Molecular Mechanisms for Responses of Photosynthetic organisms to Environments

研究目的：本研究的目的是：(1)分离参与光合作用生物适应各种环境条件的基因；(2)用分离的基因转化高等植物和蓝藻；(3)通过分析转化植物的表型，阐明植物适应环境的分子机制。研究的主要结果：(1)低温驯化和耐受性：我们从蓝藻中分离到几个与光合作用生物适应低温有关的脂肪酸脱氢酶基因。对这些基因通过插入抗生素基因盒而失活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：我们从土壤细菌中分离到了ch…的尾巴基因。合成甜菜碱的更多的在线氧化酶，甜菜碱参与了光合作用生物对盐胁迫的适应和耐受。将coda基因导入蓝藻和拟南芥，通过保护光系统II复合体免受光抑制，提高了植物对盐胁迫的耐受性。(3)CO_2浓度机制：蓝藻细胞在低CO_2条件下能主动积累CO_2。我们分离了一个胞内浓缩CO_2能力有缺陷的突变体，并通过互补的方式分离了一个具有这种能力的基因。(4)对无机离子缺乏的适应：我们克隆了一个磷缺乏感受器的基因和一个转录因子的基因，该转录因子在该传感器的控制下被磷酸化。(5)干旱诱导基因的表达：拟南芥的干旱诱导基因之一是rd29A。对该基因上游区进行系统缺失的研究表明，该基因有两个顺式区域：一个是受干旱直接调控的区域，另一个是通过合成脱落酸调控的区域。较少

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