ORCID Profile
0000-0001-8466-4186
Current Organisation
Monash 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 biochemistry | Agricultural molecular engineering of nucleic acids and proteins | Plant biology | Plant physiology
Publisher: Bio-Protocol, LLC
Date: 2015
Publisher: Elsevier BV
Date: 03-2012
DOI: 10.1016/J.ECOENV.2011.10.001
Abstract: The aim of this research was to evaluate possible toxic effects of commercial formulation containing fipronil on Cyprinus carpio tissues under rice field conditions. Antioxidant profile (SOD, catalase, glutathione S-transferase), oxidative stress parameters (thiobarbituric acid-reactive substances, protein carbonyl), and growth were investigated in carp exposed to fipronil under rice field conditions for 7, 30, and 90 days. Waterborne insecticide concentrations were measured and the detectable concentration of fipronil was observed up to 45 day after application. Common carp survival and growth was not affected by fipronil. Liver superoxide dismutase activity was enhanced while liver catalase activity was inhibited at 7, 30, and 90 days. Alterations were not observed in the glutathione S-transferase activity in any experimental periods. Protein carbonyl increased only after 30 and 90 days of exposure. The thiobarbituric acid-reactive substances levels were enhanced in all analyzed tissues (liver, muscle, and brain) and periods of exposure. This study demonstrates that fipronil insecticides cause alterations in the biochemical parameters in different tissues of carp without affecting the growth or the survival of the fish.
Publisher: Cold Spring Harbor Laboratory
Date: 10-05-2022
DOI: 10.1101/2022.05.09.491242
Abstract: Sedoheptulose-1,7-bisphosphatase (SBPase) is one of the rate-limiting enzymes of the Calvin cycle, and, in C 3 plants, increasing the abundance of SBPase is known to provide higher photosynthetic rates and stimulate biomass and yield. C 4 plants usually have higher photosynthetic rates because they operate a biochemical CO 2 concentrating mechanism between mesophyll and bundle sheath cells. In the C 4 system, SBPase and other enzymes of Calvin cycle are localised to the bundle sheath cells. Here we tested what effect increasing abundance of SBPase would have on C 4 photosynthesis. Using Setaria viridis , a model C 4 plant of NADP-ME subtype, we created transgenic plants with 1.5 to 3.2-times higher SBPase content, compared to wild type plants. Transcripts of the transgene were found predominantly in the bundle sheaths suggesting the correct cellular localisation of the protein. Abundance of RBCL, the large subunit of Rubisco, was not affected in transgenic plants overexpressing SBPase, and neither was relative chlorophyll content or photosynthetic electron transport parameters. We found no correlation between SBPase content in S. viridis and saturating rates of CO 2 assimilation. Moreover, detailed analysis of CO 2 assimilation rates at different CO 2 partial pressure, irradiance and leaf temperature, showed no improvement of photosynthesis in plants overexpressing SBPase. We discuss potential implications of these results for understanding the regulation of C 4 photosynthesis.
Publisher: Springer Science and Business Media LLC
Date: 06-1997
DOI: 10.1038/42355
Publisher: Wiley
Date: 31-08-2022
DOI: 10.1111/TPJ.15915
Abstract: When C 4 leaves are exposed to low light, the CO 2 concentration in the bundle sheath (BS) cells decreases, causing an increase in photorespiration relative to assimilation, and a consequent reduction in biochemical efficiency. These effects can be mitigated by complex acclimation syndromes, which are of primary importance for crop productivity but are not well studied. We unveil an acclimation strategy involving the coordination of electron transport processes. First, we characterize the anatomy, gas exchange and electron transport of C 4 Setaria viridis grown under low light. Through a purposely developed biochemical model, we resolve the photon fluxes and reaction rates to explain how the concerted acclimation strategies sustain photosynthetic efficiency. Our results show that a smaller BS in low‐light‐grown plants limited leakiness (the ratio of CO 2 leak rate out of the BS over the rate of supply via C 4 acid decarboxylation) but sacrificed light harvesting and ATP production. To counter ATP shortage and maintain high assimilation rates, plants facilitated light penetration through the mesophyll and upregulated cyclic electron flow in the BS. This shade tolerance mechanism, based on the optimization of light reactions, is possibly more efficient than the known mechanisms involving the rearrangement of carbon metabolism, and could potentially lead to innovative strategies for crop improvement.
Publisher: Cold Spring Harbor Laboratory
Date: 29-04-2021
DOI: 10.1101/2021.04.28.441895
Abstract: A fundamental limitation of photosynthetic carbon fixation is the availability of CO 4 . In C 4 plants, primary carboxylation occurs in mesophyll cytosol, and little is known about the role of CO 2 diffusion in facilitating C 4 photosynthesis. We have examined the expression, localization, and functional role of selected plasma membrane intrinsic aquaporins (PIPs) from Setaria italica (foxtail millet) and discovered that SiPIP2 is CO 2 -permeable. When ectopically expressed in mesophyll cells of S. viridis (green foxtail), SiPIP2 was localized to the plasma membrane and caused no marked changes in leaf biochemistry. Gas-exchange and C 18 O 16 O discrimination measurements revealed that targeted expression of SiPIP2 enhanced the conductance to CO 2 diffusion from the intercellular airspace to the mesophyll cytosol. Our results demonstrate that mesophyll conductance limits C 4 photosynthesis at low p CO 2 and that SiPIP2 is a functional CO 2 permeable aquaporin that can improve CO 2 diffusion at the airspace/mesophyll interface and enhance C 4 photosynthesis.
