After incubation at 42℃ for more than 48 h, brown damages occurred on the stems of tobacco (Nicotiana tabacum L.) ndhC-ndhK-ndhJ deletion mutant (?ndhCKJ), followed by wilt of the leaves, while less the phenotype was...After incubation at 42℃ for more than 48 h, brown damages occurred on the stems of tobacco (Nicotiana tabacum L.) ndhC-ndhK-ndhJ deletion mutant (?ndhCKJ), followed by wilt of the leaves, while less the phenotype was found in its wild type (WT). Analysis of the kinetics of post-illumination rise in chlorophyll fluorescence indicated that the PSI cyclic electron flow and the chlororespiration mediated by NAD(P)H dehydrogenase (NDH) was significantly enhanced in WT under the high temperature. After leaf disks were treated with methyl viologen (MV), photosynthetic apparatus of ?ndhCKJ exhibited more severe photo-oxidative damage, even bleaching of chlorophyll. Analysis of P700 oxidation and reduction showed that the NDH mediated cyclic electron flow probably functioned as an electron competitor with Mehler reaction, to reduce the accumulation of reactive oxygen species (ROS). When leaf disks were heat stressed at 42℃ for 6 h, the photochemical activity declined more markedly in ?ndhCKJ than in WT, accompanied with more evident decrease in the amount of soluble Rubisco activase. In addition, the slow phase of millisecond-delayed light emission (ms-DLE) of chlorophyll fluorescence indicated that NDH was involved in the building-up of transthy-lakoid proton gradient (?pH), while the consumption of ?pH was highly inhibited in ?ndhCKJ after heat stress. Based on the results, we supposed that the cyclic electron flow mediated by NDH could be stimulated under the heat stressed conditions, to divert excess electrons via chlororespiration pathway, and sustain CO2 assimilation by providing extra ?pH, thus reducing the photooxidative damage.展开更多
Plants often encounter light intensities exceeding the capacity of photosynthesis(excessive light)mainly due to biotic and abiotic factors,which lower C02 fixation and reduce light energy sinks.Under excessive light,t...Plants often encounter light intensities exceeding the capacity of photosynthesis(excessive light)mainly due to biotic and abiotic factors,which lower C02 fixation and reduce light energy sinks.Under excessive light,the photosynthetic electron transport chain generates damaging molecules,hence leading to photooxidative stress and eventually to cell death.In this review,we summarize the mechanisms linking the excessive absorption of light energy in chloroplasts to programmed cell death in plant leaves.We highlight the importance of reactive carbonyl species generated by lipid photooxidation,their detoxification,and the integrating role of the endoplasmic reticulum in the adoption of phototolerance or cell-death pathways.Finally,we invite the scientific community to standardize the conditions of excessive light treatments.展开更多
Selaginella lepidophylla is one of only a few species of spike mosses （Selaginellaceae） that have evolved des-iccation tolerance （DT） or the ability to ＇resurrect＇ from an air-dried state. In order to understand...Selaginella lepidophylla is one of only a few species of spike mosses （Selaginellaceae） that have evolved des-iccation tolerance （DT） or the ability to ＇resurrect＇ from an air-dried state. In order to understand the metabolic basis of DT, S, lepidophylla was subjected to a five-stage, rehydration/dehydration cycle, then analyzed using non-biased, global metabolomics profiling technology based on GC/MS and UHLC/MS/MS2 platforms. A total of 251 metabolites including 167 named （66.5%） and 84 （33.4%） unnamed compounds were characterized. Only 42 （16.7%） and 74 （29.5%） of compounds showed significantly increased or decreased abundance, respectively, indicating that most compounds were produced con-stitutively, including highly abundant trehalose, sucrose, and glucose. Several glycolysis/gluconeogenesis and tricarboxylic acid （TCA） cycle intermediates showed increased abundance at 100% relative water content （RWC） and 50% RWC. Vanillate, a potent antioxidant, was also more abundant in the hydrated state. Many different sugar alcohols and sugar acids were more abundant in the hydrated state. These polyols likely decelerate the rate of water loss during the drying process as well as slow water absorption during rehydration, stabilize proteins, and scavenge reactive oxygen species （ROS）. In contrast, nitrogen-rich