Molecular Mechanisms for Responses of Photosynthetic organisms to Environments

研究目的：本研究的目的是；（一）分离与光合生物适应各种环境条件有关的基因；(2)利用分离得到的基因改造高等植物和蓝藻；(3)通过分析转化植株的表型来阐明环境驯化的分子机制。主要研究成果：(1)低温驯化与耐受性：从蓝藻中分离到几个参与光合生物低温驯化的脂肪酸去饱和酶基因。对插入抗生素基因盒灭活这些基因的突变体的分析表明，膜脂脂肪酸的不饱和通过加速D1蛋白的生物发生来保护光系统II复合体免受光抑制。(2)耐盐性：从土壤细菌中分离到合成甘糖碱的ch…More oline氧化酶的codA基因，该基因与光合生物对盐胁迫的适应和耐受有关。带codA基因的蓝藻和拟南芥的转化通过保护光系统II复合体免受光抑制状态而增强了对盐胁迫的耐受性。(3) CO_2富集机理；当蓝藻细胞暴露在低CO_2条件下时，它们会积极积累CO_2。我们分离到了一个细胞内浓缩CO_2能力缺陷的突变体，并通过互补分离到了一个细胞内浓缩CO_2能力缺陷的基因。(4)对无机离子缺乏的适应：我们分离了一个磷酸盐缺乏传感器的基因和一个转录因子的基因，该基因在传感器的控制下磷酸化。(5)干旱诱导基因表达：rd29A是拟南芥干旱诱导基因之一。系统缺失对该基因上游区域的影响表明，该基因有两个顺式区域；一种直接受干旱调节，另一种通过脱落酸的合成来调节。少

Purpose of Research : The purpose of this research was ; (1) to isolate genes which are involved in the acclimation of photosynthetic organisms to varieties of environmental conditions ; (2) to transform higher plants and cyanobacteria with the isolated genes ; and (3) to elucidate the molecular mechanisms of the acclimation to the environment by analyzing the phenotypes of transformed plants.Main Results of Research : (1) Acclimation and tolerance to low temperature : we isolated, from cyanobacteria, several genes for fatty acid desaturases which are involved in the acclimation of photosynthetic organisms to low temperature. Analysis of mutants in which these genes were inactivated by insertion of antibiotic gene cartridges, indicated that the unsaturation of fatty acids of membrane lipids protected the photosystem II complex against photoinhibition by accelerating the biogenesis of the D1 protein. (2) Tolerance to salt stress : we isolated, from a soil bacterium, the codA gene for ch … More oline oxidase that synthesizes glycinebetaine which is involved in the acclimation to and tolerance of photosynthetic organisms to the salt stress. The transformation of cyanobacteria and Arabidopsis thaliana with the codA gene enhanced the tolerance to salt stress by protection of the photosystem II complex from the photoinhibited state. (3) Mechanisms of concentration of CO_2 ; cyanobacterial cells actively accumulate CO_2 when they are exposed to low-CO_2 conditions. We isolated a mutant which was defective in the ability ot intracellularly concentrate CO_2 and isolated a gene for the ability by complementation. (4) Acclimation to deficiency of inorganic ions : We isolated a gene for a sensor of deficiency of phosphate and a gene for a transcription factor which was phosphorylated under control of the sensor. (5) Drought-induced gene expression : One of the drought-induced genes in Arabidopsis thaliana is rd29A.Effects of systematic deletions of the upstream region of this gene indicated that there are two cis-regions ; one is regulated directly by drought and the other via synthesis of abscisic acid. Less