ORCID Profile
0000-0002-0565-2951
Current Organisation
Western Sydney University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Plant Cell and Molecular Biology | Plant Biology | Plant Physiology |
Publisher: MDPI AG
Date: 10-07-2020
DOI: 10.3390/IJMS21144882
Abstract: In rice, the OsHKT1 gene has been reported to be a critical determinant of salt tolerance. This gene is harbored by the SKC1 locus, and its role was attributed to Na+ unloading from the xylem. No direct evidence, however, was provided in previous studies. Also, the reported function of SKC1 on the loading and delivery of K+ to the shoot remains to be explained. In this work, we used an electrophysiological approach to compare the kinetics of Na+ uptake by root xylem parenchyma cells using wild type (WT) and NIL(SKC1) plants. Our data showed that Na+ reabsorption was observed in WT, but not NIL(SKC1) plants, thus questioning the functional role of HKT1 as a transporter operating in the direct Na+ removal from the xylem. Instead, changes in the expression level of HKT1 altered the activity of membrane transporters involved in K+ and Ca2+ acquisition and homeostasis in the rice epidermis and stele, explaining the observed phenotype. We conclude that the role of HKT1 in plant salinity tolerance cannot be attributed to merely reducing Na+ concentration in the xylem sap but triggers a complex feedback regulation of activities of other transporters involved in the maintenance of plant ionic homeostasis and signaling under stress conditions.
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: Wiley
Date: 20-08-2020
DOI: 10.1111/PCE.13845
Publisher: Wiley
Date: 18-10-2016
DOI: 10.1111/PCE.12832
Abstract: The aquaporin AtPIP2 is an abundant plasma membrane intrinsic protein in Arabidopsis thaliana that is implicated in stomatal closure, and is highly expressed in plasma membranes of root epidermal cells. When expressed in Xenopus laevis oocytes, AtPIP2 increased water permeability and induced a non-selective cation conductance mainly associated with Na
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: Oxford University Press (OUP)
Date: 24-01-2014
DOI: 10.1093/JXB/ERT423
Abstract: Many stresses are associated with increased accumulation of reactive oxygen species (ROS) and polyamines (PAs). PAs act as ROS scavengers, but export of putrescine and/or PAs to the apoplast and their catabolization by amine oxidases gives rise to H2O2 and other ROS, including hydroxyl radicals ((•)OH). PA catabolization-based signalling in apoplast is implemented in plant development and programmed cell death and in plant responses to a variety of biotic and abiotic stresses. Central to ROS signalling is the induction of Ca(2+) influx across the plasma membrane. Different ion conductances may be activated, depending on ROS, plant species, and tissue. Both H2O2 and (•)OH can activate hyperpolarization-activated Ca(2+)-permeable channels. (•)OH is also able to activate both outward K(+) current and weakly voltage-dependent conductance (ROSIC), with a variable cation-to-anion selectivity and sensitive to a variety of cation and anion channel blockers. Unexpectedly, PAs potentiated (•)OH-induced K(+) efflux in vivo, as well as ROSIC in isolated protoplasts. This synergistic effect is restricted to the mature root zone and is more pronounced in salt-sensitive cultivars compared with salt-tolerant ones. ROS and PAs suppress the activity of some constitutively expressed K(+) and non-selective cation channels. In addition, both (•)OH and PAs activate plasma membrane Ca(2+)-ATPase and affect H(+) pumping. Overall, (•)OH and PAs may provoke a substantial remodelling of cation and anion conductance at the plasma membrane and affect Ca(2+) signalling.
Publisher: Elsevier BV
Date: 2014
Publisher: Springer Science and Business Media LLC
Date: 28-08-2015
DOI: 10.1038/NCOMMS9293
Abstract: Nature Communications 6, Article number: 7879 (2015) Published: 29 July 2015 Updated: 28 August 2015. The original version of this Article contained a typographical error in the spelling of the author Matthew Gilliham, which was incorrectly given as Matthew Gillham. This has now been corrected in both the PDF and HTML versions of the Article.
