce osmotic stress, using relative root and shoot lengths as a measure of tolerance. The results suggest that transpiration measurements at the recovery stage could be the most sensitive method for separating contrasting genotypes. However, the method is time-consuming and laborious for large-scale screening. Chlorophyll content, dry biomass, shoot water content and stomatal density did not correlate with plant drought tolerance. At the same time, chlorophyll fluorescence Fv/Fm ratio showed a strong correlation with drought tolerance and could be recommended as suitable proxy for screening. Measuring relative root growth rate (length) using PEG-treated paper roll-grown seedlings also seems to be a highly suitable and promising method for screening a large number of genotypes in breeding programs.
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/FP16385
Abstract: Waterlogging and salinity stresses significantly affect crop growth and global food production, and these stresses are often interrelated because waterlogging can lead to land salinisation by transporting salts to the surface. Although the physiological and molecular mechanisms of plant responses to each of these environmental constraints have been studied in detail, fewer studies have dealt with potential mechanisms underlying plant tolerance to the combined stress. This gap in knowledge is jeopardising the success of breeding programs. In the present work we studied the physiological and agronomical responses of 12 barley varieties contrasting in salinity stress tolerance to waterlogging (WL), salinity (NaCl) and combined (WL/NaCl) stresses. Stress damage symptoms were much greater in plants under combined WL/NaCl stress than those under separate stresses. The shoot biomass, chlorophyll content, maximum photochemical efficiency of PSII and shoot K+ concentration were significantly reduced under WL/NaCl conditions, whereas shoot Na+ concentration increased. Plants exposed to salinity stress showed lower damage indexes compared with WL. Chlorophyll fluorescence Fv/Fm value showed the highest correlation with the stress damage index under WL/NaCl conditions (r = –0.751) compared with other measured physiological traits, so was nominated as a good parameter to rank the tolerance of varieties. Average FW was reduced to 73 ± 2, 52 ± 1 and 23 ± 2 percent of the control under NaCl, WL and combined WL/NaCl treatments respectively. Generally, the adverse effect of WL/NaCl stress was much greater in salt-sensitive varieties than in more tolerant varieties. Na+ concentrations of the shoot under control conditions were 97 ± 10 µmol g–1 DW, and increased to 1519 ± 123, 179 ± 11 and 2733 ± 248 µmol g–1 under NaCl, WL and combined WL/NaCl stresses respectively. K+ concentrations were 1378 ± 66, 1260 ± 74, 1270 ± 79 and 411 ± 92 µmol g–1 DW under control, NaCl, WL and combined WL/NaCl stresses respectively. No significant correlation was found between the overall salinity stress tolerance and amount of Na+ accumulated in plant shoots after 15 days of exposure to 250 mM NaCl stress. However, plants exposed to combined salinity and WL stress showed a negative correlation between shoot Na+ accumulation and extent of salinity damage. Overall, the reported results indicate that K+ reduction in the plants under combined WL/NaCl stress, but not stress-induced Na+ accumulation in the shoot, was the most critical feature in determining the overall plant performance under combined stress conditions.
Publisher: Public Library of Science (PLoS)
Date: 27-04-2011
Publisher: Oxford University Press (OUP)
Date: 04-04-2005
DOI: 10.1093/JXB/ERI138
Abstract: Photosynthetic characteristics, leaf ionic content, and net fluxes of Na(+), K(+), and Cl(-) were studied in barley (Hordeum vulgare L) plants grown hydroponically at various Na/Ca ratios. Five weeks of moderate (50 mM) or high (100 mM) NaCl stress caused a significant decline in chlorophyll content, chlorophyll fluorescence characteristics, and stomatal conductance (g(s)) in plant leaves grown at low calcium level. Supplemental Ca(2+) enabled normal photochemical efficiency of PSII (F(v)/F(m) around 0.83), restored chlorophyll content to 80-90% of control, but had a much smaller (50% of control) effect on g(s). In experiments on excised leaves, not only Ca(2+), but also other alent cations (in particular, Ba(2+) and Mg(2+)), significantly ameliorated the otherwise toxic effect of NaCl on leaf photochemistry, thus attributing potential targets for such amelioration to leaf tissues. To study the underlying ionic mechanisms of this process, the MIFE technique was used to measure the kinetics of net Na(+), K(+), and Cl(-) fluxes from salinized barley leaf mesophyll in response to physiological concentrations of Ca(2+), Ba(2+), Mg(2+), and Zn(2+). Addition of 20 mM Na(+) as NaCl or Na(2)SO(4) to the bath caused significant uptake of Na(+) and efflux of K(+). These effects were reversed by adding 1 mM alent cations to the bath solution, with the relative efficiency Ba(2+)>Zn(2+)=Ca(2+)>Mg(2+). Effect of alent cations on Na(+) efflux was transient, while their application caused a prolonged shift towards K(+) uptake. This suggests that, in addition to their known ability to block non-selective cation channels (NSCC) responsible for Na(+) entry, alent cations also control the activity or gating properties of K(+) transporters at the mesophyll cell plasma membrane, thereby assisting in maintaining the high K/Na ratio required for optimal leaf photosynthesis.
Publisher: MDPI AG
Date: 29-04-2013
DOI: 10.3390/IJMS14059267
Publisher: Elsevier BV
Date: 02-2019
Publisher: Springer Science and Business Media LLC
Date: 22-07-2014
DOI: 10.1007/S00425-014-2117-Z
Abstract: Salt stress reduces the ability of mesophyll tissue to respond to light. Potassium outward rectifying channels are responsible for 84 % of Na (+) induced potassium efflux from mesophyll cells. Modulation in ion transport of broad bean (Vicia faba L.) mesophyll to light under increased apoplastic salinity stress was investigated using vibrating ion-selective microelectrodes (the MIFE technique). Increased apoplastic Na(+) significantly affected mesophyll cells ability to respond to light by modulating ion transport across their membranes. Elevated apoplastic Na(+) also induced a significant K(+) efflux from mesophyll tissue. This efflux was mediated predominately by potassium outward rectifying channels (84 %) and the remainder of the efflux was through non-selective cation channels. NaCl treatment resulted in a reduction in photosystem II efficiency in a dose- and time-dependent manner. In particular, reductions in Fv'/Fm' were linked to K(+) homeostasis in the mesophyll tissue. Increased apoplastic Na(+) concentrations induced vanadate-sensitive net H(+) efflux, presumably mediated by the plasma membrane H(+)-ATPase. It is concluded that the observed pump's activation is essential for the maintenance of membrane potential and ion homeostasis in the cytoplasm of mesophyll under salt stress.
Publisher: Oxford University Press (OUP)
Date: 02-03-2017
DOI: 10.1093/PCP/PCX026
Abstract: This study has investigated mechanisms conferring beneficial effects of exogenous application of 24-epibrassinolides (EBL) on plant growth and performance under saline conditions. Barley seedlings treated with 0.25 mg l-1 EBL showed significant improvements in root hair length, shoot length, shoot fresh weight and relative water content when grown in the presence of 150 mM NaCl in the growth medium. In addition, EBL treatment significantly decreased the Na+ content in both shoots (by approximately 50%) and roots. Electrophysiological experiments revealed that pre-treatment with EBL for 1 and 24 h suppressed or completely prevented the NaCl-induced K+ leak in the elongation zone of barley roots, but did not affect root sensitivity to oxidative stress. Further experiments using Arabidopsis loss-of-function gork1-1 (lacking functional depolarization-activated outward-rectifying K+ channels in the root epidermal cells) and akt1 (lacking inward-rectifying K+ uptake channel) mutants showed that NaCl-induced K+ loss in the elongation zone of roots was reduced by EBL pre-treatment 50- to 100-fold in wild-type Col-0 and akt1, but only 10-fold in the gork1-1 mutant. At the same time, EBL treatment shifted vanadate-sensitive H+ flux towards net efflux. Taken together, these data indicate that exogenous application of EBL effectively improves plant salinity tolerance by prevention of K+ loss via regulating depolarization-activated K+ channels.
Publisher: Elsevier BV
Date: 08-2001
DOI: 10.1016/S0167-7012(01)00270-6
Abstract: This study introduced the use of a non-invasive ion-selective microelectrode (MIFE) technique to study membrane-transport processes in bacteria. Net ion fluxes and changes in the extracellular concentrations of H+, Ca2+, K+ and NH4+ in adherent bacteria, isolated from cultures at different growth stages (exponential, late exponential, and stationary phases), were monitored. With the exception of Ca2+, a significant (P=0.05) difference was found in the magnitude of net fluxes of the ions measured from bacterial cells at different stages of the population growth curve. The magnitude of the H+ response was glucose-dependent with maximum changes occurring at the highest concentration. There was a progressive increase in H+ extrusion followed by a gradual return to zero at late stationary phase. Measurements of net ion fluxes crossing the bacterial cytoplasmic membrane, demonstrated here for the first time, may offer insight into underlying mechanisms of ion transport kinetics. Applications of the non-invasive ion-selective microelectrode technique in microbiology are discussed.