Publisher: Cold Spring Harbor Laboratory
Date: 11-04-2021
DOI: 10.1101/2021.04.11.439306
Abstract: When C 4 leaves are exposed to low light, CO 2 concentration in the bundle sheath (BS) cells decreases, causing an increase in photorespiration relative to assimilation, and a consequent reduction in biochemical efficiency. These effects can be mitigated by complex acclimation syndromes, which are of primary importance for crop productivity, but not well studied. We unveil an acclimation strategy involving regulation of electron transport processes. Firstly, we characterise anatomy, gas-exchange and electron transport of C 4 Setaria viridis grown under low light. Through a purposely developed biochemical model, we resolve the photon fluxes and reaction rates to explain how the concerted acclimation strategies sustain photosynthetic efficiency. Our results show that a smaller BS in low light-grown plants limited leakiness (the ratio of CO 2 leak rate out of the BS over the rate of supply via C 4 acid decarboxylation) but sacrificed light harvesting and ATP production. To counter ATP shortage and maintain high assimilation rates, plants facilitated light penetration through the mesophyll and upregulated cyclic electron flow in the BS. This shade tolerance mechanism based on optimisation of light reactions is potentially more efficient than the known mechanisms involving the rearrangement of carbon metabolism, and can potentially lead to innovative strategies for crop improvement. We mechanistically link the optical cross-section of leaf compartments with the rate of electron transport, the engagement of cyclic electron flow, the relative rate of ATP and NADPH generation, and fluxes through the carbon metabolism. The striking capacity of Setaria viridis to counter the decrease in light absorption in the bundle sheath with an increase of cyclic electron flow presents perhaps the most efficient mechanism of shade acclimation.
Publisher: Cold Spring Harbor Laboratory
Date: 17-09-2023
Publisher: Proceedings of the National Academy of Sciences
Date: 07-07-2014
Abstract: Cyanobacterial flavodiiron proteins (FDPs) comprise a protein family with unique modular structure and photoprotective functions in an oxygenic environment. It is conceivable that FDPs have made the development of oxygenic photosynthesis possible in cyanobacteria. Here, we report the ability of specific FDPs to reduce O 2 directly to water in heterocyst-forming filamentous cyanobacteria, not only to support the photosynthetic machinery, but also to prevent oxidative damage of the N 2 -fixing enzyme nitrogenase. Whilst in the ancient environment, N 2 fixation was secured from O 2 inhibition, the later increase of atmospheric O 2 may have initiated an important role for FDP-mediated protection of nitrogenase in maintaining the N 2 -fixing activity of cyanobacteria.
Publisher: eLife Sciences Publications, Ltd
Date: 17-10-2021
Publisher: Wiley
Date: 14-11-2020
DOI: 10.1111/TPJ.14562
Publisher: Cold Spring Harbor Laboratory
Date: 10-02-2021
DOI: 10.1101/2021.02.10.430537
Abstract: C 4 photosynthesis is a biochemical pathway that operates across mesophyll and bundle sheath (BS) cells to increase CO 2 concentration at the site of CO 2 fixation. C 4 plants benefit from high irradiance but their efficiency decreases under shade causing a loss of productivity in crop canopies. We investigated shade acclimation responses of a model NADP-ME monocot Setaria viridis focussing on cell-specific electron transport capacity. Plants grown under low light (LL) maintained CO 2 assimilation rates similar to high light plants but had an increased chlorophyll and light-harvesting-protein content, predominantly in BS cells. Photosystem II (PSII) protein abundance, oxygen-evolving activity and the PSII/PSI ratio all increased in LL BS cells indicating a higher capacity for linear electron flow. PSI, ATP synthase, Cytochrome b 6 f and the chloroplastic NAD(P) dehydrogenase complex, which constitute the BS cyclic electron flow machinery, were all upregulated in LL plants. A decline in PEP carboxylase activity in mesophyll cells and a consequent shortage of reducing power in BS chloroplasts was associated with the more oxidised redox state of the plastoquinone pool in LL plants and the formation of PSII - light-harvesting complex II supercomplexes with an increased oxygen evolution rate. Our results provide evidence of a redox regulation of the supramolecular composition of Photosystem II in BS cells in response to shading. This newly identified link contributes to understanding the regulation of PSII activity in C 4 plants and will support strategies for crop improvement including the engineering of C 4 photosynthesis into C 3 plants. The efficiency of C 4 photosynthesis decreases under low irradiance causing a loss of productivity in crop canopies. We investigate shade acclimation of a model NADP-ME monocot, analysing cell-specific protein expression and electron transport capacity. We propose a regulatory pathway controlling abundance and activity of Photosystem II in bundle sheath cells in response to irradiance.
