[Objectives]This study was conducted to investigate the effects of compound photorespiration inhibitors on related indexes of sweet cherry.[Methods]With the main sweet cherry variety‘Meizao’as a test material,releva...[Objectives]This study was conducted to investigate the effects of compound photorespiration inhibitors on related indexes of sweet cherry.[Methods]With the main sweet cherry variety‘Meizao’as a test material,relevant research work was carried out.[Results]Several compound photorespiration inhibitors had a better promotion effect on the photosynthetic capacity,yield and quality of sweet cherry variety‘Meizao’,and especially,the combination of 300 mg/L sodium bicarbonate,300 mg/L sodium bisulfite,300 mg/L 2,3-epoxypropionic acid and 1.5%tween-80 had the best effect.[Conclusions]The combined use of the three photorespiration inhibitors is better than the single use,and produces a good synergistic effect.展开更多
Under high light conditions, ammonium nutrition has a negative effect on plant growth. This suggests that the adverse effects of ammonium nutrition on plant growth may be related to carbon gain, photosynthesis, and ph...Under high light conditions, ammonium nutrition has a negative effect on plant growth. This suggests that the adverse effects of ammonium nutrition on plant growth may be related to carbon gain, photosynthesis, and photorespiration. However, there is no consistent evidence of a specific mechanism that could explain the plant growth reduction under ammonium supply. It is generally accepted that during the light reaction, a surplus of nicotinamide adenine dinucleotide hydrogen phosphate （NADPH） is produced, which is not completely used during the assimilation of CO2, Nitrate reduc- tion in the leaf represents an additional sink for NADPH that is not available to ammonium-grown plants. Nitrate and ammonium nutrition may use different pathways for NADPH consumption, which leads to differences in photosynthesis and photorespiration. The morphological （i.e., cell size, mesophyll thickness, and chloroplast volume） and enzymic （i.e., ribulose-1,5-bisphosphate carboxylase/oxygenase （Rubisco）, phosphoenolpyruvate carboxylase （PEPCase）, and glutamine synthetase/glutamate synthetase （GS/GOGAT）） differences that develop when plants are treated with either nitrate or ammonium nitrogen forms are related to photosynthesis and photorespiration. The differences in photorespiration rate for plants treated with nitrate or ammonium are related to the conversion of citrate to 2-oxoglutarate （2-OG） and photorespiratory CO2 refixation.展开更多
Photosynthetic rate (Pn) and the partitioning of noncyclic photosynthetic electron transport to photorespiration (Jo) in seedlings of four subtropical woody plants growing at three light intensities were studied in th...Photosynthetic rate (Pn) and the partitioning of noncyclic photosynthetic electron transport to photorespiration (Jo) in seedlings of four subtropical woody plants growing at three light intensities were studied in the summer time by measurements of chlorophyll fluorescence and CO2 exchange. Except Schima superba, an upper canopy tree species, the tree species Castanopsis fissa and two understory shrubs Psychotria rubra, Ardisia quinquegona had the highest Pn at 36% of sunlight intensity. The total photosynthetic electron transport rate (JF) and the ratio of Jo/JF were elevated in leaves under full sunlight. Jo/JF ratio reached 0.5-0.6 and coincided with the increasing of oxygenation rate of Rubisco (Vo), the activity of glycolate oxidase and photorespiration rate at full sunlight. It is suggested that an increasing partitioning proportion of photosynthetic electron transport to photorespiration might be one of the protective regulation mechanisms in forest plant under strong summer light and high temperature conditions.展开更多
In C3 plants, photorespiration is an energyexpensive process, including the oxygenation of ribulose-1,5-bisphosphate(RuBP) by ribulose 1,5-bisphosphate carboxylase/oxygenase(Rubisco) and the ensuing multiorganellar ph...In C3 plants, photorespiration is an energyexpensive process, including the oxygenation of ribulose-1,5-bisphosphate(RuBP) by ribulose 1,5-bisphosphate carboxylase/oxygenase(Rubisco) and the ensuing multiorganellar photorespiratory pathway required to recycle the toxic byproducts and recapture a portion of the fixed carbon. Photorespiration significantly impacts crop productivity through reducing yields in C3 crops by as much as 50%under severe conditions. Thus, reducing the flux through, or weive R improving the efficiency of photorespiration has the potential of large improvements in C3 crop productivity.Here, we review an array of approaches intended to engineer photorespiration in a range of plant systems with the goal of increasing crop productivity. Approaches include optimizing flux through the native photorespiratory pathway, installing non-native alternative photorespiratory pathways, and lowering or even eliminating Rubiscocatalyzed oxygenation of RuBP to reduce substrate entrance into the photorespiratory cycle. Some proposed designs have been successful at the proof of concept level.A plant systems-engineering approach, based on new opportunities available from synthetic biology to implement in silico designs, holds promise for further progress toward delivering more productive crops to farmer’s fields.展开更多
Photorespiration is a well-known CO<sub>2</sub>-evolution process accompanying photosyntheticCO<sub>2</sub> uptake, whereas its physiological significance is still not well understood. As alrea...Photorespiration is a well-known CO<sub>2</sub>-evolution process accompanying photosyntheticCO<sub>2</sub> uptake, whereas its physiological significance is still not well understood. As alreadyreported, severe photoinhibition occurred in the leaves or chloroplasts exposed to stronglight in the absence of CO<sub>2</sub> upon suppression of photorespiration, while photoinhibitioncould be prevented by the supply of CO<sub>2</sub> at a concentration near the compensation point.展开更多
The photorespiratory pathway or photorespiration is an essential process in oxygenic photosynthetic or- ganisms, which can reduce the efficiency of photosynthetic carbon assimilation and is hence frequently considered...The photorespiratory pathway or photorespiration is an essential process in oxygenic photosynthetic or- ganisms, which can reduce the efficiency of photosynthetic carbon assimilation and is hence frequently considered as a wasteful process. By comparing the response of the wild-type plants and mutants impaired in photorespiration to a shift in ambient C02 concentrations, we demonstrate that photorespiration also plays a beneficial role during short-term acclimation to reduced C02 availability. The wild-type plants re- sponded with few differentially expressed genes, mostly involved in drought stress, which is likely a conse- quence of enhanced opening of stomata and concomitant water loss upon a shift toward low C02. In contrast, mutants with impaired activity of photorespiratory enzymes were highly stressed and not able to adjust stomatal conductance to reduced external C02 availability. The transcriptional response of mutant plants was congruent, indicating a general reprogramming to deal with the consequences of reduced C02 availability, signaled by enhanced oxygenation of ribulose-l,5-bisphosphate and amplified by the artificially impaired photorespiratory metabolism. Central in this reprogramming was the pro- nounced reallocation of resources from growth processes to stress responses. Taken together, our results indicate that unrestricted photorespiratory metabolism is a prerequisite for rapid physiological acclimation to a reduction in C02 availability.展开更多