Publisher: Wiley
Date: 23-03-2021
DOI: 10.1111/PPL.13352
Abstract: Wild rice Oryza rufipogon , a progenitor of cultivated rice Oryza sativa L., possesses superior salinity tolerance and is a potential donor for breeding salinity tolerance traits in rice. However, a mechanistic basis of salinity tolerance in this donor species has not been established. Here, we examined salinity tolerance from the early vegetative stage to maturity in O. rufipogon in comparison with a salt‐susceptible (Koshihikari) and a salt‐tolerant (Reiziq) variety of O. sativa . We assessed their phylogeny and agronomical traits, photosynthetic performance, ion contents, as well as gene expression in response to salinity stress. Salt‐tolerant O. rufipogon exhibited efficient leaf photosynthesis and less damage to leaf tissues during the course of salinity treatment. In addition, O. rufipogon showed a significantly higher tissue Na + accumulation that is achieved by vacuolar sequestration compared to the salt tolerant O. sativa indica subspecies. These findings are further supported by the upregulation of genes involved with ion transport and sequestration (e.g. high affinity K + transporter 1 [ HKT1 ], Na + /H + exchanger 1 [ NHX1 ] and vacuolar H + ‐ATPase c [ VHA‐c ]) in salt‐tolerant O. rufipogon as well as by the close phylogenetic relationship of key salt‐responsive genes in O. rufipogon to these in salt‐tolerant wild rice species such as O. coarctata . Thus, the high accumulation of Na + in the leaves of O. rufipogon acts as a cheap osmoticum to minimize the high energy cost of osmolyte biosynthesis and excessive reactive oxygen species production. These mechanisms demonstrated that O. rufipogon has important traits that can be used for improving salinity tolerance in cultivated rice.
Publisher: Oxford University Press (OUP)
Date: 23-06-2016
DOI: 10.1093/JXB/ERW236
Publisher: Springer Science and Business Media LLC
Date: 05-06-2015
Publisher: Proceedings of the National Academy of Sciences
Date: 17-04-2017
Abstract: The Venus flytrap has been in the focus of scientists since Darwin’s time. Carnivorous plants, with their specialized lifestyle, including insect capture, as well as digestion and absorption of prey, developed unique tools to gain scarce nutrients. In this study, we describe mechanistic insights into the cascade of events following the capture of insect prey. Action potentials evoked by the struggling prey are translated into touch-inducible hormone signals that promote the formation of secretory vesicles. Different varieties of digestive compounds are released sequentially into the flytrap’s “green stomach” and break down the captured animal. Amperometry provides insight into the kinetics and chemistry of the stimulus-coupled glandular secretion process.
Publisher: Springer Science and Business Media LLC
Date: 2010
Publisher: Oxford University Press (OUP)
Date: 20-01-2018
DOI: 10.1093/JXB/ERY010
Publisher: Elsevier BV
Date: 09-2018
Publisher: Wiley
Date: 28-12-2013
DOI: 10.1002/CBF.2946
Abstract: Endoplasmic reticulum (ER) stress and oxidative stress have recently been linked to the pathogenesis of inflammatory bowel diseases. Under physiological conditions, intestinal epithelial cells are exposed to ER and oxidative stress affecting the cellular ionic homeostasis. However, these altered ion flux 'signatures' during these stress conditions are poorly characterized. We investigated the kinetics of K(+) , Ca(2+) and H(+) ion fluxes during ER and oxidative stress in a colonic epithelial cell line LS174T using a non-invasive microelectrode ion flux estimation technique. ER and oxidative stress were induced by cell exposure to tunicamycin (TM) and copper ascorbate (CuAsc), respectively, from 1 to 24 h. Dramatic K(+) efflux was observed following acute ER stress with peak K(+) efflux being -30·6 and -138·7 nmolm(-2) s(-1) for 10 and 50 µg ml(-1) , respectively (p < 0·01). TM-dependent Ca(2+) uptake was more prolonged with peak values of 0·85 and 2·68 nmol m(-2) s(-1) for 10 and 50 µg ml(-1) TM, respectively (p < 0·02). Ion homeostasis was also affected by the duration of ER stress. Increased duration of TM treatment from 0 to 18 h led to increases in both K(+) efflux and Ca(2+) uptake. While K(+) changes were significantly higher at each time point tested, Ca(2+) uptake was significantly higher only after prolonged treatment (18 h). CuAsc also led to an increased K(+) efflux and Ca(2+) uptake. Functional assays to investigate the effect of inhibiting K(+) efflux with tetraethylammonium resulted in increased cell viability. We conclude that ER/oxidative stress in colonic epithelial cells cause dramatic K(+) , Ca(2+) and H(+) ion flux changes, which may predispose this lineage to poor stress recovery reminiscent of that seen in inflammatory bowel diseases.
Publisher: Wiley
Date: 07-2015
DOI: 10.1111/PLB.12188
Abstract: Vast agricultural areas are affected by flooding, causing up to 80% yield reduction and resulting in multibillion dollar losses. Up to now, the focus of plant breeders was predominantly on detrimental effects of anoxia, while other (potentially equally important) traits were essentially neglected one of these is soil elemental toxicity. Excess water triggers a progressive decrease in soil redox potential, thus increasing the concentration of Mn(2+) that can be toxic to plants if above a specific threshold. This work aimed to quantify the relative contribution of Mn(2+) toxicity to waterlogging stress tolerance, using barley as a case study. Twenty barley (Hordeum vulgare) genotypes contrasting in waterlogging stress tolerance were studied for their ability to cope with toxic (1 mm) amounts of Mn(2+) in the root rhizosphere. Under Mn(2+) toxicity, chlorophyll content of most waterlogging-tolerant genotypes (TX9425, Yerong, CPI-71284-48 and CM72) remained above 60% of the control value, whereas sensitive genotypes (Franklin and Naso Nijo) had 35% less chlorophyll than 35% of controls. Manganese concentration in leaves was not related to visual Mn(2+) toxicity symptoms, suggesting that various Mn(2+) tolerance mechanisms might operate in different tolerant genotypes, i.e. avoidance versus tissue tolerance. The overall significant (r = 0.60) correlation between tolerance to Mn(2+) toxicity and waterlogging in barley suggests that plant breeding for tolerance to waterlogging traits may be advanced by targeting mechanisms conferring tolerance to Mn(2+) toxicity, at least in this species.
Publisher: Humana Press
Date: 10-2012
DOI: 10.1007/978-1-62703-152-3_11
Abstract: Noninvasive microelectrode ion flux measurements (the MIFE™ technique) allow the concurrent quantification of net fluxes of several ions with high spatial (several μm) and temporal (ca 5 s) resolution. The MIFE technique has become a popular tool for studying the adaptive responses of plant cells and tissues to a large number of abiotic and biotic stresses. This chapter briefly summarizes some key findings on spatial and temporal organization of plant nutrient acquisition obtained by the MIFE technique, as well as the MIFE contribution towards elucidating the mechanisms behind a plant's perception and signaling of major abiotic stresses. The full protocols for microelectrode fabrication, calibration, and use are then given, and two basic routines for mapping root ion flux profiles and studying transient ion flux kinetics are given.
Publisher: Springer Science and Business Media LLC
Date: 16-08-2018
Publisher: Springer Science and Business Media LLC
Date: 04-08-2005
DOI: 10.1007/S00425-005-0074-2
Abstract: The SOS signal-transduction pathway is known to be important for ion homeostasis and salt tolerance in plants. However, there is a lack of in planta electrophysiological data about how the changes in signalling and ion transport activity are integrated at the cellular and tissue level. In this study, using the non-invasive ion flux MIFE technique, we compared net K+, H+ and Na+ fluxes from elongation and mature root zones of Arabidopsis wild type Columbia and sos mutants. Our results can be summarised as follows: (1) SOS mutations affect the function of the entire root, not just the root apex (2) SOS signalling pathway is highly branched (3) Na+ effects on SOS1 may by-pass the SOS2/SOS3 complex in the root apex (4) SOS mutation affects H+ transport even in the absence of salt stress (5) SOS1 mutation affects intracellular K+ homeostasis with a plasma membrane depolarisation-activated outward-rectifying K+ channel being a likely target (6) H+ pump also may be a target of SOS signalling. We provide an improved model of SOS signalling and discuss physiological mechanisms underlying salt stress perception and signalling in plants. Our work shows that in planta studies are essential for understanding the functional genomics of plant salt tolerance.
Publisher: Elsevier BV
Date: 07-2008
DOI: 10.1016/J.RESMIC.2008.04.011
Abstract: The physiological role of cyclopropane fatty acids (CFAs) in acid stress resistance was studied by in situ microelectrode H+ flux measurements of Escherichia coli Frag1 and its isogenic CFA-deficient mutant JBM 1. After exposure to pH 4 for 16h, net H+ influx in JBM 1 was twice that of the parent strain. H+ flux stabilisation at pH 6 after acid stress took more time in the cfa- mutant. The data suggest increased proton permeability and decreased ability to extrude H+ in the absence of CFA, and they support the hypothesis that CFAs protect E. coli in acidic environments by decreasing membrane permeability to H+.