Publisher: eLife Sciences Publications, Ltd
Date: 29-11-2021
DOI: 10.7554/ELIFE.70095
Abstract: A fundamental limitation of photosynthetic carbon fixation is the availability of CO 2 . In C 4 plants, primary carboxylation occurs in mesophyll cytosol, and little is known about the role of CO 2 diffusion in facilitating C 4 photosynthesis. We have examined the expression, localization, and functional role of selected plasma membrane intrinsic aquaporins (PIPs) from Setaria italica (foxtail millet) and discovered that SiPIP2 is CO 2 -permeable. When ectopically expressed in mesophyll cells of Setaria viridis (green foxtail), SiPIP2 was localized to the plasma membrane and caused no marked changes in leaf biochemistry. Gas exchange and C 18 O 16 O discrimination measurements revealed that targeted expression of SiPIP2 enhanced the conductance to CO 2 diffusion from the intercellular airspace to the mesophyll cytosol. Our results demonstrate that mesophyll conductance limits C 4 photosynthesis at low p CO 2 and that SiPIP2 is a functional CO 2 permeable aquaporin that can improve CO 2 diffusion at the airspace/mesophyll interface and enhance C 4 photosynthesis.
Publisher: Elsevier BV
Date: 07-2011
Publisher: Cold Spring Harbor Laboratory
Date: 16-12-2021
DOI: 10.1101/2021.12.15.472848
Abstract: The model heterocyst-forming filamentous cyanobacterium, Anabaena sp. PCC 7120 ( Anabaena ) represents multicellular organisms capable of simultaneously performing oxygenic photosynthesis in vegetative cells and the O 2 -sensitive N 2 -fixation inside the heterocysts. The flavodiiron proteins (FDPs) have been shown to participate in photoprotection of photosynthesis by driving excess electrons to O 2 (Mehler-like reaction). Here, we addressed the physiological relevance of the vegetative cell-specific Flv1A and Flv3A on the bioenergetic processes occurring in diazotrophic Anabaena under variable CO 2 . We demonstrate that both Flv1A and Flv3A are required for proper induction of the Mehler-like reaction upon a sudden increase in light intensity, which is likely important for the activation of carbon-concentrating mechanisms (CCM) and CO 2 fixation. Under ambient CO 2 diazotrophic conditions, Flv3A is capable of mediating moderate O 2 photoreduction, independently of Flv1A, but in coordination with Flv2 and Flv4. Strikingly, the lack of Flv3A resulted in strong downregulation of the heterocyst-specific uptake hydrogenase, which led to enhanced H 2 photoproduction under both oxic and micro-oxic conditions. These results reveal a novel regulatory network between the Mehler-like reaction and the diazotrophic metabolism, which is of great interest for future biotechnological applications.
Publisher: Cold Spring Harbor Laboratory
Date: 23-12-2019
DOI: 10.1101/2019.12.23.886929
Abstract: In oxygenic photosynthetic organisms excluding angiosperms, flavodiiron proteins (FDPs) catalyze light-dependent reduction of O 2 to H 2 O. This alleviates electron pressure on the photosynthetic apparatus and protects it from photodamage. In Synechocystis sp. PCC 6803, four FDP isoforms function as hetero-oligomers of Flv1 and Flv3 and/or Flv2 and Flv4. An alternative electron transport pathway mediated by the NAD(P)H dehydrogenase-like complex (NDH-1) also contributes to redox hemostasis and the photoprotection of photosynthesis. Four NDH-1 types haven been characterized in cyanobacteria: NDH-1 1 and NDH-1 2 , which function in respiration and NDH-1 3 and NDH-1 4 , which function in CO 2 uptake. All four types are involved in cyclic electron transport. Along with single FDP mutants (Δ flv1 and Δ flv3 ) and the double NDH-1 mutants (Δ d1d2 , which is deficient in NDH-1 1,2 and Δ d3d4 , which is deficient in NDH-1 3,4 ), we studied triple mutants lacking either one of Flv1 or Flv3, and NDH-1 1,2 or NDH-1 3,4 . We show that the presence of either Flv1/3 or NDH-1 1,2 , but not NDH-1 3,4 , is indispensable for survival during changes in growth conditions from high CO 2 /moderate light to low CO 2 / high light. Our results suggest functional redundancy and crosstalk between FDPs and NDH-1 1,2 under the studied conditions, and demonstrate that the functions of FDPs and NDH-1 1,2 are dynamically coordinated for the efficient oxidation of PSI and for photoprotection under variable CO 2 and light availability. Flavodiiron proteins and NDH-1 complex ensure survival of cyanobacterial cells by cooperatively safeguarding the photosynthetic apparatus against excessive reduction
Publisher: Oxford University Press (OUP)
Date: 10-2019
DOI: 10.1105/TPC.19.00272
Publisher: Proceedings of the National Academy of Sciences
Date: 04-02-2013
Abstract: Cyanobacterial flavodiiron proteins (FDPs A-type flavoprotein, Flv) comprise, besides the β-lactamase–like and flavodoxin domains typical for all FDPs, an extra NAD(P)H:flavin oxidoreductase module and thus differ from FDPs in other Bacteria and Archaea. Synechocystis sp. PCC 6803 has four genes encoding the FDPs. Flv1 and Flv3 function as an NAD(P)H:oxygen oxidoreductase, donating electrons directly to O 2 without production of reactive oxygen species. Here we show that the Flv1 and Flv3 proteins are crucial for cyanobacteria under fluctuating light, a typical light condition in aquatic environments. Under constant-light conditions, regardless of light intensity, the Flv1 and Flv3 proteins are dispensable. In contrast, under fluctuating light conditions, the growth and photosynthesis of the Δ flv1(A) and/or Δ flv3(A) mutants of Synechocystis sp. PCC 6803 and Anabaena sp. PCC 7120 become arrested, resulting in cell death in the most severe cases. This reaction is mainly caused by malfunction of photosystem I and oxidative damage induced by reactive oxygen species generated during abrupt short-term increases in light intensity. Unlike higher plants that lack the FDPs and use the Proton Gradient Regulation 5 to safeguard photosystem I, the cyanobacterial homolog of Proton Gradient Regulation 5 is shown not to be crucial for growth under fluctuating light. Instead, the unique Flv1/Flv3 heterodimer maintains the redox balance of the electron transfer chain in cyanobacteria and provides protection for photosystem I under fluctuating growth light. Evolution of unique cyanobacterial FDPs is discussed as a prerequisite for the development of oxygenic photosynthesis.