Publisher: Science Alert
Date: 15-06-2008
Publisher: Elsevier BV
Date: 11-2014
DOI: 10.1016/J.TPLANTS.2014.09.001
Abstract: Soil salinity is claiming about three hectares of arable land from conventional crop farming every minute. At the same time, the challenge of feeding 9.3 billion people by 2050 is forcing agricultural production into marginal areas, and providing sufficient food for this growing population cannot be achieved without a major breakthrough in crop breeding for salinity tolerance. In this Opinion article, we argue that the current trend of targeting Na(+) exclusion mechanisms in breeding programmes for salinity tolerance in crops needs revising. We propose that progress in this area will be achieved by learning from halophytes, naturally salt-loving plants capable of surviving in harsh saline environments, by targeting the mechanisms conferring Na(+) sequestration in external storage organs.
Publisher: Oxford University Press (OUP)
Date: 21-02-2023
Abstract: Many disease resistance genes in wheat (Triticum aestivum L.) confer strong resistance to specific pathogen races or strains, and only a small number of genes confer multipathogen resistance. The Leaf rust resistance 67 (Lr67) gene fits into the latter category as it confers partial resistance to multiple biotrophic fungal pathogens in wheat and encodes a Sugar Transport Protein 13 (STP13) family hexose-proton symporter variant. Two mutations (G144R, V387L) in the resistant variant, Lr67res, differentiate it from the susceptible Lr67sus variant. The molecular function of the Lr67res protein is not understood, and this study aimed to broaden our knowledge on this topic. Biophysical analysis of the wheat Lr67sus and Lr67res protein variants was performed using Xenopus laevis oocytes as a heterologous expression system. Oocytes injected with Lr67sus displayed properties typically associated with proton-coupled sugar transport proteins—glucose-dependent inward currents, a Km of 110 ± 10 µM glucose, and a substrate selectivity permitting the transport of pentoses and hexoses. By contrast, Lr67res induced much larger sugar-independent inward currents in oocytes, implicating an alternative function. Since Lr67res is a mutated hexose-proton symporter, the possibility of protons underlying these currents was investigated but rejected. Instead, currents in Lr67res oocytes appeared to be dominated by anions. This conclusion was supported by electrophysiology and 36Cl− uptake studies and the similarities with oocytes expressing the known chloride channel from Torpedo marmorata, TmClC-0. This study provides insights into the function of an important disease resistance gene in wheat, which can be used to determine how this gene variant underpins disease resistance in planta.
Publisher: Oxford University Press (OUP)
Date: 02-05-2017
DOI: 10.1093/JXB/ERX142
Abstract: Salt stress impacts multiple aspects of plant metabolism and physiology. For instance it inhibits photosynthesis through stomatal limitation, causes excessive accumulation of sodium and chloride in chloroplasts, and disturbs chloroplast potassium homeostasis. Most research on salt stress has focused primarily on cytosolic ion homeostasis with few studies of how salt stress affects chloroplast ion homeostasis. This review asks the question whether membrane-transport processes and ionic relations are differentially regulated between glycophyte and halophyte chloroplasts and whether this contributes to the superior salt tolerance of halophytes. The available literature indicates that halophytes can overcome stomatal limitation by switching to CO2 concentrating mechanisms and increasing the number of chloroplasts per cell under saline conditions. Furthermore, salt entry into the chloroplast stroma may be critical for grana formation and photosystem II activity in halophytes but not in glycophytes. Salt also inhibits some stromal enzymes (e.g. fructose-1,6-bisphosphatase) to a lesser extent in halophyte species. Halophytes accumulate more chloride in chloroplasts than glycophytes and appear to use sodium in functional roles. We propose the molecular identities of candidate transporters that move sodium, chloride and potassium across chloroplast membranes and discuss how their operation may regulate photochemistry and photosystem I and II activity in chloroplasts.