Publisher: Humana Press
Date: 2013
DOI: 10.1007/978-1-62703-441-8_7
Abstract: Changes in ion permeability and subsequently intracellular ion concentrations play a crucial role in intracellular and intercellular communication and, as such, confer a broad array of developmental and adaptive responses in plants. These changes are mediated by the activity of plasma-membrane based transport proteins many of which are controlled by cyclic nucleotides and/or other signaling molecules. The MIFE technique for noninvasive microelectrode ion flux measuring allows concurrent quantification of net fluxes of several ions with high spatial (μm range) and temporal (ca. 5 s) resolution, making it a powerful tool to study various aspects of downstream signaling events in plant cells. This chapter details basic protocols enabling the application of the MIFE technique to study regulation of root membrane transport in general and cyclic nucleotide mediated transport in particular.
Publisher: American Society for Microbiology
Date: 04-2002
DOI: 10.1128/AEM.68.4.1794-1802.2002
Abstract: Fluorescence ratio imaging microscopy and microelectrode ion flux estimation techniques were combined to study mechanisms of pH homeostasis in Listeria monocytogenes subjected to acid stress at different levels of glucose availability. This novel combination provided a unique opportunity to measure changes in H + at either side of the bacterial membrane in real time and therefore to evaluate the rate of H + flux across the bacterial plasma membrane and its contribution to bacterial pH homeostasis. Responses were assessed at external pHs (pH o ) between 3.0 and 6.0 for three levels of glucose (0, 1, and 10 mM) in the medium. Both the intracellular pH (pH i ) and net H + fluxes were affected by the glucose concentration in the medium, with the highest absolute values corresponding to the highest glucose concentration. In the presence of glucose, the pH i remained above 7.0 within a pH o range of 4 to 6 and decreased below pH o 4. Above pH o 4, H + extrusion increased correspondingly, with the maximum value at pH o 5.5, and below pH o 4, a net H + influx was observed. Without glucose in the medium, the pH i decreased, and a net H + influx was observed below pH o 5.5. A high correlation ( R = 0.75 to 0.92) between the pH i and net H + flux changes is reported, indicating that the two processes are complementary. The results obtained support other reports indicating that membrane transport processes are the main contributors to the process of pH i homeostasis in L. monocytogenes subjected to acid stress.
Publisher: Springer Science and Business Media LLC
Date: 20-05-2015
DOI: 10.1007/S00425-015-2317-1
Abstract: Leaf tissue tolerance was strongly and positively correlated with overall salt tolerance in barley, but not in wheat where the inability of sensitive varieties to exclude Na(+) is compensated by their better ability to handle Na(+) accumulated in the shoot via tissue tolerance mechanisms. A new high-throughput assay was developed to use the excised leaves to eliminate the confounding contribution of sodium exclusion mechanisms and evaluate genetic variability in salinity tissue tolerance in a large number of wheat (Triticum aestivum and Triticum turgidum ssp. durum) and barley (Hordeum vulgare) accessions. The changes in relative chlorophyll content (measured as chlorophyll content index, CCI) in excised leaves exposed to 50 mM NaCl for 48 h were found to be a reliable indicator of leaf tissue tolerance. In both wheat and barley, relative CCI correlated strongly with the overall plant salinity tolerance (evaluated in glasshouse experiments). To a large extent, this tissue tolerance was related to more efficient vacuolar Na(+) sequestration in leaf mesophyll, as revealed by fluorescent Na(+) dye imaging experiments. However, while in barley this correlation was positive, tissue tolerance in wheat correlated negatively with overall salinity tolerance. As a result, more salt-sensitive durum wheat genotypes possessed higher tissue tolerance than bread wheat plants, and this negative correlation was present within each of bread and durum wheat clusters as well. Overall, these results indicate that the lack of effective Na(+) exclusion ability in sensitive wheat varieties is compensated by their better ability to handle Na(+) accumulated in the shoot via tissue tolerance mechanisms. Implications of these findings for plant breeding for salinity tolerance are discussed.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/FP15312
Abstract: The causal relationship between salinity and oxidative stress tolerance is well established, but specific downstream targets and the role of specific antioxidant compounds in controlling cellular ionic homeostasis remains elusive. In this work, we have compared antioxidant profiles of leaves of two quinoa genotypes contrasting in their salt tolerance, with the aim of understanding the role of enzymatic and non-enzymatic antioxidants in salinity stress tolerance. Only changes in superoxide dismutase activity were correlated with plant adaptive responses to salinity. Proline accumulation played no major role in either osmotic adjustment or in the tissue tolerance mechanism. Among other non-enzymatic antioxidants, rutin levels were increased by over 25 fold in quinoa leaves. Exogenous application of rutin to glycophyte bean leaves improved tissue tolerance and reduced detrimental effects of salinity on leaf photochemistry. Electrophysiological experiments revealed that these beneficial effects were attributed to improved potassium retention and increased rate of Na+ pumping from the cell. The lack of correlation between rutin-induced changes in K+ and H+ fluxes suggest that rutin accumulation in the cytosol scavenges hydroxyl radical formed in response to salinity treatment thus preventing K+ leak via one of ROS-activated K+ efflux pathways, rather than controlling K+ flux via voltage-gated K+-permeable channels.
Publisher: Elsevier BV
Date: 07-2018
Publisher: Springer Science and Business Media LLC
Date: 23-02-2016
DOI: 10.1007/S00122-016-2693-3
Abstract: Aerenchyma formation after 7 days of waterlogging in commercial potting mixture can be a reliable, fast, and widely utilized approach for the selection of waterlogging tolerant barley genotypes. One major QTL for aerenchyma formation after 7 days of waterlogging treatment was identified and the newly developed markers explained 44 % of the phenotypic variance. This QTL can now be effectively used in barley breeding programs. Waterlogging is one of the important limiting conditions for crop yield and productivity. The main feature of waterlogged soils is oxygen deprivation, due to slow gas diffusion in water. Decreased oxygen content in waterlogged soils leads to the oxygen deficiency in plant tissues, resulting in reduced energy availability for plants. Rapidly induced aerenchyma formation is critical to maintaining adequate oxygen supply and overall waterlogging tolerance in barley. In this study, we have proved that quantifying aerenchyma formation after 7 days of waterlogging in commercial potting mixture can be a reliable, fast, and widely utilised approach for the selection of waterlogging tolerant barley genotypes, which is supported by measurements of redox potential (an indicator of anaerobic conditions). This protocol was also used to identify quantitative trait loci (QTL) in a doubled haploid population of barley from the cross between Yerong (tolerant) and Franklin (sensitive) genotypes. The QTL for aerenchyma formation and root porosity were at the same location as the waterlogging tolerance QTL. Seven new markers were developed and added onto this region on chromosome 4H. One major QTL for aerenchyma formation after 7 days waterlogging treatment explained 44.0 % of the phenotypic variance. This successful QTL for aerenchyma formation can be effectively used in the marker assisted selection to improve waterlogging tolerance in barley.
Publisher: Elsevier BV
Date: 12-2016
DOI: 10.1016/J.PLAPHY.2016.10.011
Abstract: Soil salinity remains a major threat to global food security, and the progress in crop breeding for salinity stress tolerance may be achieved only by pyramiding key traits mediating plant adaptive responses to high amounts of dissolved salts in the rhizosphere. This task may be facilitated by studying natural variation in salinity tolerance among plant species and, specifically, exploring mechanisms of salinity tolerance in halophytes. The aim of this work was to establish the causal link between mesophyll ion transport activity and plant salt tolerance in a range of evolutionary contrasting halophyte and glycophyte species. Plants were grown under saline conditions in a glasshouse, followed by assessing their growth and photosynthetic performance. In a parallel set of experiments, net K
Publisher: Springer Science and Business Media LLC
Date: 26-07-2012
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.4315/0362-028X-71.6.1169
Abstract: Variability in growth limits of Listeria monocytogenes in response to low pH (adjusted with HCl) or high salinity (NaCl) was evaluated for 127 strains in brain heart infusion broth at 25 degrees C. Over 95% of strains habituated at pH 5.0 grew subsequently at pH 4.2, while 25% were able to grow at pH 4.1. More than 85% of strains preadapted to growth at 8.5% NaCl (wt/vol) subsequently grew in the presence of 11.3% NaCl, while 25% were able to grow at 13% NaCl, and 4.7% grew in the presence of 13.9% NaCl. The results extend the generally accepted growth limits for L. monocytogenes in response to these hurdles. Two strains, one of which was relatively tolerant of both hurdles, and another that was less tolerant of both hurdles, were subjected to different sequences of lethal acid (pH 3.5) and NaCl (14%, wt/vol) stresses to determine whether survival was affected by growth limits, or by sequence of application of treatment. There was no significant difference in the inactivation kinetics of the two strains, but inactivation rates were affected by different treatments. For both strains, the inactivation rates, from fastest to slowest, resulted from: (i) lethal pH and then by lethal water activity, or lethal water activity and then by lethal pH (ii) lethal pH and water activity applied simultaneously (iii) lethal pH and (iv) lethal water activity. The results demonstrated that the sequence of lethal stress application strongly influences L. monocytogenes inactivation, and that L. monocytogenes growth limits are not good predictors of survival in inimical environments.