Publisher: Wiley
Date: 02-03-2023
DOI: 10.1111/PBI.14030
Abstract: Sorghum is one of the most important crops providing food and feed in many of the world's harsher environments. Sorghum utilizes the C 4 pathway of photosynthesis in which a biochemical carbon‐concentrating mechanism results in high CO 2 assimilation rates. Overexpressing the Rieske FeS subunit of the Cytochrome b 6 f complex was previously shown to increase the rate of photosynthetic electron transport and stimulate CO 2 assimilation in the model C 4 plant Setaria viridis . To test whether productivity of C 4 crops could be improved by Rieske overexpression, we created transgenic Sorghum bicolor Tx430 plants with increased Rieske content. The transgenic plants showed no marked changes in abundances of other photosynthetic proteins or chlorophyll content. The steady‐state rates of electron transport and CO 2 assimilation did not differ between the plants with increased Rieske abundance and control plants, suggesting that Cytochrome b 6 f is not the only factor limiting electron transport in sorghum at high light and high CO 2 . However, faster responses of non‐photochemical quenching as well as an elevated quantum yield of Photosystem II and an increased CO 2 assimilation rate were observed from the plants overexpressing Rieske during the photosynthetic induction, a process of activation of photosynthesis upon the dark–light transition. As a consequence, sorghum with increased Rieske content produced more biomass and grain when grown in glasshouse conditions. Our results indicate that increasing Rieske content has potential to boost productivity of sorghum and other C 4 crops by improving the efficiency of light utilization and conversion to biomass through the faster induction of photosynthesis.
Publisher: Wiley
Date: 16-06-2020
DOI: 10.1111/TPJ.14812
Abstract: In oxygenic photosynthetic organisms, excluding angiosperms, flavodiiron proteins (FDPs) catalyze light‐dependent reduction of O 2 to H 2 O. This alleviates electron pressure on the photosynthetic apparatus and protects it from photodamage. In Synechocystis sp. PCC 6803, four FDP isoforms function as hetero‐oligomers of Flv1 and Flv3 and/or Flv2 and Flv4. An alternative electron transport pathway mediated by the NAD(P)H dehydrogenase‐like complex (NDH‐1) also contributes to redox hemostasis and the photoprotection of photosynthesis. Four NDH‐1 types have been characterized in cyanobacteria: NDH‐1 1 and NDH‐1 2 , which function in respiration and NDH‐1 3 and NDH‐1 4 , which function in CO 2 uptake. All four types are involved in cyclic electron transport. Along with single FDP mutants (∆ flv1 and Δ flv3 ) and the double NDH‐1 mutants (∆ d1d2 , which is deficient in NDH‐1 1,2 and ∆ d3d4 , which is deficient in NDH‐1 3,4 ), we studied triple mutants lacking one of Flv1 or Flv3, and NDH‐1 1,2 or NDH‐1 3,4 . We show that the presence of either Flv1/3 or NDH‐1 1,2 , but not NDH‐1 3,4 , is indispensable for survival during changes in growth conditions from high CO 2 /moderate light to low CO 2 /high light. Our results show functional redundancy between FDPs and NDH‐1 1,2 under the studied conditions. We suggest that ferredoxin probably functions as a primary electron donor to both Flv1/3 and NDH‐1 1,2 , allowing their functions to be dynamically coordinated for efficient oxidation of photosystem I and for photoprotection under variable CO 2 and light availability.