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/CP15284
Abstract: Magnesium (Mg) is an essential nutrient that can alleviate soilborne toxicity of many ions. This review paper critically assesses the literature on interactions and mechanisms influencing Mg alleviation of aluminium (Al) and heavy metal toxicity. Hydrated radii of Mg2+ and Al3+ are similar therefore, these two ions compete for binding to ion transporters and other important biological molecules. In monocotyledonous species such as rice and wheat, millimolar concentrations of Mg alleviate Al toxicity, mainly by decreasing Al saturation and activity at cell wall and plasma membrane binding sites. In dicotyledonous legume species such as soybean (Glycine max), rice bean (Vigna umbellata) and broad bean (Vicia faba), micromolar concentrations of Mg may enhance biosynthesis of organic ligands and thus underpin alleviation of Al toxicity. Resistance to Al may be enhanced by increased expression of the genes coding for Mg transporters, as well as by upregulation of activity of Mg-transport proteins intracellular Mg2+ activity may thus be increased under Al stress, which may increase the activity of H+-ATPases. In Vicia faba, Mg-related enhancement in the activity of plasma membrane H+-ATPase under Al stress was found to be due to post-translational modification (increased phosphorylation of the penultimate threonine as well as association with regulatory 14-3-3 proteins), resulting in increased resistance to Al stress. Magnesium can alleviate heavy metal stress by decreasing negative electrical potential and thus metal ion activities at the plasma membrane surface (physico-chemical competition), by enhancing activities of enzymes involved in biosynthesis of organic ligands, and by increasing vacuolar sequestration of heavy metals via increasing H+-pumping activity at the tonoplast. Future work should concentrate on characterising the role of intracellular Mg2+ homeostasis and Mg transporters in alleviating metal stress as well as in transcriptional, translational and post-translational regulation of H+-pumps and enzymes involved in biosynthesis and exudation of organic ligands.
Publisher: Wiley
Date: 11-07-2019
DOI: 10.1111/NPH.15864
Abstract: Agriculture is expanding into regions that are affected by salinity. This review considers the energetic costs of salinity tolerance in crop plants and provides a framework for a quantitative assessment of costs. Different sources of energy, and modifications of root system architecture that would maximize water vs ion uptake are addressed. Energy requirements for transport of salt (NaCl) to leaf vacuoles for osmotic adjustment could be small if there are no substantial leaks back across plasma membrane and tonoplast in root and leaf. The coupling ratio of the H
Publisher: Springer Berlin Heidelberg
Date: 2012
Publisher: Springer International Publishing
Date: 2015
Publisher: Wiley
Date: 28-04-2010
DOI: 10.1111/J.1399-3054.2010.01377.X
Abstract: Low-pH and Al(3+) stresses are the major causes of poor plant growth in acidic soils. However, there is still a poor understanding of plant responses to low-pH and Al(3+) toxicity. Low-pH or combined low-pH and Al(3+) stress was imposed in order to measure rhizosphere pH, ion fluxes, plasma membrane potential and intracellular H(+) concentration in distal elongation and mature zones (MZs) along the longitudinal axis of Arabidopsis thaliana roots. Low-pH stress facilitated H(+) influx into root tissues and caused cytoplasmic acidification by contrast, combined low-pH/Al(3+) treatment either decreased H(+) influx in the distal elongation zone (DEZ) or induced H(+) efflux in the MZ, leading to cytoplasmic alkalinization in both zones. Low-pH stress induced an increase in rhizosphere pH in the DEZ, whereas combined low-pH/Al(3+) stress resulted in lower rhizosphere pH in both root zones compared with the low-pH treatment alone. Low-pH stress facilitated K(+) efflux the presence of Al(3+) diminished K(+) efflux or favored K(+) influx into root tissues. In both zones, low-pH treatment induced plasma membrane (PM) depolarization, which was significantly diminished (P<or= 0.05) when combined stresses (low-pH/100 microM Al(3+)) were imposed. After 60 min of exposure, low pH caused PM depolarization, whereas low pH/100 microM Al(3+) caused PM hyperpolarization. Thus, low pH and Al(3+) toxicity differentially affect root tissues and, consequently, the rhizosphere, which might underpin the differential mechanisms of plant adaptation to these abiotic stresses.