Publisher: American Physiological Society
Date: 12-2009
DOI: 10.1152/AJPCELL.00064.2009
Abstract: Microelectrode ion flux estimation (MIFE) and patch-cl techniques were combined for noninvasive K + flux measurements and recording of activities of the dominant K + channels in the early phases of apoptosis in Jurkat cells. Staurosporine (STS, 1 μM) evoked rapid (peaking around 15 min) transient K + efflux, which then gradually decreased. This transient K + efflux occurred concurrently with the transient increase of the K + background (K bg ) TWIK-related spinal cord K + channel-like current density, followed by a drastic decrease and concomitant membrane depolarization. The Kv1.3 current density remained almost constant. Kv1.3 activation was not altered by STS, whereas the inactivation was shifted to more positive potentials. Contribution of K bg and Kv1.3 channels to the transient and posttransient STS-induced K + efflux components, respectively, was confirmed by the effects of bupivacaine, predominantly blocking K bg current, and the Kv1.3-specific blocker margatoxin. Channel-mediated K + efflux provoked a substantial cellular shrinkage and affected the activation of caspases.
Publisher: Proceedings of the National Academy of Sciences
Date: 21-05-2015
Abstract: The Venus flytrap Dionaea muscipula has been in the focus of scientists since Darwin’s time. Carnivorous plants, with their specialized lifestyle, including insect capture, as well as digestion and absorption of prey, developed unique tools to gain scarce nutrients. In this study, we identified the molecular nature of the uptake machinery for prey-derived potassium and the posttranslational regulation. For the first time, to our knowledge, we functionally characterize DmHAK5 here—a KUP/HAK/KT family member as activated by a CBL-CIPK kinase complex. Detailed electrophysiological characterization identified DmHAK5 as a proton-driven, high-affinity potassium transporter with a weak selectivity. Working hand-in-hand with the low-affinity, high-capacity K + -channel DmKT1 activated by the same kinase, the transporters allow the Venus flytrap to take up prey-derived potassium.
Publisher: American Society for Microbiology
Date: 03-2006
DOI: 10.1128/EC.5.3.480-487.2006
Abstract: Fungi normally maintain a high internal hydrostatic pressure (turgor) of about 500 kPa. In response to hyperosmotic shock, there are immediate electrical changes: a transient depolarization (1 to 2 min) followed by a sustained hyperpolarization (5 to 10 min) prior to turgor recovery (10 to 60 min). Using ion-selective vibrating probes, we established that the transient depolarization is due to Ca 2+ influx and the sustained hyperpolarization is due to H + efflux by activation of the plasma membrane H + -ATPase. Protein synthesis is not required for H + -ATPase activation. Net K + and Cl − uptake occurs at the same time as turgor recovery. The magnitude of the ion uptake is more than sufficient to account for the osmotic gradients required for turgor to return to its original level. Two osmotic mutants, os-1 and os-2 , homologs of a two-component histidine kinase sensor and the yeast high osmotic glycerol mitogen-activated protein (MAP) kinase, respectively, have lower turgor than the wild type and do not exhibit the sustained hyperpolarization after hyperosmotic treatment. The os-1 mutant does not exhibit all of the wild-type turgor-adaptive ion fluxes (Cl − uptake increases, but net K + flux barely changes and net H + efflux declines) ( os-2 was not examined). Both os mutants are able to regulate turgor but at a lower level than the wild type. Our results demonstrate that a MAP kinase cascade regulates ion transport, activation of the H + -ATPase, and net K + and Cl − uptake during turgor regulation. Other pathways regulating turgor must also exist.
Publisher: Humana Press
Date: 2012
Publisher: Oxford University Press (OUP)
Date: 23-06-2006
Abstract: Calcium can ameliorate Na+ toxicity in plants by decreasing Na+ influx through nonselective cation channels. Here, we show that elevated external [Ca2+] also inhibits Na+-induced K+ efflux through outwardly directed, K+-permeable channels. Noninvasive ion flux measuring and patch-cl techniques were used to characterize K+ fluxes from Arabidopsis (Arabidopsis thaliana) root mature epidermis and leaf mesophyll under various Ca2+ to Na+ ratios. NaCl-induced K+ efflux was not related to the osmotic component of the salt stress, was inhibited by the K+ channel blocker TEA+, was not mediated by inwardly directed K+ channels (tested in the akt1 mutant), and resulted in a significant decrease in cytosolic K+ content. NaCl-induced K+ efflux was partially inhibited by 1 mm Ca2+ and fully prevented by 10 mm Ca2+. This ameliorative effect was at least partially attributed to a less dramatic NaCl-induced membrane depolarization under high Ca2+ conditions. Patch-cl experiments (whole-cell mode) have demonstrated that two populations of Ca2+-sensitive K+ efflux channels exist in protoplasts isolated from the mature epidermis of Arabidopsis root and leaf mesophyll cells. The instantaneously activating K+ efflux channels showed weak voltage dependence and insensitivity to external and internal Na+. Another population of K+ efflux channels was slowly activating, steeply rectifying, and highly sensitive to Na+. K+ efflux channels in roots and leaves showed different Ca2+ and Na+ sensitivities, suggesting that these organs may employ different strategies to withstand salinity. Our results suggest an additional mechanism of Ca2+ action on salt toxicity in plants: the amelioration of K+ loss from the cell by regulating (both directly and indirectly) K+ efflux channels.
Publisher: Oxford University Press (OUP)
Date: 19-10-2016
DOI: 10.1093/JXB/ERW378
Publisher: Elsevier BV
Date: 02-2016
Publisher: Springer Science and Business Media LLC
Date: 19-12-2015
Publisher: Oxford University Press (OUP)
Date: 23-06-2006
Abstract: Calcium can ameliorate Na+ toxicity in plants by decreasing Na+ influx through nonselective cation channels. Here, we show that elevated external [Ca2+] also inhibits Na+-induced K+ efflux through outwardly directed, K+-permeable channels. Noninvasive ion flux measuring and patch-cl techniques were used to characterize K+ fluxes from Arabidopsis (Arabidopsis thaliana) root mature epidermis and leaf mesophyll under various Ca2+ to Na+ ratios. NaCl-induced K+ efflux was not related to the osmotic component of the salt stress, was inhibited by the K+ channel blocker TEA+, was not mediated by inwardly directed K+ channels (tested in the akt1 mutant), and resulted in a significant decrease in cytosolic K+ content. NaCl-induced K+ efflux was partially inhibited by 1 mm Ca2+ and fully prevented by 10 mm Ca2+. This ameliorative effect was at least partially attributed to a less dramatic NaCl-induced membrane depolarization under high Ca2+ conditions. Patch-cl experiments (whole-cell mode) have demonstrated that two populations of Ca2+-sensitive K+ efflux channels exist in protoplasts isolated from the mature epidermis of Arabidopsis root and leaf mesophyll cells. The instantaneously activating K+ efflux channels showed weak voltage dependence and insensitivity to external and internal Na+. Another population of K+ efflux channels was slowly activating, steeply rectifying, and highly sensitive to Na+. K+ efflux channels in roots and leaves showed different Ca2+ and Na+ sensitivities, suggesting that these organs may employ different strategies to withstand salinity. Our results suggest an additional mechanism of Ca2+ action on salt toxicity in plants: the amelioration of K+ loss from the cell by regulating (both directly and indirectly) K+ efflux channels.
Publisher: Wiley
Date: 18-08-2014
DOI: 10.1111/PCE.12422
Publisher: Oxford University Press (OUP)
Date: 25-07-2013
Abstract: Salinity (NaCl) stress impairs plant growth and inflicts severe crop losses. In roots, increasing extracellular NaCl causes Ca2+ influx to elevate cytosolic free Ca2+ ([Ca2+]cyt) as a second messenger for adaptive signaling. Amplification of the signal involves plasma membrane reduced nicotinamide adenine dinucleotide phosphate oxidase activation, with the resultant reactive oxygen species triggering Ca2+ influx. The genetic identities of the Ca2+-permeable channels involved in generating the [Ca2+]cyt signal are unknown. Potential candidates in the model plant Arabidopsis (Arabidopsis thaliana) include annexin1 (AtANN1). Here, luminescent detection of [Ca2+]cyt showed that AtANN1 responds to high extracellular NaCl by mediating reactive oxygen species-activated Ca2+ influx across the plasma membrane of root epidermal protoplasts. Electrophysiological analysis revealed that root epidermal plasma membrane Ca2+ influx currents activated by NaCl are absent from the Atann1 loss-of-function mutant. Both adaptive signaling and salt-responsive production of secondary roots are impaired in the loss-of-function mutant, thus identifying AtANN1 as a key component of root cell adaptation to salinity.