Publisher: Wiley
Date: 24-06-2022
DOI: 10.1111/PBI.13864
Abstract: In biological discovery and engineering research, there is a need to spatially and/or temporally regulate transgene expression. However, the limited availability of promoter sequences that are uniquely active in specific tissue‐types and/or at specific times often precludes co‐expression of multiple transgenes in precisely controlled developmental contexts. Here, we developed a system for use in rice that comprises synthetic designer transcription activator‐like effectors (dTALEs) and cognate synthetic TALE‐activated promoters (STAPs). The system allows multiple transgenes to be expressed from different STAPs, with the spatial and temporal context determined by a single promoter that drives expression of the dTALE. We show that two different systems—dTALE1‐STAP1 and dTALE2‐STAP2—can activate STAP‐driven reporter gene expression in stable transgenic rice lines, with transgene transcript levels dependent on both dTALE and STAP sequence identities. The relative strength of in idual STAP sequences is consistent between dTALE1 and dTALE2 systems but differs between cell‐types, requiring empirical evaluation in each case. dTALE expression leads to off‐target activation of endogenous genes but the number of genes affected is substantially less than the number impacted by the somaclonal variation that occurs during the regeneration of transformed plants. With the potential to design fully orthogonal dTALEs for any genome of interest, the dTALE‐STAP system thus provides a powerful approach to fine‐tune the expression of multiple transgenes, and to simultaneously introduce different synthetic circuits into distinct developmental contexts.
Publisher: Springer Science and Business Media LLC
Date: 16-08-2019
DOI: 10.1038/S42003-019-0561-9
Abstract: C 4 photosynthesis is characterised by a CO 2 concentrating mechanism that operates between mesophyll and bundle sheath cells increasing CO 2 partial pressure at the site of Rubisco and photosynthetic efficiency. Electron transport chains in both cell types supply ATP and NADPH for C 4 photosynthesis. Cytochrome b 6 f is a key control point of electron transport in C 3 plants. To study whether C 4 photosynthesis is limited by electron transport we constitutively overexpressed the Rieske FeS subunit in Setaria viridis . This resulted in a higher Cytochrome b 6 f content in mesophyll and bundle sheath cells without marked changes in the abundances of other photosynthetic proteins. Rieske overexpression plants showed better light conversion efficiency in both Photosystems and could generate higher proton-motive force across the thylakoid membrane underpinning an increase in CO 2 assimilation rate at ambient and saturating CO 2 and high light. Our results demonstrate that removing electron transport limitations can increase C 4 photosynthesis.
Publisher: Oxford University Press (OUP)
Date: 29-07-2022
DOI: 10.1093/JXB/ERAC320
Abstract: ATP, produced by the light reactions of photosynthesis, acts as the universal cellular energy cofactor fuelling all life processes. Chloroplast ATP synthase produces ATP using the proton motive force created by solar energy-driven thylakoid electron transport reactions. Here we investigate how increasing abundance of ATP synthase affects leaf photosynthesis and growth of rice, Oryza sativa variety Kitaake. We show that overexpression of AtpD, the nuclear-encoded subunit of the chloroplast ATP synthase, stimulates both abundance of the complex, confirmed by immunodetection of thylakoid complexes separated by Blue Native-PAGE, and ATP synthase activity, detected as higher proton conductivity of the thylakoid membrane. Plants with increased AtpD content had higher CO2 assimilation rates when a stepwise increase in CO2 partial pressure was imposed on leaves at high irradiance. Fitting of the CO2 response curves of assimilation revealed that plants overexpressing AtpD had a higher electron transport rate (J) at high CO2, despite having wild-type-like abundance of the cytochrome b6f complex. A higher maximum carboxylation rate (Vcmax) and lower cyclic electron flow detected in transgenic plants both pointed to an increased ATP production compared with wild-type plants. Our results present evidence that the activity of ATP synthase modulates the rate of electron transport at high CO2 and high irradiance.
Publisher: Cold Spring Harbor Laboratory
Date: 12-03-2019
DOI: 10.1101/574897
Abstract: C 4 plants contribute 20% to the global primary productivity despite representing only 4% of higher plant species. Their CO 2 concentrating mechanism operating between mesophyll and bundle sheath cells increases CO 2 partial pressure at the site of Rubisco and hence photosynthetic efficiency. Electron transport chains in both cell types supply ATP and NADPH for C 4 photosynthesis. Since Cytochrome b 6 f is a key point of control of electron transport in C 3 plants, we constitutively overexpressed the Rieske FeS subunit in Setaria viridis to study the effects on C 4 photosynthesis. Rieske FeS overexpression resulted in a higher content of Cytochrome b 6 f in both mesophyll and bundle sheath cells without marked changes in abundances of other photosynthetic complexes and Rubisco. Plants with higher Cytochrome b 6 f abundance showed better light conversion efficiency in both Photosystems and could generate higher proton-motive force across the thylakoid membrane. Rieske FeS abundance correlated with CO 2 assimilation rate and plants with a 10% increase in Rieske FeS content showed a 10% increase in CO 2 assimilation rate at ambient and saturating CO 2 and high light. Our results demonstrate that Cytochrome b 6 f controls the rate of electron transport in C 4 plants and that removing electron transport limitations can increase the rate of C 4 photosynthesis.