Publisher: CRC Press
Date: 05-10-2015
DOI: 10.1201/B19246-11
Publisher: Frontiers Media SA
Date: 2011
Publisher: Oxford University Press (OUP)
Date: 22-01-2015
DOI: 10.1093/JXB/ERU528
Publisher: Oxford University Press (OUP)
Date: 06-10-2011
Abstract: Reactive oxygen species (ROS) are integral components of the plant adaptive responses to environment. Importantly, ROS affect the intracellular Ca2+ dynamics by activating a range of nonselective Ca2+-permeable channels in plasma membrane (PM). Using patch-cl and noninvasive microelectrode ion flux measuring techniques, we have characterized ionic currents and net K+ and Ca2+ fluxes induced by hydroxyl radicals (OH•) in pea (Pisum sativum) roots. OH•, but not hydrogen peroxide, activated a rapid Ca2+ efflux and a more slowly developing net Ca2+ influx concurrent with a net K+ efflux. In isolated protoplasts, OH• evoked a nonselective current, with a time course and a steady-state magnitude similar to those for a K+ efflux in intact roots. This current displayed a low ionic selectivity and was permeable to Ca2+. Active OH•-induced Ca2+ efflux in roots was suppressed by the PM Ca2+ pump inhibitors eosine yellow and erythrosine B. The cation channel blockers gadolinium, nifedipine, and verapamil and the anionic channel blockers 5-nitro-2(3-phenylpropylamino)-benzoate and niflumate inhibited OH•-induced ionic currents in root protoplasts and K+ efflux and Ca2+ influx in roots. Contrary to expectations, polyamines (PAs) did not inhibit the OH•-induced cation fluxes. The net OH•-induced Ca2+ efflux was largely prolonged in the presence of spermine, and all PAs tested (spermine, spermidine, and putrescine) accelerated and augmented the OH•-induced net K+ efflux from roots. The latter effect was also observed in patch-cl experiments on root protoplasts. We conclude that PAs interact with ROS to alter intracellular Ca2+ homeostasis by modulating both Ca2+ influx and efflux transport systems at the root cell PM.
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: Frontiers Media SA
Date: 20-02-2015
Publisher: Science Alert
Date: 15-09-2005
Publisher: Oxford University Press (OUP)
Date: 24-12-2014
DOI: 10.1093/JXB/ERT430
Abstract: Halophytes are defined as plants that are adapted to live in soils containing high concentrations of salt and benefiting from it, and thus represent an ideal model to understand complex physiological and genetic mechanisms of salinity stress tolerance. It is also known that oxidative stress signalling and reactive oxygen species (ROS) detoxification are both essential components of salinity stress tolerance mechanisms. This paper comprehensively reviews the differences in ROS homeostasis between halophytes and glycophytes in an attempt to answer the questions of whether stress-induced ROS production is similar between halophytes and glycophytes is the superior salinity tolerance in halophytes attributed to higher antioxidant activity and is there something special about the specific 'pool' of enzymatic and non-enzymatic antioxidants in halophytes. We argue that truly salt-tolerant species possessing efficient mechanisms for Na(+) exclusion from the cytosol may not require a high level of antioxidant activity, as they simply do not allow excessive ROS production in the first instance. We also suggest that H2O2 'signatures' may operate in plant signalling networks, in addition to well-known cytosolic calcium 'signatures'. According to the suggested concept, the intrinsically higher superoxide dismutase (SOD) levels in halophytes are required for rapid induction of the H2O2 'signature', and to trigger a cascade of adaptive responses (both genetic and physiological), while the role of other enzymatic antioxidants may be in decreasing the basal levels of H2O2, once the signalling has been processed. Finally, we emphasize the importance of non-enzymatic antioxidants as the only effective means to prevent detrimental effects of hydroxyl radicals on cellular structures.
Publisher: Oxford University Press (OUP)
Date: 2013
DOI: 10.1093/JXB/ERS343
Publisher: Wiley
Date: 29-11-2019
DOI: 10.1111/NPH.15555
Publisher: Springer Science and Business Media LLC
Date: 19-07-2020
Publisher: Science Alert
Date: 15-03-2007
Publisher: CRC Press
Date: 22-09-2015
DOI: 10.1201/B19246-4
Publisher: Wiley
Date: 08-12-2020
DOI: 10.1111/PCE.13947
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.PLANTSCI.2015.10.003
Abstract: Soil salinity is a major environmental constraint to crop production. While the molecular identity and functional expression of Na(+) transport systems mediating Na(+) exclusion from the cytosol has been studied in detail, far less is known about the mechanisms by which plants sense high Na(+) levels in the soil and the rapid signalling events that optimise plant performance under saline conditions. This review aims to fill this gap. We first discuss the nature of putative salt stress sensors, candidates which include Na(+) transport systems, mechanosensory proteins, proteins with regulatory Na(+) binding sites, sensing mediated by cyclic nucleotide-gated channels, purine receptors, annexin and voltage gating. We suggest that several transport proteins may be clustered together to form a microdomain in a lipid raft, allowing rapid changes in the activity of an in idual protein to be translated into stress-induced Ca(2+) and H2O2 signatures. The pathways of stress signalling to downstream targets are discussed, and the kinetics and specificity of salt stress signalling between glycophytes and halophytes is compared. We argue that these sensing mechanisms operate in parallel, providing plants with a robust system for decoding information about the specific nature and severity of the imposed salt stress.
