The role of chloroplast NAD(P)H dehydrogenase in protection of tobacco plant against heat stress  

作　　者：WANG Peng YE Jiyu SHEN Yungang MI Hualing 

机构地区：[1]National Laboratory of Plant Molecular Genetics, Institute of Plant Physiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China National Laboratory of Plant Molecular Genetics, Institute of Plant Physiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China National Laboratory of Plant Molecular Genetics, Institute of Plant Physiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China National Laboratory of Plant Molecular Genetics, Institute of Plant Physiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China

出　　处：《Science China(Life Sciences)》2006年第4期311-321,共11页中国科学（生命科学英文版）

基　　金：supported in part by the National Natural Science Foundation of China(Grant Nos.30270123&90306013).

摘　　要：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.After incubation at 42°C for more than 48 h, brown damages occurred on the stems of tobacco (Nicotiana tabacum L.) ndhC-ndhK-ndhJ deletion mutant (ΔndhCKJ), 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; 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 ΔndhCKJ exhibited more severe photo-oxidative damage, even bleaching of chlorophyll. Analysis of P700 oxidation; 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°C for 6 h, the photochemical activity declined more markedly in ΔndhCKJ 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 transthylakoid proton gradient (ΔpH), while the consumption of ΔpH was highly inhibited in ΔndhCKJ 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,; sustain CO2 assimilation by providing extra ΔpH, thus reducing the photooxidative damage.

关 键 词：NAD(P)H dehydrogenase  high temperature  photooxidative stress  CYCLIC electron transport. 

分 类 号：N[自然科学总论]