The involvement of the endoplasmic reticulum(ER)-localized adenylate transporter1(ER-ANT1)in photorespiratory metabolism has been established,yet its precise physiological function remains uncertain.Rice er-ant1 mutan...The involvement of the endoplasmic reticulum(ER)-localized adenylate transporter1(ER-ANT1)in photorespiratory metabolism has been established,yet its precise physiological function remains uncertain.Rice er-ant1 mutant plants grown in ambient air exhibited stunted growth and substantial alterations in amino acid metabolites,but recovery in a high CO_(2) condition(1.5%).We show that the absence of ERANT1 hindered the breakdown of glycine without affecting its synthesis,leading to a substantial accumulation of glycine,diminished levels of serine,and depleted reserves of glutamate and alanine.Intriguingly,the er-ant1 plants grown in high CO_(2) and later exposed to ambient air displayed reduced serine levels within 12 h,yet they accumulated serine a week after transferring to ambient air due to induced phosphorylated serine synthesis pathways.Furthermore,knockout of ER-ANT1 marginally impacted the transcription of genes governing core enzymes in photorespiration,but notably upregulated BOU expression that encodes a putative mitochondrial glutamate transporter and AGAT1 that encodes an alanine:glyoxylate aminotransferase gene.Surprisingly,AGAT1,an ER-localized protein,exhibited higher activity that correlates with the decreased alanine levels observed in the er-ant1 mutant.Lack of ER-ANT1 activity also led to a significantly elevated NADH/NAD+ratio that potentially hinders the glycine-to-serine conversion process.This supports the hypothesis that the lack of ER-ANT1-induced limitation of ATP usage might inhibit GDC activity by modulating the NADH/NAD+ratio.Moreover,non-proteinogenic amino acids,including β-alanine and γ-aminobutyrate(GABA),underwent significant alterations,even under high CO_(2) conditions in the er-ant mutant,implying additional non-photorespiration roles of ER-ANT1.Taken together,our results indicate that ER-localized ER-ANT1 plays a crucial role in amino acid metabolism during photorespiration.展开更多
In midday ginkgo ( Ginkgo biloba L.) leaves have to bear photon flux density over 1400 μmol·m -2 ·s -1 in combination with high temperatures around 35 ℃ at natural habitat. They show typical mi...In midday ginkgo ( Ginkgo biloba L.) leaves have to bear photon flux density over 1400 μmol·m -2 ·s -1 in combination with high temperatures around 35 ℃ at natural habitat. They show typical midday depression of stomatal conductance and of CO 2 assimilation rate. The zeaxanthin changes with light intensity during the day. The influence of the combination of strong light and temperature on photoinhibition was also examined in the laboratory. A low CO 2 internal conductance (31 mmol·m -2 ·s -1 ) was found in ginkgo leaves, which had been exposed to excessive light at temperature between 15 ℃ and 35 ℃ with reduced CO 2 (80 μL·L -1 ) or oxygen (2%) for 2 h, causing a low CO 2 concentration at the carboxylation site and a high proportion of photorespiration. The ratio of electron transport to CO 2 fixation was rather high in ginkgo (16 e -/CO 2 at 25 ℃) as compared with other plants. It increased with temperature also in 2% O 2 which could not be explained solely as due to change of photorespiration. The reduction of oxygen in 340 or 80 μL·L -1 CO 2 had no effect on the extent of photoinhibition at all temperatures, which indicated that electron flow caused by photorespiration in excess light was negligible in protective effect in ginkgo leaves. However, a decreased CO 2 concentration increased photoinhibition, especially at high temperature. It is concluded that the dissipation of excessive excitation energy in the PSⅡ antennae through the xanthophyll cycle may be the major protective mechanism to preventing from the deteriorated effects of strong light in ginkgo leaves.展开更多
The peculiarities of leaf carbon dioxide gas exchange in soybean genotypes grown in field over a large area and contrasting in duration of vegetation, photosynthetic traits and productivity were studied. Varietal diff...The peculiarities of leaf carbon dioxide gas exchange in soybean genotypes grown in field over a large area and contrasting in duration of vegetation, photosynthetic traits and productivity were studied. Varietal differences in the daily and ontogenetic changes in photosynthesis and photorespiration were identified. It was established that the period of the high activity of photosynthetic apparatus in high productive soybean genotypes lasts for a longer time. The photosynthetic rate and the rate of CO2 release in light due to photorespiration are higher in high productive genotypes. A value of photorespiration in contrasting soybean genotypes constitutes about 28% - 35% of photosynthetic rate. The ratio of gross photosynthesis to photorespiration in genotypes with different productivity is constant enough during ontogenesis, indicating a direct positive correlation between gross photosynthesis and photorespiration. Therefore, contrary to conception arisen during many years on the waste-fulness of photorespiration, taking into account the versatile investigations on different aspects of photo-respiration, it was proved that photorespiration is one of the evolutionarily developed vital metabolic processes in plants and the attempts to reduce this process with the purpose of increasing the crop productivity are inconsistent.展开更多
Cadmium(Cd)contamination poses a significant threat to the carbon fixation potential of farmland ecosystems,yet the molecular mechanisms underlying its inhibitory effects remain poorly understood.This study reveals th...Cadmium(Cd)contamination poses a significant threat to the carbon fixation potential of farmland ecosystems,yet the molecular mechanisms underlying its inhibitory effects remain poorly understood.This study reveals that Cd competitively binds to ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco),the key enzyme in photosynthetic carbon fixation,by displacing its native co-factor,magnesium(Mg).Both Cd^(2+)and Mg^(2+)bind to identical sites on Rubisco,forming a hexacoordinated complex with the oxygen atoms of ribulose-1,5-bisphosphate(RuBP)and key residues in Rubisco,including Asp203,His294,Glu204,and Lys201.While the binding affinity and stability of the Cd^(2+)-Rubisco-RuBP complex are comparable to those of the Mg^(2+)-Rubisco-RuBP complex,Cd^(2+)markedly shifts the catalytic activity of Rubisco from carboxylation to oxygenation.This shift results in the accumulation of 2-phosphoglycolate(2-PG),a photorespiration byproduct,by up to 11.57-fold.Consequently,the enhanced photorespiration pathway increases CO_(2) release,leading to a significant reduction in net CO_(2) fixation and ultimately inhibiting rice growth under hydroponic conditions.By elucidating the molecular mechanism through which Cd disrupts Rubisco’s dual catalytic activity,this study advances our understanding of how heavy metals impair carbon metabolism and carbon sequestration in plants,offering critical insights for mitigating Cd-induced carbon sink losses in cropland.展开更多