Publisher: Oxford University Press (OUP)
Date: 27-01-2011
DOI: 10.1093/JXB/ERQ456
Abstract: Magnesium is pivotal for activating a large number of enzymes hence, magnesium plays an important role in numerous physiological and biochemical processes affecting plant growth and development. Magnesium can also ameliorate aluminium phytotoxicity, but literature reports on the dynamics of magnesium homeostasis upon exposure to aluminium are rare. Herein existing knowledge on the magnesium transport mechanisms and homeostasis maintenance in plant cells is critically reviewed. Even though overexpression of magnesium transporters can alleviate aluminium toxicity in plants, the mechanisms governing such alleviation remain obscure. Possible magnesium-dependent mechanisms include (i) better carbon partitioning from shoots to roots (ii) increased synthesis and exudation of organic acid anions (iii) enhanced acid phosphatase activity (iv) maintenance of proton-ATPase activity and cytoplasmic pH regulation (v) protection against an aluminium-induced cytosolic calcium increase and (vi) protection against reactive oxygen species. Future research should concentrate on assessing aluminium toxicity and tolerance in plants with overexpressed or antisense magnesium transporters to increase understanding of the aluminium-magnesium interaction.
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: 10-04-2014
DOI: 10.1093/JXB/ERU133
Abstract: Polyamines regulate a variety of cation and K(+) channels, but their potential effects on cation-transporting ATPases are underexplored. In this work, noninvasive microelectrode ion flux estimation and conventional microelectrode techniques were applied to study the effects of polyamines on Ca(2+) and H(+) transport and membrane potential in pea roots. Externally applied spermine or putrescine (1mM) equally activated eosin yellow (EY)-sensitive Ca(2+) pumping across the root epidermis and caused net H(+) influx or efflux. Proton influx induced by spermine was suppressed by EY, supporting the mechanism in which Ca(2+) pump imports 2 H(+) per each exported Ca(2+). Suppression of the Ca(2+) pump by EY diminished putrescine-induced net H(+) efflux instead of increasing it. Thus, activities of Ca(2+) and H(+) pumps were coupled, likely due to the H(+)-pump inhibition by intracellular Ca(2+). Additionally, spermine but not putrescine caused a direct inhibition of H(+) pumping in isolated plasma membrane vesicles. Spermine, spermidine, and putrescine (1mM) induced membrane depolarization by 70, 50, and 35 mV, respectively. Spermine-induced depolarization was abolished by cation transport blocker Gd(3+), was insensitive to anion channels' blocker niflumate, and was dependent on external Ca(2+). Further analysis showed that uptake of polyamines but not polyamine-induced cationic (K(+)+Ca(2+)+H(+)) fluxes were a main cause of membrane depolarization. Polyamine increase is a common component of plant stress responses. Activation of Ca(2+) efflux by polyamines and contrasting effects of polyamines on net H(+) fluxes and membrane potential can contribute to Ca(2+) signalling and modulate a variety of transport processes across the plasma membrane under stress.