Publisher: Springer Science and Business Media LLC
Date: 09-08-2013
DOI: 10.1007/S00244-013-9944-Y
Abstract: Triphenyltin (TPhT) is used worldwide in pesticide formulas for agriculture. Toxic effects of this compound to aquatic life have been reported however, the biochemical response of fish exposed to different concentrations of TPhT hydroxide (TPhTH) was investigated for the first time in this study. The lethal concentration (LC50) of TPhTH to silver catfish, Rhamdia quelen, was calculated from an acute-exposure experiment (96 h). In addition, acethylcholinesterase (AChE) activity in brain and muscle-as well as glucose, glycogen, lactate, total protein, ammonia, and free amino acids in liver and muscle-were evaluated in a chronic-exposure experiment (15-day exposure). Speciation analysis of tin (Sn) was performed in fish tissues at the end of both experiments using gas chromatography coupled to a pulsed-flame photometric detector (GC-PFPD). Concentrations of TPhT, diphenyltin, and monophenyltin (reported as Sn) were lower than limits of quantification (10σ criteria). Waterborne TPhTH concentration used through the experiment was also evaluated by GC-PFPD, and no degradation of this species was observed. The LC50 value for silver catfish juveniles was 9.73 μg L(-1) (as Sn). Decreased brain and muscle AChE activities were observed in fish exposed to TPhTH in relation to unexposed fish (control). Liver glycogen and lactate levels were significantly higher in fish kept at the highest waterborne TPhTH concentration compared with the control. Liver and muscle glucose levels of fish exposed to all TPhTH concentrations were significantly lower than those of control fish. Silver catfish exposed to all TPhTH concentrations showed lower total protein values and higher total free amino acids levels in liver and muscle compared with controls. Total ammonia levels in liver and muscle were significantly higher for the highest TPhTH concentration compared with controls. In conclusion, TPhTH caused metabolic alterations in silver catfish juveniles, and the analyzed parameters can also be used as bioindicators for TPhTH contamination.
Publisher: Oxford University Press (OUP)
Date: 18-04-2016
DOI: 10.1104/PP.16.00479
Publisher: Springer Science and Business Media LLC
Date: 20-02-2017
DOI: 10.1007/S10646-017-1780-9
Abstract: Among all organotin compounds , triphenyltin hydroxide (TPhTH) is widely used as fungicide and moluscicide in Brazil. However, the effects of TPhTH on the biochemical parameters of non-target organisms, such as fish, are little known. The aim of the present study is to assess the possible toxic effects of different concentrations of waterborne TPhTH on silver catfish belonging to species Rhamdia quelen. The fish were exposed to two different concentrations of TPhTH (1.08 and 1.70 µg/L as Sn) for 15 days and then compared to the control group (triplicate, n = 3). The antioxidant profile (catalase (CAT) and the glutathione S-transferase (GST)) and the oxidative stress parameters (TBARS-thiobarbituric acid-reactive substances and protein carbonyl (PC)) were set after the exposure to TPhTH. The TBARS level and the PC content increased in several organs of the Rhamdia quelen (brain, liver, muscle and gills) under the two concentrations of TPhTH in comparison to the control group. The CAT activity in the liver and gills has enhanced in all tested TPhTH concentrations. The GST activity increased in the brain, liver and muscle tissues under all the TPhTH concentrations. The significant changes in the biomarkers indicated that the investigated pesticide could have harmful effect on fish, in the field. However, these biomarkers were measured after the fish received doses lower than the recommended for use in agriculture.
Publisher: Wiley
Date: 07-05-2021
DOI: 10.1111/TPJ.15247
Abstract: C 4 photosynthesis is a biochemical pathway that operates across mesophyll and bundle sheath (BS) cells to increase CO 2 concentration at the site of CO 2 fixation. C 4 plants benefit from high irradiance but their efficiency decreases under shade, causing a loss of productivity in crop canopies. We investigated shade acclimation responses of Setaria viridis , a model monocot of NADP‐dependent malic enzyme subtype, focussing on cell‐specific electron transport capacity. Plants grown under low light (LL) maintained CO 2 assimilation rates similar to high light plants but had an increased chlorophyll and light‐harvesting‐protein content, predominantly in BS cells. Photosystem II (PSII) protein abundance, oxygen‐evolving activity and the PSII/PSI ratio were enhanced in LL BS cells, indicating a higher capacity for linear electron flow. Abundances of PSI, ATP synthase, Cytochrome b 6 f and the chloroplast NAD(P)H dehydrogenase complex, which constitute the BS cyclic electron flow machinery, were also increased in LL plants. A decline in PEP carboxylase activity in mesophyll cells and a consequent shortage of reducing power in BS chloroplasts were associated with a more oxidised plastoquinone pool in LL plants and the formation of PSII – light‐harvesting complex II supercomplexes with an increased oxygen evolution rate. Our results suggest that the supramolecular composition of PSII in BS cells is adjusted according to the redox state of the plastoquinone pool. This discovery contributes to the understanding of the acclimation of PSII activity in C 4 plants and will support the development of strategies for crop improvement, including the engineering of C 4 photosynthesis into C 3 plants.