Although open-central canopy(OCC)is popular in apple(Malus×domestica)orchards in Loess Plateau of China,its relevant photosynthetic mechanisms have not been elucidated.In this study,changes in photosynthetically ...Although open-central canopy(OCC)is popular in apple(Malus×domestica)orchards in Loess Plateau of China,its relevant photosynthetic mechanisms have not been elucidated.In this study,changes in photosynthetically active radiation(PAR),gas exchange,chlorophyll fluorescence quenching and fruit quality in apple trees were measured in OCC and compared with those in the conventional condensed round and large canopy(RLC).Results showed that light intercepted at different orientations was 44%higher by OCC than that by RLC.The improved light environment within OCC remarkably increased leaf maximum net photosynthetic rate(Pnmax)and significantly decreased stomatal limitation.Under high light,the ratio of photorespiratory rate to gross photosynthetic rate(Pr/Pg)in OCC was higher than that in RLC.Moreover,reversible component in non-photochemical quenching(r(qE))was increased,while irreversible component(r(qI))was decreased in OCC than in RLC.As a result,the fruit quality in OCC was greatly boosted as evidenced by the significantly increased single fruit weight,fruit flesh firmness and fruit soluble solid contents and the sharply decreased fruit titratable acid contents.PAR intercepted by the canopy and the fruit soluble solid contents,leaf Pnmaxor single fruit weight were positively correlated,while PAR or Pnmaxwas negatively correlated with the fruit titratable acid contents.Accordingly,the improved crown light environment and the enhanced leaf photosynthetic performance and photoprotective capacity in OCC led to the boosted fruit quality.展开更多
Climate change is resulting in more frequent and rapidly changing temperatures at both extremes that severely affect the growth and production of plants,particularly crops.Oxidative stress caused by high temperatures ...Climate change is resulting in more frequent and rapidly changing temperatures at both extremes that severely affect the growth and production of plants,particularly crops.Oxidative stress caused by high temperatures is one of the most damaging factors for plants.However,the role of hydrogen peroxide(H_(2)O_(2))in modulating plant thermotolerance is largely unknown,and the regulation of photorespiration essential for C3 species remains to be fully clarified.Here,we report that heat stress promotes H2O2 accumulation in chloroplasts and that H2O2 stimulates sulfenylation of the chloroplast-localized photorespiratory enzyme 2-phosphoglycolate phosphatase 1(PGLP1)at cysteine 86,inhibiting its activity and promoting the accumulation of the toxic metabolite 2-phosphoglycolate.We also demonstrate that PGLP1 has a positive function in plant thermotolerance,as PGLP1 antisense lines have greater heat sensitivity and PGLP1-overexpressing plants have higher heat-stress tolerance than the wild type.Together,our results demonstrate that heat-induced H2O2 in chloroplasts sulfenylates and inhibits PGLP1 to modulate plant thermotolerance.Furthermore,targeting CATALASE2 to chloroplasts can largely prevent the heatinduced overaccumulation of H2O2 and the sulfenylation of PGLP1,thus conferring thermotolerance without a plant growth penalty.These findings reveal that heat-induced H2O2 in chloroplasts is important for heat-caused plant damage.展开更多
Hydrogen peroxide （H2O2） operates as a signaling molecule in eukaryotes, but the specificity of its signal- ing capacities remains largely unrevealed. Here, we analyzed whether a moderate production of H2O2 from two...Hydrogen peroxide （H2O2） operates as a signaling molecule in eukaryotes, but the specificity of its signal- ing capacities remains largely unrevealed. Here, we analyzed whether a moderate production of H2O2 from two different plant cellular compartments has divergent effects on the plant transcriptome. Arabidopsis thaliana overexpressing glycolate oxidase in the chloroplast （Fahnenstich et al., 2008; Balazadeh et al., 2012） and plants deficient in peroxisomal catalase （Queval et al., 2007; Inze et al., 2012） were grown under non-photorespiratory conditions and then transferred to photorespiratory conditions to foster the production of H202 in both organelles. We show that H202 originating in a specific organelle induces two types of responses： one that integrates signals independently from the subcellular site of H202 production and another that is dependent on the H2O2 production site. H2O2 produced in peroxisomes induces transcripts involved in protein repair responses, while H2O2 produced in chloroplasts induces early signaling responses, including transcription factors and biosynthetic genes involved in production of secondary signaling messengers. There is a significant bias towards the induction of genes involved in responses to wounding and pathogen attack by chloroplas- tic-produced H202, including indolic glucosinolates-, camalexin-, and stigmasterol-biosynthetic genes. These transcriptional responses were accompanied by the accumulation of 4-methoxy-indol-3-ylmethyl glucosinolate and stigmasterol.展开更多
The mechanism by which the mitochondrial alternative oxidase （AOX） pathway contributes to photosystem II （PSII） photoprotection is in dispute. It was generally thought that the AOX pathway protects photosystems by...The mechanism by which the mitochondrial alternative oxidase （AOX） pathway contributes to photosystem II （PSII） photoprotection is in dispute. It was generally thought that the AOX pathway protects photosystems by dissipating excess reducing equivalents exported from chloroplasts through the malate/oxaloacetate （Mal/OAA） shuttle and thus preventing the over-reduction of chloroplasts. In this study, using the aoxla Arabidopsis mutant and nine other C3 and C4 plant species, we revealed an additional action model of the AOX pathway in PSII photoprotection. Although the AOX pathway contributes to PSII photoprotection in C3 leaves treated with high light, this contribution was observed to disappear when photorespiration was suppressed. Disruption or inhibition of the AOX pathway significantly decreased the photorespiration in C3 leaves. Moreover, the AOX pathway did not respond to high light and contributed little to PSII photoprotection in C4 leaves possessing a highly active Mal/OAA shuttle but with little photorespiration. These results demonstrate that the AOX pathway contributes to PSII photoprotection in C3 plants by maintaining photo- respiration to detoxify glycolate and via the indirect export of excess reducing equivalents from chloro-plasts by the MaI/OAA shuttle. This new action model explains why the AOX pathway does not contribute to PSII photoprotection in C4 plants.展开更多
During the last ice age, CO2 concentration （[CO2]） was 180-200 umol/mol compared with the modern value of 380 umol/mol, and global temperatures were -8 ℃ cooler. Relatively little is known about the responses of C3...During the last ice age, CO2 concentration （[CO2]） was 180-200 umol/mol compared with the modern value of 380 umol/mol, and global temperatures were -8 ℃ cooler. Relatively little is known about the responses of C3 and C4 species to longterm exposure to glacial conditions. Here Abutilon theophrasti Medik. （C3） and Amaranthus retroflexus L. （C4） were grown at 200 umol/mol CO2 with current （30/24℃） and glacial （22/16℃） temperatures for 22d. Overall, the C4 species exhibited a large growth advantage over the C3 species at low [CO2]. However, this advantage was reduced at low temperature, where the C4 species produced 5x the total mass of the C3 species versus 14x at the high temperature. This difference was due to a reduction in C4 growth at low temperature, since the C3 species exhibited similar growth between temperatures. Physiological differences between temperatures were not detected for either species, although photorespiration/net photosynthesis was reduced in the C3 species grown at low temperature, suggesting evidence of improved carbon balance at this treatment. This system suggests that C4 species had a growth advantage over C3 species during low [CO2] of the last ice age, although concurrent reductions in temperatures may have reduced this advantage.展开更多