Publisher: MDPI AG
Date: 03-2018
DOI: 10.3390/IJMS19030702
Abstract: Salinity stress-induced production of reactive oxygen species (ROS) and associated oxidative damage is one of the major factors limiting crop production in saline soils. However, the causal link between ROS production and stress tolerance is not as straightforward as one may expect, as ROS may also play an important signaling role in plant adaptive responses. In this study, the causal relationship between salinity and oxidative stress tolerance in two cereal crops—barley (Hordeum vulgare) and wheat (Triticum aestivum)—was investigated by measuring the magnitude of ROS-induced net K+ and Ca2+ fluxes from various root tissues and correlating them with overall whole-plant responses to salinity. We have found that the association between flux responses to oxidative stress and salinity stress tolerance was highly tissue specific, and was also dependent on the type of ROS applied. No correlation was found between root responses to hydroxyl radicals and the salinity tolerance. However, when oxidative stress was administered via H2O2 treatment, a significant positive correlation was found for the magnitude of ROS-induced K+ efflux and Ca2+ uptake in barley and the overall salinity stress tolerance, but only for mature zone and not the root apex. The same trends were found for wheat. These results indicate high tissue specificity of root ion fluxes response to ROS and suggest that measuring the magnitude of H2O2-induced net K+ and Ca2+ fluxes from mature root zone may be used as a tool for cell-based phenotyping in breeding programs aimed to improve salinity stress tolerance in cereals.
Publisher: Wiley
Date: 19-09-2015
DOI: 10.1111/JIPB.12238
Abstract: Plant salinity tolerance is a physiologically complex trait, with numerous mechanisms contributing to it. In this work, we show that the ability of leaf mesophyll to retain K(+) represents an important and essentially overlooked component of a salinity tolerance mechanism. The strong positive correlation between mesophyll K(+) retention ability under saline conditions (quantified by the magnitude of NaCl-induced K(+) efflux from mesophyll) and the overall salinity tolerance (relative fresh weight and/or survival or damage under salinity stress) was found while screening 46 barley (Hordeum vulgare L.) genotypes contrasting in their salinity tolerance. Genotypes with intrinsically higher leaf K(+) content under control conditions were found to possess better K(+) retention ability under salinity and, hence, overall higher tolerance. Contrary to previous reports for barley roots, K(+) retention in mesophyll was not associated with an increased H(+) -pumping in tolerant varieties but instead correlated negatively with this trait. These findings are explained by the fact that increased H(+) extrusion may be needed to charge balance the activity and provide the driving force for the high affinity HAK/KUP K(+) transporters required to restore cytosolic K(+) homeostasis in salt-sensitive genotypes.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/FP14209
Abstract: Salinity tolerance is a complex trait – both physiologically and genetically – and the issue of which mechanism or trait has bigger contribution towards the overall plant performance is still hotly discussed in the literature. In this work, a broad range of barley (Hordeum vulgare L. and Hordeum spontaneum L.) genotypes contrasting in salinity stress tolerance were used to investigate the causal link between plant stomatal characteristics, tissue ion relations, and salinity tolerance. In total, 46 genotypes (including two wild barleys) were grown under glasshouse conditions and exposed to moderate salinity stress (200mM NaCl) for 5 weeks. The overall salinity tolerance correlated positively with stomata density, leaf K+ concentration and the relative contribution of inorganic ions towards osmotic adjustment in the shoot. At the same time, no correlation between salinity tolerance and stomatal conductance or leaf Na+ content in the shoot was found. Taken together, these results indicate the importance of increasing stomata density as an adaptive tool to optimise efficiency of CO2 assimilation under moderate saline conditions, as well as benefits of the predominant use of inorganic osmolytes for osmotic adjustment in barley. Another finding of note was that wild barleys showed rather different strategies dealing with salinity, as compared with cultivated varieties.
Publisher: Oxford University Press (OUP)
Date: 17-11-2016
DOI: 10.1093/PCP/PCV175
Abstract: Aluminum (Al) is prevalent in soils, but Al toxicity is manifested only under acid conditions. It causes severe damages to the root system. Short-term waterlogging stress can occur simultaneously with Al toxicity in areas with high rainfall or an inappropriate irrigation pattern. Barley (Hordeum vulgare L.) is one of the most Al-sensitive small-grained cereals. In this work, we have investigated effects of short-term treatments with hypoxia and phenolic acid (two major constraints in waterlogged soils) on root sensitivity to low-pH and Al stresses. We showed that hypoxia-primed roots maintained higher cell viability when exposed to low-pH/Al stress, in both elongation and mature root zones, and possessed superior ability to retain K(+) in response to low-pH/Al stresses. These priming effects were not related to higher H(+)-ATPase activity and better membrane potential maintenance, and could not be explained by the increased expression levels of HvHAK1, which mediates high-affinity K(+) uptake in roots. Instead, hypoxia-conditioned roots were significantly less sensitive to H2O2 treatment, indicated by the 10-fold reduction in the magnitude of K(+) efflux changes. This suggested that roots pre-treated with hypoxia desensitized reactive oxygen species (ROS)-inducible K(+) efflux channels in root epidermis, most probably via enhanced antioxidative capacity. A possible role for Ca(2+) in stress-induced ROS signaling pathways is also discussed. Overall, our results report, for the first time, the phenomenon of cross-protection between hypoxia and low-pH/Al stresses, and causally link it to the cell's ability to maintain cytosolic K(+) homeostasis.
Publisher: Wiley
Date: 2002
DOI: 10.1046/J.0031-9317.2001.1140108.X
Abstract: Although temperature-induced changes in membrane structure and activity seem to be central to chilling stress perception, the specific details of temperature effects on plant nutrient acquisition remain obscure. In this study, we have undertaken a comparative study of low temperature effects on the activity of plasma membrane transporters of different ions in corn (Zea mays L.) leaf and root tissues by non-invasive measurements of net ion fluxes using ion-selective microelectrode (the MIFE) technique. Kinetics of net H+, Ca2+, K+, Na+, NH+4 and Cl- fluxes were measured as plant tissues recovered after short-term (3 h) chilling stress. The major findings can be summarized as follows: (1) The critical temperatures, under which the recovery of the activity of plasma membrane transporters took place, were found to be the same for all ions measured and are likely to be associated with the phase transition of membrane lipids. (2) The most pronounced was the reduction in net uptake of K+ and NH+4 (3) Chilling treatment caused a significant net influx of Cl- and Na+ in the leaf tissue. (4) For the same species, the critical temperatures for membrane-transport processes in roots were 2-2.5 degrees C lower than in leaves. Possible physiological significance of these findings is discussed.
Publisher: Wiley
Date: 11-05-2014
DOI: 10.1111/PCE.12339
Abstract: This review provides a comprehensive assessment of a previously unexplored topic: elucidating the role that plasma- and organelle-based membrane transporters play in plant-adaptive responses to flooding. We show that energy availability and metabolic shifts under hypoxia and anoxia are critical in regulating membrane-transport activity. We illustrate the high tissue and time dependence of this regulation, reveal the molecular identity of transporters involved and discuss the modes of their regulation. We show that both reduced oxygen availability and accumulation of transition metals in flooded roots result in a reduction in the cytosolic K(+) pool, ultimately determining the cell's fate and transition to programmed cell death (PCD). This process can be strongly affected by hypoxia-induced changes in the amino acid pool profile and, specifically, ϒ-amino butyric acid (GABA) accumulation. It is suggested that GABA plays an important regulatory role, allowing plants to proceed with H2 O2 signalling to activate a cascade of genes that mediate plant adaptation to flooding while at the same time, preventing the cell from entering a 'suicide program'. We conclude that progress in crop breeding for flooding tolerance can only be achieved by pyramiding the numerous physiological traits that confer efficient energy maintenance, cytosolic ion homeostasis, and reactive oxygen species (ROS) control and detoxification.
Publisher: Oxford University Press (OUP)
Date: 05-12-2006
DOI: 10.1093/JXB/ERJ022
Abstract: Although oscillations in membrane-transport activity are ubiquitous in plants, the ionic mechanisms of ultradian oscillations in plant cells remain largely unknown, despite much phenomenological data. The physiological role of such oscillations is also the subject of much speculation. Over the last decade, much experimental evidence showing oscillations in net ion fluxes across the plasma membrane of plant cells has been accumulated using the non-invasive MIFE technique. In this study, a recently proposed feedback-controlled oscillatory model was used. The model adequately describes the observed ion flux oscillations within the minute range of periods and predicts: (i) strong dependence of the period of oscillations on the rate constants for the H+ pump (ii) a substantial phase shift between oscillations in net H+ and K+ fluxes (iii) cessation of oscillations when H+ pump activity is suppressed (iv) the existence of some 'window' of external temperatures and ionic concentrations, where non-d ed oscillations are observed: outside this range, even small changes in external parameters lead to progressive d ing and aperiodic behaviour (v) frequency encoding of environmental information by oscillatory patterns and (vi) strong dependence of oscillatory characteristics on cell size. All these predictions were successfully confirmed by direct experimental observations, when net ion fluxes were measured from root and leaf tissues of various plant species, or from single cells. Because oscillatory behaviour is inherent in feedback control systems having phase shifts, it is argued from this model that suitable conditions will allow oscillations in any cell or tissue. The possible physiological role of such oscillations is discussed in the context of plant adaptive responses to salinity, temperature, osmotic, hypoxia, and pH stresses.