Publisher: Oxford University Press (OUP)
Date: 11-04-2013
DOI: 10.1093/JXB/ERT085
Publisher: Oxford University Press (OUP)
Date: 23-06-2016
DOI: 10.1093/JXB/ERW236
Publisher: Oxford University Press (OUP)
Date: 27-10-2016
DOI: 10.1093/JXB/ERV465
Abstract: Abiotic stresses such as salinity, drought, and flooding severely limit food and fibre production and result in penalties of in excess of US$100 billion per annum to the agricultural sector. Improved abiotic stress tolerance to these environmental constraints via traditional or molecular breeding practices requires a good understanding of the physiological and molecular mechanisms behind roots sensing of hostile soils, as well as downstream signalling cascades to effectors mediating plant adaptive responses to the environment. In this review, we discuss some common mechanisms conferring plant tolerance to these three major abiotic stresses. Central to our discussion are: (i) the essentiality of membrane potential maintenance and ATP production/availability and its use for metabolic versus adaptive responses (ii) reactive oxygen species and Ca(2+) 'signatures' mediating stress signalling and (iii) cytosolic K(+) as the common denominator of plant adaptive responses. We discuss in detail how key plasma membrane and tonoplast transporters are regulated by various signalling molecules and processes observed in plants under stress conditions (e.g. changes in membrane potential cytosolic pH and Ca(2+) reactive oxygen species polyamines abscisic acid) and how these stress-induced changes are related to expression and activity of specific ion transporters. The reported results are then discussed in the context of strategies for breeding crops with improved abiotic stress tolerance. We also discuss a classical trade-off between tolerance and yield, and possible avenues for resolving this dilemma.
Publisher: Cold Spring Harbor Laboratory
Date: 07-01-2020
DOI: 10.1101/2020.01.06.896456
Abstract: Soybean ( Glycine max ) yields are threatened by multiple stresses including soil salinity. GmSALT3 confers net shoot exclusion for both Na+ and Cl − and improves salt tolerance of soybean however, how the ER-localised GmSALT3 achieves this is unknown. Here, GmSALT3’s function was investigated in heterologous systems and near-isogenic lines that contained the full-length GmSALT3 (NIL-T salt-tolerant) or a truncated transcript Gmsalt3 (NIL-S salt-sensitive). GmSALT3 restored growth of K+-uptake-defective E. coli and contributed toward net influx and accumulation of Na+, K+, and Cl − in Xenopus laevis oocytes, while Gmsalt3 was non-functional. A time-course analysis of the NILs confirmed that shoot Cl − exclusion breaks down prior to Na+ exclusion, while grafting showed that shoot Na + exclusion occurs via a root xylem-based mechanism. In contrast, NIL-T plants exhibited significantly greater Cl − content in both the stem xylem and phloem sap compared to NIL-S, indicating that shoot Cl − exclusion likely depends upon novel phloem-based Cl − recirculation. NIL-T shoots grafted on NIL-S roots contained low shoot Cl − , which confirmed that Cl − recirculation is dependent on the presence of GmSALT3 in shoots. Overall, these findings provide new insights on GmSALT3’s impact on salinity tolerance and reveal a novel mechanism for shoot Cl– exclusion in plants. GmSALT3 improves soybean salt tolerance. Here, using heterologous expression, we found GmSALT3 is a functional ion transporter, and, in planta that it confers shoot salt exclusion through root-based Na + xylem exclusion and shoot-based Cl − exclusion via phloem derived Cl - recirculation.
Publisher: MDPI AG
Date: 18-03-2018
DOI: 10.3390/IJMS19030897
Publisher: Oxford University Press (OUP)
Date: 24-04-2013
DOI: 10.1093/PCP/PCT064
Abstract: Low-pH stress and Al(3+) toxicity affect root growth in acid soils. It was hypothesized that the capacity of genotypes to maintain Mg(2+) uptake in acidic environments may contribute to low-pH and Al resistance, but explicit evidence is lacking. In this work, an Al-resistant alr104 mutant and two Al-sensitive mutants (als5 and als3) of Arabidopsis thaliana were compared with the wild type (Col-0) for Mg(2+) uptake and intracellular Mg(2+) concentration under low-pH and combined low-pH/Al stresses. Magnesium accumulation in roots was measured in long-term (7 d) experiments. The Mg(2+) fluxes were measured using ion-sensitive microelectrodes at the distal elongation and the mature root zones in short-term (0-60 min) experiments. Intracellular Mg(2+) concentrations were measured in intact root cells at the distal elongation zone using magnesium-specific fluorescent dye and fluorescent lifetime imaging (FLIM) analysis. Under low-pH stress, Arabidopsis mutants als5 and alr104 maintained a higher Mg concentration in roots, and had greater Mg(2+) influx than the wild type and the als3 mutant. Under combined low-pH/Al treatment, Al-resistant genotypes (wild type and alr104) maintained a higher Mg(2+) accumulation, and had a higher Mg(2+) influx and higher intracellular Mg(2+) concentration than Al-sensitive genotypes (als3 and als5). Overall, these results show that increased Mg(2+) uptake correlates with an enhanced capacity of Arabidopsis genotypes to cope with low-pH and combined low-pH/Al stresses.