Plant respiration is characterized by two pathways for electron transfer to O2, namely the cytochrome pathway （CP） that is linked to ATP production, and the alternative pathway （AP）, where electrons from ubiquinol...Plant respiration is characterized by two pathways for electron transfer to O2, namely the cytochrome pathway （CP） that is linked to ATP production, and the alternative pathway （AP）, where electrons from ubiquinol are directly transferred to O2 via an alternative oxidase （AOX） without concomitant ATP production. This latter pathway is well suited to dispose of excess electrons in the light, leading to optimized photosynthetic performance. We have characterized T- DNA-insertion mutant lines of Arabidopsis thaliana that do not express the major isoform, AOXIA. In standard growth conditions, these plants did not show any phenotype, but restriction of electron flow through CP by antimycin A, which induces AOXIA expression in the wild-type, led to an increased expression of AOXID in leaves of the aoxla-knockout mutant. Despite the increased presence of the AOX1D isoform in the mutant, antimycin A caused inhibition of photosyn- thesis, increased ROS, and ultimately resulted in amplified membrane leakage and necrosis when compared to the wild- type, which was only marginally affected by the inhibitor. It thus appears that AOX1 D was unable to fully compensate for the loss of AOXIA when electron flow via the CP is restricted. A combination of inhibition studies, coupled to metabolite profiling and targeted expression analysis of the P-protein of glycine decarboxylase complex （GDC）, suggests that the aoxla mutants attempt to increase their capacity for photorespiration. However, given their deficiency, it is intriguing that increase in expression neither of AOX1D nor of GDC could fully compensate for the lack of AOXIA to optimize pho- tosynthesis when treated with antimycin A. We suggest that the aoxla mutants can further be used to substantiate the current models concerning the influence of mitochondrial redox on photosynthetic performance and gene expression.展开更多
Mutations in the photorespiration pathway dis- play a lethal phenotype in atmospheric air, which can be fully recovered by elevated C02. An exception is that mutants of peroxisomal hydroxypyruvate reductase （HPR1） d...Mutations in the photorespiration pathway dis- play a lethal phenotype in atmospheric air, which can be fully recovered by elevated C02. An exception is that mutants of peroxisomal hydroxypyruvate reductase （HPR1） do not have this phenotype, indicating the presence of cytosolic bypass in the photorespiration pathway. In this study, we constructed overexpression of the OsHPR1 gene and RNA interference plants of OsHPR1 and OsHPR2 genes in rice （Oryza sativo L. cv. Zhonghua 11）. Results from reverse transcription-polymerase chain reaction （RT-PCR）, Western blot, and enzyme assays showed that HPR1 activity changed significantly in corresponding transgenic lines without any effect on HPR2 activity, which is the same for HPR2. However, metabolite analysis and the serine glyoxylate aminotransferase （SGAT） activity assay showed that the metabolite flux of photorespiration was disturbed in RNAi lines of both HPR genes. Furthermore, HPR1 and HPR2 proteins were located to the peroxisome and cytosol, respectively, by transient expression experiment. Double mutant hprl x hpr2 was generated by crossing individual mutant of hprl and hpr2. The phenotypes of all transgenic lines were determined in ambient air and C02-elevated air. The phenotype typical of photorespiration mutants was observed only where activity of both HPRI and HPR2 were downregulated in the same line. These findings demonstrate that two hydroxypyruvate reductases encoded by OsHPRI and OsHPR2 are involved in photorespiratory metabolism in rice.展开更多
Photosynthesis in crops and natural vegetation allows light energy to be converted into chemical energy and thus forms the foundation for almost all terrestrial trophic networks on Earth.The efficiency of photosynthet...Photosynthesis in crops and natural vegetation allows light energy to be converted into chemical energy and thus forms the foundation for almost all terrestrial trophic networks on Earth.The efficiency of photosynthetic energy conversion plays a crucial role in determining the portion of incident solar radiation that can be used to generate plant biomass throughout a growth season.Consequently,alongside the factors such as resource availability,crop management,crop selection,maintenance costs,and intrinsic yield potential,photosynthetic energy use efficiency significantly influences crop yield.Photosynthetic efficiency is relevant to sustainability and food security because it affects water use efficiency,nutrient use efficiency,and land use efficiency.This review focuses specifically on the potential for improvements in photosynthetic efficiency to drive a sustainable increase in crop yields.We discuss bypassing photorespiration,enhancing light use efficiency,harnessing natural variation in photosynthetic parameters for breeding purposes,and adopting new-to-nature approaches that show promise for achieving unprecedented gains in photosynthetic efficiency.展开更多
Transgenic tomato （Solanum lycopersicum） plants were generated expressing a fragment of the mitochon- drial NAD-dependent isocitrate dehydrogenase gene （SIIDH1） in the antisense orientation. The transgenic plants ...Transgenic tomato （Solanum lycopersicum） plants were generated expressing a fragment of the mitochon- drial NAD-dependent isocitrate dehydrogenase gene （SIIDH1） in the antisense orientation. The transgenic plants displayed a mild reduction in the activity of the target enzyme in the leaves but essentially no visible alteration in growth from the wild-type. Fruit size and yield were, however, reduced. These plants were characterized by relatively few changes in pho- tosynthetic parameters, but they displayed a minor decrease in maximum photosynthetic efficiency （Fv/Fm）. Furthermore, a clear reduction in flux through the tricarboxylic acid （TCA） cycle was observed in the transformants. Additionally, bio- chemical analyses revealed that the transgenic lines exhibited considerably altered metabolism, being characterized by slight decreases in the levels of amino acids, intermediates of the TCA cycle, photosynthetic pigments, starch, and NAD（P）H levels, but increased levels of nitrate and protein. Results from these studies show that even small changes in mitochon- drial NAD-dependent isocitrate dehydrogenase activity lead to noticeable alterations in nitrate assimilation and suggest the presence of different strategies by which metabolism is reprogrammed to compensate for this deficiency.展开更多
Although a considerable increase in our knowledge concerning the importance of metabolic adjustments to unfavorable growth conditions has been recently provided, relatively little is known about the adjustments which ...Although a considerable increase in our knowledge concerning the importance of metabolic adjustments to unfavorable growth conditions has been recently provided, relatively little is known about the adjustments which occur in response to fluctuation in environmental factors. Evaluating the metabolic adjustments occurring under changing environmental conditions thus offers a good opportunity to increase our current understanding of the crosstalk between the major pathways which are affected by such conditions. To this end, plants growing under normal conditions were transferred to different light and temperature conditions which were anticipated to affect （amongst other processes） the rates of photosynthesis and photorespiration and characterized at the physiological, molecular, and metabolic levels following this transition. Our results revealed similar behavior in response to both treatments and imply a tight connec- tivity of photorespiration with the major pathways of plant metabolism. They further highlight that the majority of the regulation of these pathways is not mediated at the level of transcription but that leaf metabolism is rather pre-poised to adapt to changes in these input parameters.展开更多
基金Dalian Science and Technology Innovation Project(2019J13SN120).
