Molecular Mechanism of Damage and Repair Processes in Photosynthesis

本研究项目的重点是光合成组织对压力的反应的分子机制的简化，以提高光、活性氧物质和高温度的高强度。以下是一些主要成就的例子。（1）Synechocystis psbA 2基因的体外随机突变体sp.PCC6803通过PCR，在320 muE·m^<-2>·s^<-1>提供了18个不同的突变体，以抑制光强度的高，同时也包括颜料和生长率的条件。根据所分析的D1蛋白质上的特异性氨基酸（s）的替代物的特异性氨基酸（s）的分子机理，所述分子机理被吸收到这些突变体中。（2） Transgenic tobacco plants enriched or reduced in plastidic glutamine synthetase （GS2）， a key enzyme in photorespiration， were constructed。这些转基因植物有两次GS 2的正常产量，并增加了对照片泄漏的能力，增加了对高inte的容忍度 ... More 在亮度光的情况下，如果它们用一个减少的GS 2的数量来减少光的发射能力，并且由于光的强度与控制植物比较而被抑制了更多的光。从这些结果中，它被合并为摄影抑制的C_3植物。（3）转基因烟草植物具有两种增强活性的谷氨酰胺还原酶（GR）和超氧化物歧化酶（SOD）在两种转基因线之间产生交叉-介质;大肠杆菌中有一种GR基因，另一种有一种cDNA用于细胞氧化Cu/Zn SOD的cDNA。三种类型的转基因植物，我，GR植物用2.5把较高的GR活性放进去， SOD植物用2.8把较高的SOD活性放进去， GR-SOD植物用2.8和1.4把较高的GR和SOD活性放进去，因此，比对照植物更多，用paraquat处理。GR-SOD转基因植物的叶子显示出更高的耐受性，不仅仅是控制植物，但也不仅仅是GR-SOD转基因植物。这些观察证实，由于这种研究依赖于paraquat对光氧化压力的容忍性导致了对光氧化压力的依赖，而这两个酶体正在一起工作以保护植物对抗氧化压力。Less（低）

This research project was focus on the elucidation of molecular mechanism of stress-responses of photosynthetic organisms to wards high intensity of light, active oxygen species and high temperatures. Followings are some examples of major achievements.(1) In vitro random mutagenesis of psbA2 gene of Synechocystis sp.PCC 6803 by PCR with a low fidelity of amplification and subsequent screening at 320 muE・m^<-2>・s^<-1> have provided us 18 distinct mutants tolerant to the high intensity of light, both in terms of pigmentation and growth rate. The molecular mechanisms by which the photo-tolerance has been acquired in these mutants by the substitution of specific amino acid (s) on D1 protein were analyzed.(2) Transgenic tobacco plants enriched or reduced in plastidic glutamine synthetase (GS2), a key enzyme in photorespiration, were constructed. Those transgenic plants having twice the normal amount of GS2 had an improved capacity for photorespiration and an increased tolerance to high-inte … More nsity light, whereas those with a reduced amount of GS2 had a diminished capacity for photorespiration and were photoinhibited more severely by high-intensity of light compared with control plants. From these results, it is concluded that photorespiration protects C_3 plants from photoinhibition.(3) Transgenic tobacco plants with enhanced activities of both glutathione reductase (GR) and superoxide dismutase (SOD) were generated by cross-fertilization between two transgenic lines ; one which had a GR gene from E.coli and another which had a cDNA for cytosolic Cu/Zn SOD from Oryza sativa. Three types of transgenic plants, i.e., GR plants with 2.5-fold higher GR activity, SOD plants with 2.8-fold higher SOD activity, GR-SOD plants with 2.8- and 1.4-fold higher activities of GR and SOD,respectively, than those of control plants, were treated with paraquat. Leaves of the GR-SOD transgenic plants exhibited higher tolerance to paraquat not only more than the control plants but also more than the GR- and the SOD-transgenic plants. These observations confirm that the tolerance of leaves to photooxidative stress caused by paraquat in this study depended on cytosolic activities of both GR and SOD,and that these two enzymes are working together to protect plants against oxidative stress. Less