Publisher: CSIRO Publishing
Date: 2016
DOI: 10.1071/FP16135
Abstract: The effects of NaCl stress and K+ nutrition on photosynthetic parameters of isolated chloroplasts were investigated using PAM fluorescence. Intact mesophyll cells were able to maintain optimal photosynthetic performance when exposed to salinity for more than 24 h whereas isolated chloroplasts showed declines in both the relative electron transport rate (rETR) and the maximal photochemical efficiency of PSII (Fv/Fm) within the first hour of treatment. The rETR was much more sensitive to salt stress compared with Fv/Fm, with 40% inhibition of rETR observed at apoplastic NaCl concentration as low as 20 mM. In isolated chloroplasts, absolute K+ concentrations were more essential for the maintenance of the optimal photochemical performance (Fv/Fm values) rather than sodium concentrations per se. Chloroplasts from halophyte species of quinoa (Chenopodium quinoa Willd.) and pigface (Carpobrotus rosii (Haw.) Schwantes) showed less than 18% decline in Fv/Fm under salinity, whereas the Fv/Fm decline in chloroplasts from glycophyte pea (Pisum sativum L.) and bean (Vicia faba L.) species was much stronger (31 and 47% respectively). Vanadate (a P-type ATPase inhibitor) significantly reduced Fv/Fm in both control and salinity treated chloroplasts (by 7 and 25% respectively), whereas no significant effects of gadolinium (blocker of non-selective cation channels) were observed in salt-treated chloroplasts. Tetraethyl ammonium (TEA) (K+ channel inhibitor) and amiloride (inhibitor of the Na+/H+ antiporter) increased the Fv/Fm of salinity treated chloroplasts by 16 and 17% respectively. These results suggest that chloroplasts’ ability to regulate ion transport across the envelope and thylakoid membranes play a critical role in leaf photosynthetic performance under salinity.
Publisher: Springer International Publishing
Date: 2015
Publisher: Springer Science and Business Media LLC
Date: 29-07-2015
DOI: 10.1038/NCOMMS8879
Abstract: The non-protein amino acid, gamma-aminobutyric acid (GABA) rapidly accumulates in plant tissues in response to biotic and abiotic stress, and regulates plant growth. Until now it was not known whether GABA exerts its effects in plants through the regulation of carbon metabolism or via an unidentified signalling pathway. Here, we demonstrate that anion flux through plant aluminium-activated malate transporter (ALMT) proteins is activated by anions and negatively regulated by GABA. Site-directed mutagenesis of selected amino acids within ALMT proteins abolishes GABA efficacy but does not alter other transport properties. GABA modulation of ALMT activity results in altered root growth and altered root tolerance to alkaline pH, acid pH and aluminium ions. We propose that GABA exerts its multiple physiological effects in plants via ALMT, including the regulation of pollen tube and root growth, and that GABA can finally be considered a legitimate signalling molecule in both the plant and animal kingdoms.
Publisher: Oxford University Press (OUP)
Date: 02-12-2014
DOI: 10.1093/AOB/MCU219
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: Wiley
Date: 24-03-2011
DOI: 10.1111/J.1365-3040.2011.02296.X
Abstract: This work investigates the role of cytosolic Na+ exclusion in roots as a means of salinity tolerance in wheat, and offers in planta methods for the functional assessment of major transporters contributing to this trait. An electrophysiological protocol was developed to quantify the activity of plasma membrane Na+ efflux systems in roots, using the microelectrode ion flux estimation (MIFE) technique. We show that active efflux of Na+ from wheat root epidermal cells is mediated by a SOS1-like homolog, energized by the plasma membrane H+-ATPase. SOS1-like efflux activity was highest in Kharchia 65, a salt-tolerant bread wheat cultivar. Kharchia 65 also had an enhanced ability to sequester large quantities of Na+ into the vacuoles of root cells, as revealed by confocal microscopy using Sodium Green. These findings were consistent with the highest level of expression of both SOS1 and NHX1 transcripts in plant roots in this variety. In the sensitive wheat varieties, a greater proportion of Na+ was located in the root cell cytosol. Overall, our findings suggest a critical role of cytosolic Na+ exclusion for salinity tolerance in wheat and offer convenient protocols to quantify the contribution of the major transporters conferring this trait, to screen plants for salinity tolerance.