文摘[Objectives]This study was conducted to investigate the effects of compound photorespiration inhibitors on related indexes of sweet cherry.[Methods]With the main sweet cherry variety‘Meizao’as a test material,relevant research work was carried out.[Results]Several compound photorespiration inhibitors had a better promotion effect on the photosynthetic capacity,yield and quality of sweet cherry variety‘Meizao’,and especially,the combination of 300 mg/L sodium bicarbonate,300 mg/L sodium bisulfite,300 mg/L 2,3-epoxypropionic acid and 1.5%tween-80 had the best effect.[Conclusions]The combined use of the three photorespiration inhibitors is better than the single use,and produces a good synergistic effect.
基金Project supported by the National Basic Research Program of China (No.2005CB121101)National Natural Science Foundation of China (Nos.30400279 and 30671233)International Foundation for Science (IFS)(No.C/3799-1)
文摘Under high light conditions, ammonium nutrition has a negative effect on plant growth. This suggests that the adverse effects of ammonium nutrition on plant growth may be related to carbon gain, photosynthesis, and photorespiration. However, there is no consistent evidence of a specific mechanism that could explain the plant growth reduction under ammonium supply. It is generally accepted that during the light reaction, a surplus of nicotinamide adenine dinucleotide hydrogen phosphate （NADPH） is produced, which is not completely used during the assimilation of CO2, Nitrate reduc- tion in the leaf represents an additional sink for NADPH that is not available to ammonium-grown plants. Nitrate and ammonium nutrition may use different pathways for NADPH consumption, which leads to differences in photosynthesis and photorespiration. The morphological （i.e., cell size, mesophyll thickness, and chloroplast volume） and enzymic （i.e., ribulose-1,5-bisphosphate carboxylase/oxygenase （Rubisco）, phosphoenolpyruvate carboxylase （PEPCase）, and glutamine synthetase/glutamate synthetase （GS/GOGAT）） differences that develop when plants are treated with either nitrate or ammonium nitrogen forms are related to photosynthesis and photorespiration. The differences in photorespiration rate for plants treated with nitrate or ammonium are related to the conversion of citrate to 2-oxoglutarate （2-OG） and photorespiratory CO2 refixation.
文摘Photosynthetic rate (Pn) and the partitioning of noncyclic photosynthetic electron transport to photorespiration (Jo) in seedlings of four subtropical woody plants growing at three light intensities were studied in the summer time by measurements of chlorophyll fluorescence and CO2 exchange. Except Schima superba, an upper canopy tree species, the tree species Castanopsis fissa and two understory shrubs Psychotria rubra, Ardisia quinquegona had the highest Pn at 36% of sunlight intensity. The total photosynthetic electron transport rate (JF) and the ratio of Jo/JF were elevated in leaves under full sunlight. Jo/JF ratio reached 0.5-0.6 and coincided with the increasing of oxygenation rate of Rubisco (Vo), the activity of glycolate oxidase and photorespiration rate at full sunlight. It is suggested that an increasing partitioning proportion of photosynthetic electron transport to photorespiration might be one of the protective regulation mechanisms in forest plant under strong summer light and high temperature conditions.
基金supported by the research grant OPP1172157 Realizing Increased Photosynthetic Efficiency (RIPE) that is funded by the Bill & Melinda Gates Foundation, Foundation for Food and Agriculture Research, and the UK Department for International Development
文摘In C3 plants, photorespiration is an energyexpensive process, including the oxygenation of ribulose-1,5-bisphosphate(RuBP) by ribulose 1,5-bisphosphate carboxylase/oxygenase(Rubisco) and the ensuing multiorganellar photorespiratory pathway required to recycle the toxic byproducts and recapture a portion of the fixed carbon. Photorespiration significantly impacts crop productivity through reducing yields in C3 crops by as much as 50%under severe conditions. Thus, reducing the flux through, or weive R improving the efficiency of photorespiration has the potential of large improvements in C3 crop productivity.Here, we review an array of approaches intended to engineer photorespiration in a range of plant systems with the goal of increasing crop productivity. Approaches include optimizing flux through the native photorespiratory pathway, installing non-native alternative photorespiratory pathways, and lowering or even eliminating Rubiscocatalyzed oxygenation of RuBP to reduce substrate entrance into the photorespiratory cycle. Some proposed designs have been successful at the proof of concept level.A plant systems-engineering approach, based on new opportunities available from synthetic biology to implement in silico designs, holds promise for further progress toward delivering more productive crops to farmer’s fields.
基金Project supported by the National Natural Science Foundation of China.
文摘Photorespiration is a well-known CO<sub>2</sub>-evolution process accompanying photosyntheticCO<sub>2</sub> uptake, whereas its physiological significance is still not well understood. As alreadyreported, severe photoinhibition occurred in the leaves or chloroplasts exposed to stronglight in the absence of CO<sub>2</sub> upon suppression of photorespiration, while photoinhibitioncould be prevented by the supply of CO<sub>2</sub> at a concentration near the compensation point.
文摘The photorespiratory pathway or photorespiration is an essential process in oxygenic photosynthetic or- ganisms, which can reduce the efficiency of photosynthetic carbon assimilation and is hence frequently considered as a wasteful process. By comparing the response of the wild-type plants and mutants impaired in photorespiration to a shift in ambient C02 concentrations, we demonstrate that photorespiration also plays a beneficial role during short-term acclimation to reduced C02 availability. The wild-type plants re- sponded with few differentially expressed genes, mostly involved in drought stress, which is likely a conse- quence of enhanced opening of stomata and concomitant water loss upon a shift toward low C02. In contrast, mutants with impaired activity of photorespiratory enzymes were highly stressed and not able to adjust stomatal conductance to reduced external C02 availability. The transcriptional response of mutant plants was congruent, indicating a general reprogramming to deal with the consequences of reduced C02 availability, signaled by enhanced oxygenation of ribulose-l,5-bisphosphate and amplified by the artificially impaired photorespiratory metabolism. Central in this reprogramming was the pro- nounced reallocation of resources from growth processes to stress responses. Taken together, our results indicate that unrestricted photorespiratory metabolism is a prerequisite for rapid physiological acclimation to a reduction in C02 availability.