Publisher: Microbiology Society
Date: 06-2005
Abstract: The food spoilage yeasts Zygosaccharomyces bailii and Saccharomyces cerevisiae have been proposed to resist weak-acid preservative stress by different means Z. bailii by limiting influx of preservative combined with its catabolism, S. cerevisiae by active extrusion of the preservative weak-acid anion and H + . Measurement of H + extrusion by exponential-phase Z. bailii cells suggest that, in common with S. cerevisiae , this yeast uses a plasma membrane H + -ATPase to expel H + when challenged by weak-acid preservative (benzoic acid). Simultaneous measurement of Z. bailii net H + and K + fluxes showed that net K + influx accompanies net H + efflux during acute benzoic acid stress. Such ionic coupling is known for S. cerevisiae in short-term preservative stress. Both yeasts significantly accumulated K + on long-term exposure to benzoic acid. Analysis of S. cerevisiae K + transporter mutants revealed that loss of the high affinity K + uptake system Trk1 confers sensitivity to growth in preservative. The results suggest that cation accumulation is an important factor in adaptation to weak-acid preservatives by spoilage yeasts and that Z. bailii and S. cerevisiae share hitherto unsuspected adaptive responses at the level of plasma membrane ion transport.
Publisher: CSIRO Publishing
Date: 1998
DOI: 10.1071/PP97146
Abstract: Changes in the bioelectric activity of maize leaves caused by a single light pulse (6 s 70 mol m-2 s-1) were used to compare the effects of NaCl treatment (20–200 mM) on plant growth, Na+ accumulation in leaves, chlorophyll fluorescence and pigment composition. Bioelectric responses seemed to be the most sensitive indicator of NaCl effects. Even the weakest salt treatment (20 mM) caused a statistically significant decrease (about 40%) in the litude of the bioelectric response. The higher the NaCl concentration, the smaller was the litude. Over the full concentration range, the characteristic time of response increased from about 30 to 60 sec, indicating that the rate of bioelectric changes was slowed by increasing salinity. Other reliable characteristics were found to be the fluorescence yield and quenching coefficients. The Fv/Fm ratio was not significantly affected by NaCl treatment. Changes in growth rate, biomass or pigment composition were either insensitive, or showed a plateau over a wide range of NaCl concentrations, and were inappropriate for screening. A possible link between bioelectric and fluorescence characteristics is discussed. We conclude that leaf bioelectric activity can be used together with, or instead of, chlorophyll fluorescence measurements, to screen genotypes for salt tolerance.
Publisher: Elsevier BV
Date: 06-2008
DOI: 10.4315/0362-028X-71.6.1169
Abstract: Variability in growth limits of Listeria monocytogenes in response to low pH (adjusted with HCl) or high salinity (NaCl) was evaluated for 127 strains in brain heart infusion broth at 25 degrees C. Over 95% of strains habituated at pH 5.0 grew subsequently at pH 4.2, while 25% were able to grow at pH 4.1. More than 85% of strains preadapted to growth at 8.5% NaCl (wt/vol) subsequently grew in the presence of 11.3% NaCl, while 25% were able to grow at 13% NaCl, and 4.7% grew in the presence of 13.9% NaCl. The results extend the generally accepted growth limits for L. monocytogenes in response to these hurdles. Two strains, one of which was relatively tolerant of both hurdles, and another that was less tolerant of both hurdles, were subjected to different sequences of lethal acid (pH 3.5) and NaCl (14%, wt/vol) stresses to determine whether survival was affected by growth limits, or by sequence of application of treatment. There was no significant difference in the inactivation kinetics of the two strains, but inactivation rates were affected by different treatments. For both strains, the inactivation rates, from fastest to slowest, resulted from: (i) lethal pH and then by lethal water activity, or lethal water activity and then by lethal pH (ii) lethal pH and water activity applied simultaneously (iii) lethal pH and (iv) lethal water activity. The results demonstrated that the sequence of lethal stress application strongly influences L. monocytogenes inactivation, and that L. monocytogenes growth limits are not good predictors of survival in inimical environments.
Publisher: Public Library of Science (PLoS)
Date: 11-08-2010
Publisher: Wiley
Date: 15-03-2012
DOI: 10.1111/J.1399-3054.2012.01599.X
Abstract: Two components of salinity stress are a reduction in water availability to plants and the formation of reactive oxygen species. In this work, we have used quinoa (Chenopodium quinoa), a dicotyledonous C3 halophyte species displaying optimal growth at approximately 150 mM NaCl, to study mechanisms by which halophytes cope with the afore-mentioned components of salt stress. The relative contribution of organic and inorganic osmolytes in leaves of different physiological ages (e.g. positions on the stem) was quantified and linked with the osmoprotective function of organic osmolytes. We show that the extent of the oxidative stress (UV-B irradiation) damage to photosynthetic machinery in young leaves is much less when compared with old leaves, and attribute this difference to the difference in the size of the organic osmolyte pool (1.5-fold difference under control conditions sixfold difference in plants grown at 400 mM NaCl). Consistent with this, salt-grown plants showed higher Fv/Fm values compared with control plants after UV-B exposure. Exogenous application of physiologically relevant concentrations of glycine betaine substantially mitigated oxidative stress damage to PSII, in a dose-dependent manner. We also show that salt-grown plants showed a significant (approximately 30%) reduction in stomatal density observed in all leaves. It is concluded that accumulation of organic osmolytes plays a dual role providing, in addition to osmotic adjustment, protection of photosynthetic machinery against oxidative stress in developing leaves. It is also suggested that salinity-induced reduction in stomatal density represents a fundamental mechanism by which plants optimize water use efficiency under saline conditions.
Publisher: Springer Science and Business Media LLC
Date: 09-04-2013
DOI: 10.1007/S10126-013-9499-Y
Abstract: Marine microheterotrophs thraustochytrids are emerging as a potential source for commercial production of polyunsaturated fatty acids (PUFA) that have nutritional and pharmacological values. With prospective demand for PUFAs increasing, biotechnological companies are looking for potential increases in those valuable products. However, high levels of NaCl in the culture media required for optimal thraustochytrid growth and PUFA production poses a significant problem to the biotechnological industry due to corrosion of fermenters calling for a need to reduce the amount of NaCl in the culture media, without imposing penalties on growth and yield of cultured organisms. Earlier, as reported by Shabala et al. (Environ Microbiol 11:1835-1843, 2009), we have shown that thraustochytrids use sodium predominantly for osmotic adjustment purposes and, as such, can be grown in low-salt environment without growth penalties, providing the media osmolality is adjusted. In this study, we verify if that conclusion, made for one specific strain and osmolyte only, is applicable to the larger number of strains and organic osmotica, as well as address the issue of yield quality (e.g., PUFA production in low-saline media). Using mannitol and sucrose for osmotic adjustment of the growth media enabled us to reduce NaCl concentration down to 1 mM this is 15-100-fold lower than any method proposed so far. At the same time, the yield of essential PUFAs was increased by 15 to 20 %. Taken together, these results suggest that the proposed method can be used in industrial fermenters for commercial PUFA production.
Publisher: Wiley
Date: 13-02-2014
DOI: 10.1016/J.FEBSLET.2014.01.062
Abstract: Cyclic mononucleotides are messengers in plant stress responses. Here we show that hydrogen peroxide (H2O2) induces rapid net K(+)-efflux and Ca(2+)-influx in Arabidopsis roots. Pre-treatment with either 10μM cAMP or cGMP for 1 or 24h does significantly reduce net K(+)-leakage and Ca(2+)-influx, and in the case of the K(+)-fluxes, the cell permeant cyclic mononucleotides are more effective. We also examined the effect of 10μM of the cell permeant 8-Br-cGMP on the Arabidopsis microsomal proteome and noted a specific increase in proteins with a role in stress responses and ion transport, suggesting that cGMP is sufficient to directly and/or indirectly induce complex adaptive changes to cellular stresses induced by H2O2.
Publisher: Elsevier BV
Date: 10-2014
DOI: 10.1016/J.PLAPHY.2014.07.005
Abstract: Salinity tolerance in plants is dependent on their abilities to adjust osmotically to reduced soil water potential and to keep intracellular ROS levels under control. Both these processes are believed to rely on de novo synthesis of organic osmolytes (traditionally defined as compatible solutes). However direct in planta evidence for anti-oxidant roles of compatible solutes are scarce. In this work, we induced changes in the level of endogenous organic osmolytes by exposing plants to various levels of NaCl (salinity stress 50-300 mM range) and then studying sensitivity of leaves to oxidative (UV-B) stress. Increase in the external NaCl concentrations was accompanied by the progressive accumulation in leaf Na(+). This accumulation was much higher in old leaves compared with young ones. In old leaves, three major inorganic ions (Na(+), Cl(-) and K(+)) have made 67.7% and 70.4% of leaf osmotic potential (in wheat and barley, respectively) when exposed to 200 mM NaCl treatment, while in young leaves their contribution was only 43.9% and 46.8%, respectively. Here, organic osmolytes played a substantial role in leaf osmotic adjustment. Increased accumulation of organic osmolytes correlated strongly with activity of PSII in leaves exposed to oxidation inducing UV-B treatment in both species (R(2) = 0.50 for wheat and 0.71 for barley). We conclude that salinity-induced accumulation of organic osmolytes in barley and wheat leaves correlates with increased oxidative stress tolerance and provides the evidence for a mechanism of cross-tolerance between these two stresses.