Publisher: Wiley
Date: 27-10-2020
DOI: 10.1111/PBI.13487
Publisher: Wiley
Date: 11-2022
DOI: 10.1111/PPL.13803
Abstract: Photosynthesis is fundamental for plant growth and yield. The cytochrome b 6 f complex catalyses a rate‐limiting step in thylakoid electron transport and therefore represents an important point of regulation of photosynthesis. Here we show that overexpression of a single core subunit of cytochrome b 6 f , the Rieske FeS protein, led to up to a 40% increase in the abundance of the complex in Nicotiana tabacum (tobacco) and was accompanied by an enhanced in vitro cytochrome f activity, indicating a full functionality of the complex. Analysis of transgenic plants overexpressing Rieske FeS by the light‐induced fluorescence transients technique revealed a more oxidised primary quinone acceptor of photosystem II ( Q A ) and plastoquinone pool and faster electron transport from the plastoquinone pool to photosystem I upon changes in irradiance, compared to control plants. A faster establishment of q E , the energy‐dependent component of nonphotochemical quenching, in transgenic plants suggests a more rapid buildup of the transmembrane proton gradient, also supporting the increased in vivo cytochrome b 6 f activity. However, there was no consistent increase in steady‐state rates of electron transport or CO 2 assimilation in plants overexpressing Rieske FeS grown in either laboratory conditions or field trials, suggesting that the in vivo activity of the complex was only transiently increased upon changes in irradiance. Our results show that overexpression of Rieske FeS in tobacco enhances the abundance of functional cytochrome b 6 f and may have the potential to increase plant productivity if combined with other traits.
Publisher: Cold Spring Harbor Laboratory
Date: 25-07-2022
DOI: 10.1101/2022.07.25.501469
Abstract: Sorghum is one of the most important crops providing food and feed in many of the world’s harsher environments. Sorghum utilises the C 4 pathway of photosynthesis in which a biochemical carbon concentrating mechanism results in high CO 2 assimilation rates. Overexpressing the Rieske subunit of the Cytochrome b 6 f complex was previously shown to increase the rate of photosynthetic electron transport and stimulate CO 2 assimilation in the model C 4 plant Setaria viridis . To test whether productivity of C 4 crops could be improved by Rieske overexpression, we created transgenic Sorghum bicolor plants with increased Rieske content. The transgenic plants showed no marked changes in abundance of other photosynthetic proteins or chlorophyll content. Increases in yield of Photosystem II and CO 2 assimilation rate as well as faster responses of non-photochemical quenching during transient photosynthetic responses were observed as a result of an elevated in vivo Cytochrome b 6 f activity in plants overexpressing Rieske. The steady-state rates of electron transport and CO 2 assimilation did not differ between transgenic and control plants, suggesting that Cytochrome b 6 f is not the only factor limiting electron transport in sorghum at high light and high CO 2 . Nevertheless, more agile responses of photosynthesis to light transitions led to increases in biomass and grain yield in plants overexpressing Rieske. Our results indicate that increasing Rieske content could boost productivity of C 4 crops by improving the efficiency of light utilisation and conversion to biomass.
Publisher: Wiley
Date: 12-12-2021
DOI: 10.1111/TPJ.15581
Abstract: Photosynthetic efficiency and sink demand are tightly correlated with rates of phloem loading, where maintaining low cytosolic sugar concentrations is paramount to prevent the downregulation of photosynthesis. Sugars Will Eventually be Exported Transporters (SWEETs) are thought to have a pivotal role in the apoplastic phloem loading of C 4 grasses. SWEETs have not been well studied in C 4 species, and their investigation is complicated by photosynthesis taking place across two cell types and, therefore, photoassimilate export can occur from either one. SWEET13 homologues in C 4 grasses have been proposed to facilitate apoplastic phloem loading. Here, we provide evidence for this hypothesis using the C 4 grass Setaria viridis . Expression analyses on the leaf gradient of C 4 species Setaria and Sorghum bicolor show abundant transcript levels for SWEET13 homologues. Carbohydrate profiling along the Setaria leaf shows total sugar content to be significantly higher in the mature leaf tip compared with the younger tissue at the base. We present the first known immunolocalization results for SvSWEET13a and SvSWEET13b using novel isoform‐specific antisera. These results show localization to the bundle sheath and phloem parenchyma cells of both minor and major veins. We further present the first transport kinetics study of C 4 monocot SWEETs by using a Xenopus laevis oocyte heterologous expression system. We demonstrate that SvSWEET13a and SvSWEET13b are high‐capacity transporters of glucose and sucrose, with a higher apparent V max for sucrose, compared with glucose, typical of clade III SWEETs. Collectively, these results provide evidence for an apoplastic phloem loading pathway in Setaria and possibly other C 4 species.