基金supported by the National Natural Science Foundation of China (31671594)Guangdong Basic and Applied Basic Research Foundation (2024A1515011098,2021A1515012482).
文摘The involvement of the endoplasmic reticulum(ER)-localized adenylate transporter1(ER-ANT1)in photorespiratory metabolism has been established,yet its precise physiological function remains uncertain.Rice er-ant1 mutant plants grown in ambient air exhibited stunted growth and substantial alterations in amino acid metabolites,but recovery in a high CO_(2) condition(1.5%).We show that the absence of ERANT1 hindered the breakdown of glycine without affecting its synthesis,leading to a substantial accumulation of glycine,diminished levels of serine,and depleted reserves of glutamate and alanine.Intriguingly,the er-ant1 plants grown in high CO_(2) and later exposed to ambient air displayed reduced serine levels within 12 h,yet they accumulated serine a week after transferring to ambient air due to induced phosphorylated serine synthesis pathways.Furthermore,knockout of ER-ANT1 marginally impacted the transcription of genes governing core enzymes in photorespiration,but notably upregulated BOU expression that encodes a putative mitochondrial glutamate transporter and AGAT1 that encodes an alanine:glyoxylate aminotransferase gene.Surprisingly,AGAT1,an ER-localized protein,exhibited higher activity that correlates with the decreased alanine levels observed in the er-ant1 mutant.Lack of ER-ANT1 activity also led to a significantly elevated NADH/NAD+ratio that potentially hinders the glycine-to-serine conversion process.This supports the hypothesis that the lack of ER-ANT1-induced limitation of ATP usage might inhibit GDC activity by modulating the NADH/NAD+ratio.Moreover,non-proteinogenic amino acids,including β-alanine and γ-aminobutyrate(GABA),underwent significant alterations,even under high CO_(2) conditions in the er-ant mutant,implying additional non-photorespiration roles of ER-ANT1.Taken together,our results indicate that ER-localized ER-ANT1 plays a crucial role in amino acid metabolism during photorespiration.
文摘In midday ginkgo ( Ginkgo biloba L.) leaves have to bear photon flux density over 1400 μmol·m -2 ·s -1 in combination with high temperatures around 35 ℃ at natural habitat. They show typical midday depression of stomatal conductance and of CO 2 assimilation rate. The zeaxanthin changes with light intensity during the day. The influence of the combination of strong light and temperature on photoinhibition was also examined in the laboratory. A low CO 2 internal conductance (31 mmol·m -2 ·s -1 ) was found in ginkgo leaves, which had been exposed to excessive light at temperature between 15 ℃ and 35 ℃ with reduced CO 2 (80 μL·L -1 ) or oxygen (2%) for 2 h, causing a low CO 2 concentration at the carboxylation site and a high proportion of photorespiration. The ratio of electron transport to CO 2 fixation was rather high in ginkgo (16 e -/CO 2 at 25 ℃) as compared with other plants. It increased with temperature also in 2% O 2 which could not be explained solely as due to change of photorespiration. The reduction of oxygen in 340 or 80 μL·L -1 CO 2 had no effect on the extent of photoinhibition at all temperatures, which indicated that electron flow caused by photorespiration in excess light was negligible in protective effect in ginkgo leaves. However, a decreased CO 2 concentration increased photoinhibition, especially at high temperature. It is concluded that the dissipation of excessive excitation energy in the PSⅡ antennae through the xanthophyll cycle may be the major protective mechanism to preventing from the deteriorated effects of strong light in ginkgo leaves.
文摘The peculiarities of leaf carbon dioxide gas exchange in soybean genotypes grown in field over a large area and contrasting in duration of vegetation, photosynthetic traits and productivity were studied. Varietal differences in the daily and ontogenetic changes in photosynthesis and photorespiration were identified. It was established that the period of the high activity of photosynthetic apparatus in high productive soybean genotypes lasts for a longer time. The photosynthetic rate and the rate of CO2 release in light due to photorespiration are higher in high productive genotypes. A value of photorespiration in contrasting soybean genotypes constitutes about 28% - 35% of photosynthetic rate. The ratio of gross photosynthesis to photorespiration in genotypes with different productivity is constant enough during ontogenesis, indicating a direct positive correlation between gross photosynthesis and photorespiration. Therefore, contrary to conception arisen during many years on the waste-fulness of photorespiration, taking into account the versatile investigations on different aspects of photo-respiration, it was proved that photorespiration is one of the evolutionarily developed vital metabolic processes in plants and the attempts to reduce this process with the purpose of increasing the crop productivity are inconsistent.
基金supported by the National Natural Science Foundation of China(Nos.22436006 and 22306158).
文摘Cadmium(Cd)contamination poses a significant threat to the carbon fixation potential of farmland ecosystems,yet the molecular mechanisms underlying its inhibitory effects remain poorly understood.This study reveals that Cd competitively binds to ribulose-1,5-bisphosphate carboxylase/oxygenase(Rubisco),the key enzyme in photosynthetic carbon fixation,by displacing its native co-factor,magnesium(Mg).Both Cd^(2+)and Mg^(2+)bind to identical sites on Rubisco,forming a hexacoordinated complex with the oxygen atoms of ribulose-1,5-bisphosphate(RuBP)and key residues in Rubisco,including Asp203,His294,Glu204,and Lys201.While the binding affinity and stability of the Cd^(2+)-Rubisco-RuBP complex are comparable to those of the Mg^(2+)-Rubisco-RuBP complex,Cd^(2+)markedly shifts the catalytic activity of Rubisco from carboxylation to oxygenation.This shift results in the accumulation of 2-phosphoglycolate(2-PG),a photorespiration byproduct,by up to 11.57-fold.Consequently,the enhanced photorespiration pathway increases CO_(2) release,leading to a significant reduction in net CO_(2) fixation and ultimately inhibiting rice growth under hydroponic conditions.By elucidating the molecular mechanism through which Cd disrupts Rubisco’s dual catalytic activity,this study advances our understanding of how heavy metals impair carbon metabolism and carbon sequestration in plants,offering critical insights for mitigating Cd-induced carbon sink losses in cropland.