Publisher: Oxford University Press (OUP)
Date: 27-07-2007
Publisher: Walter de Gruyter GmbH
Date: 10-2011
DOI: 10.1515/BMC.2011.032
Abstract: Plants and bacteria respond to hyperosmotic stress by an increase in intracellular osmolality, adjusting their cell turgor to altered growth conditions. This can be achieved either by increased uptake or de novo synthesis of a variety of organic osmolytes (so-called ‘compatible solutes’), or by controlling fluxes of ions across cellular membranes. The relative contributions of each of these mechanisms have been debated in literature for many years and remain unresolved. This paper summarises all the arguments and reopens a discussion on the efficiency and strategies of osmotic adjustment in plants and bacteria. We show that the bulk of osmotic adjustment in both plants and bacteria is achieved by increased accumulation of inorganic osmolytes such as K + , Na + and Cl - . This is applicable to both halophyte and glycophyte species. At the same time, de novo synthesis of compatible solutes is an energetically expensive and slow option and can be used only for the fine adjustment of the cell osmotic potential. The most likely role the organic osmolytes play in osmotic adjustment is in osmoprotection of key membrane transport proteins and reactive oxygen species (ROS) scavenging. The specific mechanisms by which compatible solutes regulate activity of ion transporters remain elusive and require more thorough investigation. It is concluded that creating transgenic species with increased levels of organic osmolytes by itself is counterproductive due to high yield penalties all these attempts should be complemented by a concurrent increase in the accumulation of inorganic ions directly used for osmotic adjustment.
Publisher: Frontiers Media SA
Date: 16-11-2017
Publisher: Elsevier BV
Date: 05-2002
DOI: 10.1016/S0168-1605(01)00740-1
Abstract: Physiological aspects of the response of Listeria monocytogenes to acidic conditions and effect of glucose availability were studied by fluorescence ratio-imaging microscopy (FRIM) as compared with traditional viable counts. Three types of experiments were conducted: (i) static with measurements of intracellular pH (pHi) at extracellular pH (pHo) values ranging from pH 3.0 to 6.0 at 0.5 pH unit intervals (ii) kinetic with monitoring of bacterial responses to changes in the pHo from the value of 6.0 to 4.0 or 3.0 (iii) survival experiments studying bacterial recovery in response to a shift to favourable conditions after a treatment at low pH. All the experiments were performed at three levels of glucose in the medium (0, 1, and 10 mM). Both survival and pHi were greatly affected by pHo and glucose availability with the highest values for CFU and pHi at highest glucose concentration and pHo values in the medium in all trials. A high correlation (R2 = 0.995) between pHi and CFU counts was observed. The pH gradient started to collapse at pHo 4 and below for trials with glucose in the medium and at pHo 5.5 and below without glucose. A recovery step was proposed after the apparently lethal treatment to assess cell viability by FRIM.
Publisher: Elsevier BV
Date: 12-2018
DOI: 10.1016/J.HAL.2018.09.004
Abstract: Harmful algal blooms (HAB) are responsible for massive mortalities of wild and aquacultured fish due to noticeable gill damage, but the precise fish-killing mechanisms remain poorly understood. A non-invasive microelectrode ion flux estimation (MIFE) technique was successfully applied to assess changes in membrane-transport processes in a model fish gill cell line exposed to harmful microplankton. Net Ca
Publisher: Wiley
Date: 2009
DOI: 10.1111/J.1462-2920.2008.01748.X
Abstract: Bacteria respond to osmotic stress by a substantial increase in the intracellular osmolality, adjusting their cell turgor for altered growth conditions. Using Escherichia coli as a model organism we demonstrate here that bacterial responses to hyperosmotic stress specifically depend on the nature of osmoticum used. We show that increasing acute hyperosmotic NaCl stress above approximately 1.0 Os kg(-1) causes a dose-dependent K(+) leak from the cell, resulting in a substantial decrease in cytosolic K(+) content and a concurrent accumulation of Na(+) in the cell. At the same time, isotonic sucrose or mannitol treatment (non-ionic osmotica) results in a gradual increase of the net K(+) uptake. Ion flux data are consistent with growth experiments showing that bacterial growth is impaired by NaCl at the concentration resulting in a switch from net K(+) uptake to efflux. Microarray experiments reveal that about 40% of upregulated genes shared no similarity in their responses to NaCl and sucrose treatment, further suggesting specificity of osmotic adjustment in E. coli to ionic and non-ionic osmotica. The observed differences are explained by the specificity of the stress-induced changes in the membrane potential of bacterial cells highlighting the importance of voltage-gated K(+) transporters for bacterial adaptation to hyperosmotic stress.
Publisher: Springer International Publishing
Date: 2015
Publisher: Wiley
Date: 11-07-2017
DOI: 10.1111/PCE.12727
Abstract: Time-dependent kinetics of xylem Na
Publisher: Elsevier BV
Date: 07-2006
DOI: 10.1016/J.IJFOODMICRO.2006.01.026
Abstract: Responses of Listeria innocua and Lactobacillus delbrueckii subsp. bulgaricus to a rapid change in extracellular pH (pHex) from pHex 6 to a range of concentrations down to pHex 3.0 were examined, using HCl and lactic acid (LA) as acidulants. A new fluorescent probe 5-(and-6)-carboxy-2', 7'-dichlorofluorescein diacetate succinimidyl ester (CDCFDA-SE) was employed that enabled reliable measurements of intracellular pH (pHi) to a minimum pHi of 4.0. Changes in pHi and H+ fluxes from immobilised bacteria were measured using fluorescence ratio imaging microscopy (FRIM) and a non-invasive ion flux measuring technique (MIFE), respectively. L. innocua maintained a relatively constant pHi of 5.5-6.1 at pHex 4 and 5 via H+ extrusion. In contrast, L. delbrueckii subsp. bulgaricus progressively lowered pHi towards pHex over the entire pHex range examined. The type of acidulant used influenced pH regulation with both pHi and H+ -fluxes being more severely affected by LA compared to HCl. Overall, our data demonstrated different adaptive strategies in these two bacteria. While L. innocua expels protons to maintain a constant pHi, L. delbrueckii subsp. bulgaricus allows proton entry after acidic treatment so that pHi follows pHex.
Publisher: Wiley
Date: 18-08-2020
DOI: 10.1111/TPJ.14935
Publisher: Wiley
Date: 15-12-2011
DOI: 10.1111/J.1365-3040.2010.02251.X
Abstract: This paper reports the phenomenon of acquired cross-tolerance to oxidative stress in plants and investigates the activity of specific Ca²+ transport systems mediating this phenomenon. Nicotiana benthamiana plants were infected with Potato virus X (PVX) and exposed to oxidative [either ultraviolet (UV-C) or H₂O₂] stress. Plant adaptive responses were assessed by the combined application of a range of electrophysiological (non-invasive microelectrode ion flux measurements), biochemical (Ca²+- and H+-ATPase activity), imaging (fluorescence lifetime imaging measurements of changes in intracellular Ca²+ concentrations), pharmacological and cytological transmission electrone microscopy techniques. Virus-infected plants had a better ability to control UV-induced elevations in cytosolic-free Ca²+ and prevent structural and functional damage of chloroplasts. Taken together, our results suggest a high degree of crosstalk between UV and pathogen-induced oxidative stresses, and highlight the crucial role of Ca²+ efflux systems in acquired resistance to oxidative stress in plants.
Publisher: Springer Science and Business Media LLC
Date: 26-04-2017
DOI: 10.1007/S00122-017-2910-8
Abstract: We report the first study on the unique allele from wild barley that can improve waterlogging tolerance in cultivated barley with a substantially higher contribution to aerenchyma formation. Waterlogging is one of the major abiotic stresses that dramatically reduce barley crop yield. Direct selection on waterlogging tolerance in the field is less effective due to its viability to environment. The most effective way of selection is to choose traits that make significant contributions to the overall tolerance and are easy to score. Aerenchyma formation under waterlogging stress is one of the most effective mechanisms to provide adequate oxygen supply and overcome stress-induced hypoxia imposed on plants. In this study, a new allele for aerenchyma formation was identified from a wild barley accession TAM407227 on chromosome 4H. Compared to that identified in cultivated barley, this allele not only produced a greater proportion of aerenchyma but made a greater contribution to the overall waterlogging tolerance. The QTL explained 76.8% of phenotypic variance in aerenchyma formation with a LOD value of 51.4. Markers co-segregating with the trait were identified and can be effectively used in marker assisted selection.