Publisher: Wiley
Date: 11-10-2022
DOI: 10.1111/NPH.18506
Abstract: The model heterocyst‐forming filamentous cyanobacterium Anabaena sp. PCC 7120 ( Anabaena ) is a typical ex le of a multicellular organism capable of simultaneously performing oxygenic photosynthesis in vegetative cells and O 2 ‐sensitive N 2 ‐fixation inside heterocysts. The flavodiiron proteins have been shown to participate in photoprotection of photosynthesis by driving excess electrons to O 2 (a Mehler‐like reaction). Here, we performed a phenotypic and biophysical characterization of Anabaena mutants impaired in vegetative‐specific Flv1A and Flv3A in order to address their physiological relevance in the bioenergetic processes occurring in diazotrophic Anabaena under variable CO 2 conditions. We demonstrate that both Flv1A and Flv3A are required for proper induction of the Mehler‐like reaction upon a sudden increase in light intensity, which is likely important for the activation of carbon‐concentrating mechanisms and CO 2 fixation. Under ambient CO 2 diazotrophic conditions, Flv3A is responsible for moderate O 2 photoreduction, independently of Flv1A, but only in the presence of Flv2 and Flv4. Strikingly, the lack of Flv3A resulted in strong downregulation of the heterocyst‐specific uptake hydrogenase, which led to enhanced H 2 photoproduction under both oxic and micro‐oxic conditions. These results reveal a novel regulatory network between the Mehler‐like reaction and the diazotrophic metabolism, which is of great interest for future biotechnological applications.
Publisher: Cold Spring Harbor Laboratory
Date: 30-06-2022
DOI: 10.1101/2022.06.28.497970
Abstract: Photosynthesis is fundamental for plant growth and yield. The Cytochrome b 6 f complex catalyses a rate-limiting step in thylakoid electron transport and therefore represents an important point of regulation of photosynthesis. Here we show that overexpression of a single core subunit of Cytochrome b 6 f , the Rieske FeS protein, led to up to a 40% increase in the abundance of the complex in Nicotiana tabacum (tobacco) and was accompanied by an enhanced in vitro Cytochrome f activity, indicating a full functionality of the complex. Analysis of transgenic plants overexpressing Rieske FeS by the light-induced fluorescence transients technique revealed a more oxidised primary quinone acceptor of Photosystem II (Q A ) and plastoquinone pool and a faster electron transport from the plastoquinone pool to Photosystem I upon changes in irradiance, compared to control plants. A faster establishing of q E , the energy-dependent component of non-photochemical quenching, in transgenic plants suggested a more rapid build-up of the transmembrane proton gradient, also supporting the increased in vivo Cytochrome b 6 f activity. However, there was no consistent increase in steady-state rates of electron transport or CO 2 assimilation in plants overexpressing Rieske FeS grown in either laboratory conditions or in field trials, suggesting that the in vivo activity of the complex was only transiently increased upon changes in irradiance. Our results show that overexpression of Rieske FeS in tobacco enhances abundance of functional Cytochrome b 6 f and electron transport capacity and may have a potential to increase plant productivity if combined with other traits. Increased abundance of Cytochrome b 6 f complex leads to transient increases in photosynthetic electron transport rate in tobacco.
Publisher: Oxford University Press (OUP)
Date: 25-10-2022
Abstract: Sedoheptulose-1,7-bisphosphatase (SBPase) is one of the rate-limiting enzymes of the Calvin cycle, and increasing the abundance of SBPase in C3 plants provides higher photosynthetic rates and stimulates biomass and yield. C4 plants usually have higher photosynthetic rates because they operate a biochemical CO2-concentrating mechanism between mesophyll and bundle sheath cells. In the C4 system, SBPase and other enzymes of the Calvin cycle are localized to the bundle sheath cells. Here we tested what effect increasing abundance of SBPase would have on C4 photosynthesis. Using green foxtail millet (Setaria viridis), a model C4 plant of NADP-ME subtype, we created transgenic plants with 1.5 to 3.2 times higher SBPase content compared to wild-type plants. Transcripts of the transgene were found predominantly in the bundle sheaths suggesting the correct cellular localization of the protein. The abundance of ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit was not affected in transgenic plants overexpressing SBPase, and neither was leaf chlorophyll content or photosynthetic electron transport parameters. We found no association between SBPase content in S. viridis and saturating rates of CO2 assimilation. Moreover, a detailed analysis of CO2 assimilation rates at different CO2 partial pressures, irradiances, and leaf temperatures showed no improvement of photosynthesis in plants overexpressing SBPase. We discuss the potential implications of these results for understanding the role of SBPase in regulation of C4 photosynthesis.
Publisher: MDPI
Date: 08-04-2020
Publisher: Wiley
Date: 21-11-2012
DOI: 10.1016/J.FEBSLET.2012.11.006
Abstract: Flavodiiron proteins present in many prokaryotic and some eukaryotic organisms have a capacity to protect cells against nitrosative or oxidative stress. In Anabaena sp. PCC 7120, Flv1 and Flv3 proteins are encoded by families of two genes. We demonstrate here that flv1A and flv3A genes are up-regulated in vegetative cells in low CO₂ and high light conditions. In contrast, flv1B and flv3B genes are expressed in N₂-fixing conditions and corresponding proteins are located exclusively in heterocysts. It is suggested that Flv1B and Flv3B protect enzymes of N₂-fixation in heterocysts of Anabaena 7120 by reducing molecular oxygen directly to water.
Start Date: 2023
End Date: 12-2025
Amount: $482,066.00
Funder: Australian Research Council
View Funded Activity