基金supported by Chinese National Key R&D Program(Grant No.2016YFD0201118)Shanxi Province Key R&D Program(Grant No.201903D211001-24-1)+2 种基金Agricultural Sci-Tech Innovation Project Program of Shanxi Academy of Agricultural Sciences(Grant No.YGC2019TD08-2)Agricultural Sci-Tech Innovation Research Program of Shanxi Academy of Agricultural Sciences(Grant Nos.YCX2020402,YCX2020302)Prior Support Program of Shanxi Academy of Agricultural Sciences(Grant No.YCX2018D2YS04)。
文摘Although open-central canopy(OCC)is popular in apple(Malus×domestica)orchards in Loess Plateau of China,its relevant photosynthetic mechanisms have not been elucidated.In this study,changes in photosynthetically active radiation(PAR),gas exchange,chlorophyll fluorescence quenching and fruit quality in apple trees were measured in OCC and compared with those in the conventional condensed round and large canopy(RLC).Results showed that light intercepted at different orientations was 44%higher by OCC than that by RLC.The improved light environment within OCC remarkably increased leaf maximum net photosynthetic rate(Pnmax)and significantly decreased stomatal limitation.Under high light,the ratio of photorespiratory rate to gross photosynthetic rate(Pr/Pg)in OCC was higher than that in RLC.Moreover,reversible component in non-photochemical quenching(r(qE))was increased,while irreversible component(r(qI))was decreased in OCC than in RLC.As a result,the fruit quality in OCC was greatly boosted as evidenced by the significantly increased single fruit weight,fruit flesh firmness and fruit soluble solid contents and the sharply decreased fruit titratable acid contents.PAR intercepted by the canopy and the fruit soluble solid contents,leaf Pnmaxor single fruit weight were positively correlated,while PAR or Pnmaxwas negatively correlated with the fruit titratable acid contents.Accordingly,the improved crown light environment and the enhanced leaf photosynthetic performance and photoprotective capacity in OCC led to the boosted fruit quality.
基金supported by grants from the National Key Research and Development Program of China(2022YFD1200400)the National Natural Science Foundation of China(32301864 and 32322010).
文摘Climate change is resulting in more frequent and rapidly changing temperatures at both extremes that severely affect the growth and production of plants,particularly crops.Oxidative stress caused by high temperatures is one of the most damaging factors for plants.However,the role of hydrogen peroxide(H_(2)O_(2))in modulating plant thermotolerance is largely unknown,and the regulation of photorespiration essential for C3 species remains to be fully clarified.Here,we report that heat stress promotes H2O2 accumulation in chloroplasts and that H2O2 stimulates sulfenylation of the chloroplast-localized photorespiratory enzyme 2-phosphoglycolate phosphatase 1(PGLP1)at cysteine 86,inhibiting its activity and promoting the accumulation of the toxic metabolite 2-phosphoglycolate.We also demonstrate that PGLP1 has a positive function in plant thermotolerance,as PGLP1 antisense lines have greater heat sensitivity and PGLP1-overexpressing plants have higher heat-stress tolerance than the wild type.Together,our results demonstrate that heat-induced H2O2 in chloroplasts sulfenylates and inhibits PGLP1 to modulate plant thermotolerance.Furthermore,targeting CATALASE2 to chloroplasts can largely prevent the heatinduced overaccumulation of H2O2 and the sulfenylation of PGLP1,thus conferring thermotolerance without a plant growth penalty.These findings reveal that heat-induced H2O2 in chloroplasts is important for heat-caused plant damage.
文摘Hydrogen peroxide （H2O2） operates as a signaling molecule in eukaryotes, but the specificity of its signal- ing capacities remains largely unrevealed. Here, we analyzed whether a moderate production of H2O2 from two different plant cellular compartments has divergent effects on the plant transcriptome. Arabidopsis thaliana overexpressing glycolate oxidase in the chloroplast （Fahnenstich et al., 2008; Balazadeh et al., 2012） and plants deficient in peroxisomal catalase （Queval et al., 2007; Inze et al., 2012） were grown under non-photorespiratory conditions and then transferred to photorespiratory conditions to foster the production of H202 in both organelles. We show that H202 originating in a specific organelle induces two types of responses： one that integrates signals independently from the subcellular site of H202 production and another that is dependent on the H2O2 production site. H2O2 produced in peroxisomes induces transcripts involved in protein repair responses, while H2O2 produced in chloroplasts induces early signaling responses, including transcription factors and biosynthetic genes involved in production of secondary signaling messengers. There is a significant bias towards the induction of genes involved in responses to wounding and pathogen attack by chloroplas- tic-produced H202, including indolic glucosinolates-, camalexin-, and stigmasterol-biosynthetic genes. These transcriptional responses were accompanied by the accumulation of 4-methoxy-indol-3-ylmethyl glucosinolate and stigmasterol.
文摘The mechanism by which the mitochondrial alternative oxidase （AOX） pathway contributes to photosystem II （PSII） photoprotection is in dispute. It was generally thought that the AOX pathway protects photosystems by dissipating excess reducing equivalents exported from chloroplasts through the malate/oxaloacetate （Mal/OAA） shuttle and thus preventing the over-reduction of chloroplasts. In this study, using the aoxla Arabidopsis mutant and nine other C3 and C4 plant species, we revealed an additional action model of the AOX pathway in PSII photoprotection. Although the AOX pathway contributes to PSII photoprotection in C3 leaves treated with high light, this contribution was observed to disappear when photorespiration was suppressed. Disruption or inhibition of the AOX pathway significantly decreased the photorespiration in C3 leaves. Moreover, the AOX pathway did not respond to high light and contributed little to PSII photoprotection in C4 leaves possessing a highly active Mal/OAA shuttle but with little photorespiration. These results demonstrate that the AOX pathway contributes to PSII photoprotection in C3 plants by maintaining photo- respiration to detoxify glycolate and via the indirect export of excess reducing equivalents from chloro-plasts by the MaI/OAA shuttle. This new action model explains why the AOX pathway does not contribute to PSII photoprotection in C4 plants.
基金Supported by the US Department of Energy (DE-FG02-95ER62124)the US National Science Foundation (0517668 and 0746822)an American Fellowship to JK Ward from the American Association of University Women Educational Foundation.
文摘During the last ice age, CO2 concentration （[CO2]） was 180-200 umol/mol compared with the modern value of 380 umol/mol, and global temperatures were -8 ℃ cooler. Relatively little is known about the responses of C3 and C4 species to longterm exposure to glacial conditions. Here Abutilon theophrasti Medik. （C3） and Amaranthus retroflexus L. （C4） were grown at 200 umol/mol CO2 with current （30/24℃） and glacial （22/16℃） temperatures for 22d. Overall, the C4 species exhibited a large growth advantage over the C3 species at low [CO2]. However, this advantage was reduced at low temperature, where the C4 species produced 5x the total mass of the C3 species versus 14x at the high temperature. This difference was due to a reduction in C4 growth at low temperature, since the C3 species exhibited similar growth between temperatures. Physiological differences between temperatures were not detected for either species, although photorespiration/net photosynthesis was reduced in the C3 species grown at low temperature, suggesting evidence of improved carbon balance at this treatment. This system suggests that C4 species had a growth advantage over C3 species during low [CO2] of the last ice age, although concurrent reductions in temperatures may have reduced this advantage.