and y-glutamyl amino acids, citrulline, and nucleotide catabolism products （e.g. allantoin） were more abundant in the dry states, suggesting that these compounds might play important roles in nitrogen remobilization during rehydration or in ROS scavenging. UV-protective compounds such as 3-（3-hydroxyphenyl）propionate, apigenin, and naringenin, were more abundant in the dry states. Most lipids were produced constitutively, with the exception of choline phosphate, which was more abundant in dry states and likely plays a role in membrane hydration and stabilization. In contrast, several poly- unsaturated fatty acids were more abundant in the hydrated states, suggestin展开更多
Understanding abiotic stress responses is one of the most important issues in plant research nowadays. Abiotic stress, including excess light, can promote the onset of oxidative stress through the accumulation of reac...Understanding abiotic stress responses is one of the most important issues in plant research nowadays. Abiotic stress, including excess light, can promote the onset of oxidative stress through the accumulation of reactive oxygen species. Oxidative stress also arises when in vitro propagated plants are exposed to high light upon transfer to ex vitro. To determine whether the underlying pathways activated at the transfer of in vitro grapevine to ex vitro conditions reflect the processes occurring upon light stress, we used Vitis vinifera Affymetrix GeneChip （VvGA） and a custom array of genes responsive to light stress （LSCA） detected by real-time reverse transcriptase PCR （qRT-PCR）. When gene-expression profiles were compared, ＇protein metabolism and modification＇, ＇signaling＇, and ＇anti-oxidative＂ genes were more represented in LSCA, while, in VvGA, ＇cell wall metabolism＇ and ＇secondary metabolism＇ were the categories in which gene expression varied more significantly. The above functional categories confirm previous studies involving other types of abiotic stresses, enhancing the common attributes of abiotic stress defense pathways. The LSCA analysis of our experimental system detected strong response of heat shock genes, particularly the protein rescuing mechanism involving the cooperation of two ATP-dependent chaperone systems, Hsp100 and Hsp70, which showed an unusually late response during the recovery period, of extreme relevance to remove non-functional, potentially harmful polypeptides arising from misfolding, denaturation, or aggregation brought about by stress. The success of LSCA also proves the feasibility of a custommade qRT-PCR approach, particularly for species for which no GeneChip is available and for researchers dealing with a specific and focused problem.展开更多
基金supported in part by the National Natural Science Foundation of China(Grant Nos.30270123&90306013).
文摘After incubation at 42℃ for more than 48 h, brown damages occurred on the stems of tobacco (Nicotiana tabacum L.) ndhC-ndhK-ndhJ deletion mutant (?ndhCKJ), followed by wilt of the leaves, while less the phenotype was found in its wild type (WT). Analysis of the kinetics of post-illumination rise in chlorophyll fluorescence indicated that the PSI cyclic electron flow and the chlororespiration mediated by NAD(P)H dehydrogenase (NDH) was significantly enhanced in WT under the high temperature. After leaf disks were treated with methyl viologen (MV), photosynthetic apparatus of ?ndhCKJ exhibited more severe photo-oxidative damage, even bleaching of chlorophyll. Analysis of P700 oxidation and reduction showed that the NDH mediated cyclic electron flow probably functioned as an electron competitor with Mehler reaction, to reduce the accumulation of reactive oxygen species (ROS). When leaf disks were heat stressed at 42℃ for 6 h, the photochemical activity declined more markedly in ?ndhCKJ than in WT, accompanied with more evident decrease in the amount of soluble Rubisco activase. In addition, the slow phase of millisecond-delayed light emission (ms-DLE) of chlorophyll fluorescence indicated that NDH was involved in the building-up of transthy-lakoid proton gradient (?pH), while the consumption of ?pH was highly inhibited in ?ndhCKJ after heat stress. Based on the results, we supposed that the cyclic electron flow mediated by NDH could be stimulated under the heat stressed conditions, to divert excess electrons via chlororespiration pathway, and sustain CO2 assimilation by providing extra ?pH, thus reducing the photooxidative damage.