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/FP03016
Abstract: The effects of various Na / Ca ratios on root growth, development, and ion acquisition patterns were studied in hydroponic experiments with barley (Hordeum vulgare L.) plants. In total, interactions between three different levels of salinity (1, 50 and 100 mM NaCl) and three different levels of Ca2+ (0.1, 1 and 10 mM) were studied (a full factorial experiment). Growth rate and biomass accumulation were significantly lower in salinised roots. In addition to reduction in extension growth, salinity also significantly affected plant developmental processes (for ex le reduced root hair density and root thickening). Supplemental Ca2+ significantly ameliorated those detrimental effects of salinity. Non-invasive, microelectrode ion-flux (MIFE) measurements showed that the onset of salt stress caused rapid and prolonged efflux of H+, K+ and NH4+ from the root epidermis. This efflux could be significantly reversed, or completely prevented, by the presence of high Ca2+ concentration in the bath solution, even after several days of salt stress. Membrane potential measurements in root epidermal cells showed that high Ca2+ levels in the bath were able to restore (otherwise depolarised) membrane potential back to control level (–120 to –130 mV). At the same time, no significant impact of Ca2+ on net Na+ uptake in plant roots was found. Some limitations of the MIFE technique for study of Na+ uptake kinetics under saline conditions, as well as possible ionic mechanisms underlying the ameliorating Ca2+ effects on ion fluxes in roots of salt-stressed plants, are discussed.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8EN00323H
Abstract: Nanoceria ROS scavenging is a key tool for understanding and improving plant tolerance to salinity, a stress that severely limits crop yield worldwide.
Publisher: Springer Berlin Heidelberg
Date: 2012
Publisher: Oxford University Press (OUP)
Date: 07-08-2014
DOI: 10.1093/PCP/PCU105
Abstract: Understanding the intrinsic mechanisms involved in the differential salinity tolerance between bread wheat and durum wheat is essential for breeding salt-tolerant varieties to cope with the global salinity issue threatening future food supply. In the past, higher salinity tolerance in bread wheat compared with durum wheat has been attributed to its better ability to exclude Na(+) from uptake. Here we show that another mechanism, namely more superior K(+) retention ability in the leaf mesophyll, also contributes to this difference. A strong positive correlation (R(2) > 0.41, P < 0.001) was found between NaCl-induced K(+) efflux in the leaf mesophyll and overall salinity tolerance in 48 wheat varieties. However, while the above correlation was strong in bread wheat, it was statistically insignificant in durum wheat. Consistent with these findings, a significantly higher relative leaf K(+) content was found in bread wheat than in durum wheat. In contrast to root tissues, the role of voltage-gated K(+) channels in K(+) retention in the wheat mesophyll was relatively small, and non-selective cation channels played a major role in controlling intracellular K(+) homeostasis. Moreover, a significant negative correlation between NaCl-induced mesophyll H(+) flux and mesophyll K(+) retention was found, and interpreted as a compensatory mechanism employed by sensitive varieties to regain K(+) leaked into the apoplast. It is concluded that bread wheat and durum wheat show different strategies of coping with salinity, and that targeting mechanisms conferring K(+) retention in the leaf mesophyll may be a promising way to improve the overall salinity tolerance in these species.
Publisher: Oxford University Press (OUP)
Date: 05-2006
DOI: 10.1111/J.1574-6976.2006.00019.X
Abstract: The regulation of membrane-transport activity is crucial for intracellular pH homeostasis, maintenance of cell osmotic potential, nutrient acquisition, signalling, and adaptation of bacterial cells. The non-invasive microelectrode ion flux estimation (MIFE) technique is a powerful tool for kinetic studies of membrane-transport processes across cellular membranes. Since 2001, when this technique was first applied to the study of membrane-transport processes in bacterial cells (J Microbiol Methods 46, 119-129), a large amount of information has been accumulated. This review summarizes some of these findings and discusses the advantages and applicability of this technique in studying bacterial adaptive responses to adverse environmental conditions. First, various methodological aspects of the application of this novel technique in microbiology are discussed. Then, several practical ex les ('case studies') are described. The latter include changes in membrane-transport activity in response to various stresses (acidic, osmotic, and temperature stresses) as well as flux changes as a function of bacterial growth stage and nutrient availability. It is shown that non-invasive ion flux measurements may provide a significant conceptual advance in our understanding of adaptive responses in bacteria, fungi and biofilms to a variety of environmental conditions. The technique can also be used for the rapid assessment of food-processing treatments aimed at reducing bacterial contamination of food and for the development of strategies to assess the resistance of organisms to antimicrobial agents.
Publisher: Wiley
Date: 24-04-2013
DOI: 10.1111/PPL.12056
Abstract: This work investigated the importance of the ability of leaf mesophyll cells to control K(+) flux across the plasma membrane as a trait conferring tissue tolerance mechanism in plants grown under saline conditions. Four wheat (Triticum aestivum and Triticum turgidum) and four barley (Hordeum vulgare) genotypes contrasting in their salinity tolerance were grown under glasshouse conditions. Seven to 10-day-old leaves were excised, and net K(+) and H(+) fluxes were measured from either epidermal or mesophyll cells upon acute 100 mM treatment (mimicking plant failure to restrict Na(+) delivery to the shoot) using non-invasive microelectrode ion flux estimation (the MIFE) system. To enable net ion flux measurements from leaf epidermal cells, removal of epicuticular waxes was trialed with organic solvents. A series of methodological experiments was conducted to test the efficiency of different methods of wax removal, and the impact of experimental procedures on cell viability, in order to optimize the method. A strong positive correlation was found between plants' ability to retain K(+) in salt-treated leaves and their salinity tolerance, in both wheat and especially barley. The observed effects were related to the ionic but not osmotic component of salt stress. Pharmacological experiments have suggested that voltage-gated K(+) -permeable channels mediate K(+) retention in leaf mesophyll upon elevated NaCl levels in the apoplast. It is concluded that MIFE measurements of NaCl-induced K(+) fluxes from leaf mesophyll may be used as an efficient screening tool for breeding in cereals for salinity tissue tolerance.
Publisher: Informa UK Limited
Date: 04-05-2015
Publisher: Wiley
Date: 07-2009
DOI: 10.1111/J.1462-2920.2009.01908.X
Abstract: A non-invasive ion-selective microelectrode technique was used to elucidate the ionic mechanisms of osmotic adjustment in a marine protist thraustochytrid. Hypoosmotic stress caused significant efflux of Na(+), Cl(-) and K(+) from thraustochytrid cells. Model calculations showed that almost complete osmotic adjustment was achieved within the first 30 min after stress onset. Of these, sodium was the major contributor (more than half of the total osmotic adjustment), with chloride being the second major contributor. The role of K(+) in the process of osmotic adjustment was relatively small. Changes in Ca(2+) and H(+) flux were attributed to intracellular signalling. Ion flux data were confirmed by growth experiments. Thraustochytrium cells showed normal growth patterns even when grown in a sodium-free solution provided the medium osmolality was adjusted by mannitol to one of the seawater. That suggests that the requirement of sodium for thraustochytrid growth cycle is due to its role in cell osmotic adjustment rather than because of the direct Na(+) involvement in cell metabolism. Altogether, these data demonstrate the evidence for turgor regulation in thraustochytrids and suggest that these cells may be grown in the absence of sodium providing that cell turgor is adjusted by some other means.
Publisher: Informa UK Limited
Date: 30-11-2021
DOI: 10.1080/14767058.2021.2005573
Abstract: To address the disproportionate burden of preterm birth (PTB) in low- and middle-income countries, this study aimed to (1) verify the performance of the United States-validated spontaneous PTB (sPTB) predictor, comprised of the IBP4/SHBG protein ratio, in subjects from Bangladesh, Pakistan and Tanzania enrolled in the Alliance for Maternal and Newborn Health Improvement (AMANHI) biorepository study, and (2) discover biomarkers that improve performance of IBP4/SHBG in the AMANHI cohort. The performance of the IBP4/SHBG biomarker was first evaluated in a nested case control validation study, then utilized in a follow-on discovery study performed on the same s les. Levels of serum proteins were measured by targeted mass spectrometry. Differences between the AMANHI and U.S. cohorts were adjusted using body mass index (BMI) and gestational age (GA) at blood draw as covariates. Prediction of sPTB < 37 weeks and < 34 weeks was assessed by area under the receiver operator curve (AUC). In the discovery phase, an artificial intelligence method selected additional protein biomarkers complementary to IBP4/SHBG in the AMANHI cohort. The IBP4/SHBG biomarker significantly predicted sPTB < 37 weeks ( A protein biomarker pair developed in the U.S. may have broader application in erse non-U.S. populations.
Start Date: 11-2012
End Date: 12-2017
Amount: $132,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 11-2022
End Date: 11-2025
Amount: $381,889.00
Funder: Australian Research Council
View Funded ActivityStart Date: 03-2023
End Date: 03-2024
Amount: $682,749.00
Funder: Australian Research Council
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