文摘Plant respiration is characterized by two pathways for electron transfer to O2, namely the cytochrome pathway （CP） that is linked to ATP production, and the alternative pathway （AP）, where electrons from ubiquinol are directly transferred to O2 via an alternative oxidase （AOX） without concomitant ATP production. This latter pathway is well suited to dispose of excess electrons in the light, leading to optimized photosynthetic performance. We have characterized T- DNA-insertion mutant lines of Arabidopsis thaliana that do not express the major isoform, AOXIA. In standard growth conditions, these plants did not show any phenotype, but restriction of electron flow through CP by antimycin A, which induces AOXIA expression in the wild-type, led to an increased expression of AOXID in leaves of the aoxla-knockout mutant. Despite the increased presence of the AOX1D isoform in the mutant, antimycin A caused inhibition of photosyn- thesis, increased ROS, and ultimately resulted in amplified membrane leakage and necrosis when compared to the wild- type, which was only marginally affected by the inhibitor. It thus appears that AOX1 D was unable to fully compensate for the loss of AOXIA when electron flow via the CP is restricted. A combination of inhibition studies, coupled to metabolite profiling and targeted expression analysis of the P-protein of glycine decarboxylase complex （GDC）, suggests that the aoxla mutants attempt to increase their capacity for photorespiration. However, given their deficiency, it is intriguing that increase in expression neither of AOX1D nor of GDC could fully compensate for the lack of AOXIA to optimize pho- tosynthesis when treated with antimycin A. We suggest that the aoxla mutants can further be used to substantiate the current models concerning the influence of mitochondrial redox on photosynthetic performance and gene expression.
基金supported by the National Natural Science Foundation of China (U1201212 31170222)+1 种基金the Shenzhen Overseas Talents Innovation and Entrepreneurship Funding Scheme (The Peacock Scheme)China Postdoctoral Science Foundation (2013M530374)
文摘Mutations in the photorespiration pathway dis- play a lethal phenotype in atmospheric air, which can be fully recovered by elevated C02. An exception is that mutants of peroxisomal hydroxypyruvate reductase （HPR1） do not have this phenotype, indicating the presence of cytosolic bypass in the photorespiration pathway. In this study, we constructed overexpression of the OsHPR1 gene and RNA interference plants of OsHPR1 and OsHPR2 genes in rice （Oryza sativo L. cv. Zhonghua 11）. Results from reverse transcription-polymerase chain reaction （RT-PCR）, Western blot, and enzyme assays showed that HPR1 activity changed significantly in corresponding transgenic lines without any effect on HPR2 activity, which is the same for HPR2. However, metabolite analysis and the serine glyoxylate aminotransferase （SGAT） activity assay showed that the metabolite flux of photorespiration was disturbed in RNAi lines of both HPR genes. Furthermore, HPR1 and HPR2 proteins were located to the peroxisome and cytosol, respectively, by transient expression experiment. Double mutant hprl x hpr2 was generated by crossing individual mutant of hprl and hpr2. The phenotypes of all transgenic lines were determined in ambient air and C02-elevated air. The phenotype typical of photorespiration mutants was observed only where activity of both HPRI and HPR2 were downregulated in the same line. These findings demonstrate that two hydroxypyruvate reductases encoded by OsHPRI and OsHPR2 are involved in photorespiratory metabolism in rice.
基金funding by the European Union H2020 Program(project GAIN4CROPS,GA no.862087,to B.S.,G.F.,G.C,D.T.,T.M.,T.J.E.,A.P.M.W.,M.H.,E.N.S.,O.E.,J.M.H.,and T.T.)the Deutsche Forschungsgemeinschaft(Cluster of Excellence for Plant Sciences[CEPLAS]under Germany’s Excellence Strategy EXC-2048/1 under project ID 390686111 to B.S.,O.E.,and A.P.M.W.and CRC TRR 341“Plant Ecological Genetics”to B.S.and A.P.M.W.).
文摘Photosynthesis in crops and natural vegetation allows light energy to be converted into chemical energy and thus forms the foundation for almost all terrestrial trophic networks on Earth.The efficiency of photosynthetic energy conversion plays a crucial role in determining the portion of incident solar radiation that can be used to generate plant biomass throughout a growth season.Consequently,alongside the factors such as resource availability,crop management,crop selection,maintenance costs,and intrinsic yield potential,photosynthetic energy use efficiency significantly influences crop yield.Photosynthetic efficiency is relevant to sustainability and food security because it affects water use efficiency,nutrient use efficiency,and land use efficiency.This review focuses specifically on the potential for improvements in photosynthetic efficiency to drive a sustainable increase in crop yields.We discuss bypassing photorespiration,enhancing light use efficiency,harnessing natural variation in photosynthetic parameters for breeding purposes,and adopting new-to-nature approaches that show promise for achieving unprecedented gains in photosynthetic efficiency.
文摘Transgenic tomato （Solanum lycopersicum） plants were generated expressing a fragment of the mitochon- drial NAD-dependent isocitrate dehydrogenase gene （SIIDH1） in the antisense orientation. The transgenic plants displayed a mild reduction in the activity of the target enzyme in the leaves but essentially no visible alteration in growth from the wild-type. Fruit size and yield were, however, reduced. These plants were characterized by relatively few changes in pho- tosynthetic parameters, but they displayed a minor decrease in maximum photosynthetic efficiency （Fv/Fm）. Furthermore, a clear reduction in flux through the tricarboxylic acid （TCA） cycle was observed in the transformants. Additionally, bio- chemical analyses revealed that the transgenic lines exhibited considerably altered metabolism, being characterized by slight decreases in the levels of amino acids, intermediates of the TCA cycle, photosynthetic pigments, starch, and NAD（P）H levels, but increased levels of nitrate and protein. Results from these studies show that even small changes in mitochon- drial NAD-dependent isocitrate dehydrogenase activity lead to noticeable alterations in nitrate assimilation and suggest the presence of different strategies by which metabolism is reprogrammed to compensate for this deficiency.
文摘Although a considerable increase in our knowledge concerning the importance of metabolic adjustments to unfavorable growth conditions has been recently provided, relatively little is known about the adjustments which occur in response to fluctuation in environmental factors. Evaluating the metabolic adjustments occurring under changing environmental conditions thus offers a good opportunity to increase our current understanding of the crosstalk between the major pathways which are affected by such conditions. To this end, plants growing under normal conditions were transferred to different light and temperature conditions which were anticipated to affect （amongst other processes） the rates of photosynthesis and photorespiration and characterized at the physiological, molecular, and metabolic levels following this transition. Our results revealed similar behavior in response to both treatments and imply a tight connec- tivity of photorespiration with the major pathways of plant metabolism. They further highlight that the majority of the regulation of these pathways is not mediated at the level of transcription but that leaf metabolism is rather pre-poised to adapt to changes in these input parameters.