基金the French National Research Agency(ANR project SLOSAM,14-CE02-0010-02).
文摘Plants often encounter light intensities exceeding the capacity of photosynthesis(excessive light)mainly due to biotic and abiotic factors,which lower C02 fixation and reduce light energy sinks.Under excessive light,the photosynthetic electron transport chain generates damaging molecules,hence leading to photooxidative stress and eventually to cell death.In this review,we summarize the mechanisms linking the excessive absorption of light energy in chloroplasts to programmed cell death in plant leaves.We highlight the importance of reactive carbonyl species generated by lipid photooxidation,their detoxification,and the integrating role of the endoplasmic reticulum in the adoption of phototolerance or cell-death pathways.Finally,we invite the scientific community to standardize the conditions of excessive light treatments.
文摘Selaginella lepidophylla is one of only a few species of spike mosses （Selaginellaceae） that have evolved des-iccation tolerance （DT） or the ability to ＇resurrect＇ from an air-dried state. In order to understand the metabolic basis of DT, S, lepidophylla was subjected to a five-stage, rehydration/dehydration cycle, then analyzed using non-biased, global metabolomics profiling technology based on GC/MS and UHLC/MS/MS2 platforms. A total of 251 metabolites including 167 named （66.5%） and 84 （33.4%） unnamed compounds were characterized. Only 42 （16.7%） and 74 （29.5%） of compounds showed significantly increased or decreased abundance, respectively, indicating that most compounds were produced con-stitutively, including highly abundant trehalose, sucrose, and glucose. Several glycolysis/gluconeogenesis and tricarboxylic acid （TCA） cycle intermediates showed increased abundance at 100% relative water content （RWC） and 50% RWC. Vanillate, a potent antioxidant, was also more abundant in the hydrated state. Many different sugar alcohols and sugar acids were more abundant in the hydrated state. These polyols likely decelerate the rate of water loss during the drying process as well as slow water absorption during rehydration, stabilize proteins, and scavenge reactive oxygen species （ROS）. In contrast, nitrogen-rich and y-glutamyl amino acids, citrulline, and nucleotide catabolism products （e.g. allantoin） were more abundant in the dry states, suggesting that these compounds might play important roles in nitrogen remobilization during rehydration or in ROS scavenging. UV-protective compounds such as 3-（3-hydroxyphenyl）propionate, apigenin, and naringenin, were more abundant in the dry states. Most lipids were produced constitutively, with the exception of choline phosphate, which was more abundant in dry states and likely plays a role in membrane hydration and stabilization. In contrast, several poly- unsaturated fatty acids were more abundant in the hydrated states, suggestin
文摘Understanding abiotic stress responses is one of the most important issues in plant research nowadays. Abiotic stress, including excess light, can promote the onset of oxidative stress through the accumulation of reactive oxygen species. Oxidative stress also arises when in vitro propagated plants are exposed to high light upon transfer to ex vitro. To determine whether the underlying pathways activated at the transfer of in vitro grapevine to ex vitro conditions reflect the processes occurring upon light stress, we used Vitis vinifera Affymetrix GeneChip （VvGA） and a custom array of genes responsive to light stress （LSCA） detected by real-time reverse transcriptase PCR （qRT-PCR）. When gene-expression profiles were compared, ＇protein metabolism and modification＇, ＇signaling＇, and ＇anti-oxidative＂ genes were more represented in LSCA, while, in VvGA, ＇cell wall metabolism＇ and ＇secondary metabolism＇ were the categories in which gene expression varied more significantly. The above functional categories confirm previous studies involving other types of abiotic stresses, enhancing the common attributes of abiotic stress defense pathways. The LSCA analysis of our experimental system detected strong response of heat shock genes, particularly the protein rescuing mechanism involving the cooperation of two ATP-dependent chaperone systems, Hsp100 and Hsp70, which showed an unusually late response during the recovery period, of extreme relevance to remove non-functional, potentially harmful polypeptides arising from misfolding, denaturation, or aggregation brought about by stress. The success of LSCA also proves the feasibility of a custommade qRT-PCR approach, particularly for species for which no GeneChip is available and for researchers dealing with a specific and focused problem.
