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Molecular Mechanism of Damage and Repair Processes in Photosynthesis

光合作用损伤与修复过程的分子机制

基本信息

批准号：
04273101
负责人：
SATOH Kimiyuki
金额：
$ 138.5万
依托单位：
Okayama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research on Priority Areas
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1995
项目状态：
已结题

项目摘要

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

该研究项目的重点是阐明光合生物对高强度光、活性氧和高温胁迫反应的分子机制。主要成果如下：(1)通过PCR对集胞藻PCC 6803 psbA2基因进行体外随机诱变，低保真扩增，并在320 muE·m^<-2>·s^<-1>下进行筛选，获得了18个在色素沉着和生长速度方面均能耐受高强度光的不同突变体。分析了这些突变体通过D1蛋白上特定氨基酸的取代而获得光耐受性的分子机制。(2)构建了光呼吸关键酶质体谷氨酰胺合成酶(GS2)富集或减少的转基因烟草植株。与对照植物相比，GS2含量为正常含量两倍的转基因植物的光呼吸能力有所提高，对高强度光的耐受性也有所提高，而GS2含量减少的转基因植物的光呼吸能力下降，并且受到高强度光的光抑制更严重。从这些结果可以得出结论，光呼吸保护C_3植物免受光抑制。(3)通过两个转基因品系之间的异花受精，获得了谷胱甘肽还原酶(GR)和超氧化物歧化酶(SOD)活性增强的转基因烟草植株。一种具有来自大肠杆菌的 GR 基因，另一种具有来自稻的胞质 Cu/Zn SOD 的 cDNA。用百草枯处理三种类型的转基因植物，即GR活性比对照植物高2.5倍的GR植物、SOD活性高2.8倍的SOD植物、GR和SOD活性分别比对照植物高2.8倍和1.4倍的GR-SOD植物。 GR-SOD转基因植物的叶子表现出更高的对百草枯的耐受性，不仅高于对照植物，而且高于GR-和SOD-转基因植物。这些观察结果证实，本研究中叶片对百草枯引起的光氧化应激的耐受性取决于GR和SOD的胞质活性，并且这两种酶共同作用以保护植物免受氧化应激。较少的