Publisher: MDPI AG
Date: 04-2019
DOI: 10.3390/PH12020049
Abstract: Essential oil from the leaves of Artemisia vulgaris L. (Compositae) cultivated in Brazil was investigated for its chemical composition and biological activities including antibacterial, antifungal, and anthelmintic. The constituents of essential oils isolated by hydro-distillation were examined by GC-MS and a total of 18 components were identified. The essential oil was dominated by oxygenated sesquiterpenes (44.4%), sesquiterpene hydrocarbons (33.3%), and oxygenated monoterpenes (16.6%). Caryophyllene (37.45%), germacrene D (16.17%), and humulene (13.66%) were the major components. The essential oils from A. vulgaris showed bactericidal and fungicidal properties against Staphylococcus aureus and Candida albicans, respectively. Anthelmintic activity against Haemonchus contortus was absent in this essential oil. Altogether above results indicate that essential oils from A. vulgaris can be used for various medicinal purposes.
Publisher: MDPI AG
Date: 10-07-2020
DOI: 10.3390/IJMS21144882
Abstract: In rice, the OsHKT1 gene has been reported to be a critical determinant of salt tolerance. This gene is harbored by the SKC1 locus, and its role was attributed to Na+ unloading from the xylem. No direct evidence, however, was provided in previous studies. Also, the reported function of SKC1 on the loading and delivery of K+ to the shoot remains to be explained. In this work, we used an electrophysiological approach to compare the kinetics of Na+ uptake by root xylem parenchyma cells using wild type (WT) and NIL(SKC1) plants. Our data showed that Na+ reabsorption was observed in WT, but not NIL(SKC1) plants, thus questioning the functional role of HKT1 as a transporter operating in the direct Na+ removal from the xylem. Instead, changes in the expression level of HKT1 altered the activity of membrane transporters involved in K+ and Ca2+ acquisition and homeostasis in the rice epidermis and stele, explaining the observed phenotype. We conclude that the role of HKT1 in plant salinity tolerance cannot be attributed to merely reducing Na+ concentration in the xylem sap but triggers a complex feedback regulation of activities of other transporters involved in the maintenance of plant ionic homeostasis and signaling under stress conditions.
Publisher: Oxford University Press (OUP)
Date: 23-05-2010
DOI: 10.1093/JXB/ERQ143
Publisher: Cold Spring Harbor Laboratory
Date: 24-01-2020
DOI: 10.1101/2020.01.21.909887
Abstract: Improving salinity tolerance in the most widely cultivated cereal, bread wheat ( Triticum aestivum L.), is essential to increase grain yields on saline agricultural lands. A Portuguese landrace, Mocho de Espiga Branca accumulates up to 6 folds greater leaf and sheath sodium (Na + ) than two Australian cultivars, Gladius and Scout, under salt stress. Despite high leaf and sheath Na + concentrations, Mocho de Espiga Branca maintained similar salinity tolerance compared to Gladius and Scout. A naturally occurring single nucleotide substitution was identified in the gene encoding a major Na + transporter TaHKT1 -D in Mocho de Espiga Branca, which resulted in a L190P amino acid residue variation. This variant prevents Mocho de Espiga Branca from retrieving Na + from the root xylem leading to a high shoot Na + concentration. The identification of the tissue tolerant Mocho de Espiga Branca will accelerate the development of more elite salt tolerant bread wheat cultivars.
Publisher: Springer International Publishing
Date: 2018
Publisher: Springer Science and Business Media LLC
Date: 23-01-2015
Start Date: 2017
End Date: 2020
Funder: Australian Research Council
View Funded ActivityStart Date: 06-2017
End Date: 06-2020
Amount: $372,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 06-2022
End Date: 07-2026
Amount: $802,000.00
Funder: Australian Research Council
View Funded Activity