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Modulation of chlorophyll synthesis and its effect on the biogenesis of two photosystems

叶绿素合成的调节及其对两个光系统生物发生的影响

基本信息

批准号：
08836006
负责人：
FUJITA Yuichi
金额：
$ 1.54万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

项目摘要

1. Physiological roles of the two protochlorophyllide reduction systemsCyanobacteria have two protochlorophyllide (Pchlide) reductases catalyzing the conversion of Pchlide to chlorophyllide, a key step in the biosynthetic pathway of chlorophyll (Chl) ; a light-dependent (LPOR) and a light-independent (DPOR) reductase. Gene (por) encoding LPOR has been cloned from Plectonema boryanum, and a por-disrupted mutant, YFP12, was isolated by target mutagenesis to compare phenotype of YFP12 with those of wild-type and a chlL-disrupted (DPOR-less) mutant, YFC2. YFP12 grew as well as wild type under low light conditions, but not under high light conditions (>130 mu E m^<-2>s^<-1>). In contrast, YFC2 was able to grow under both light conditions. These results suggested that, although both the reductases contributed to Chl synthesis in the cells growing in the light, LPOR was essential for the cells to grow under the high light intensity.2. Analysis of the construction of the photosystems under a limitation of Chl availability.YFC2 lacking DPOR was etiolated to reduce the Chl content less than 0.5% of the original level when this mutant was continued to grow under dark for a number of generations. Under this etiolating process, we analyzed the construction of two photosystems, PSI and PSII.Polypeptides of PSII,CP43 and 33 kDa subunit were contained at the level comparable to wild type, while those of PSI,PsaA/PsaB and PsaC were reduced an undetectable level by western analysis. This results suggested that the limitation of Chl supply resulted in the preferential degradation of PSI.

1.两种原叶绿素还原系统的生理作用蓝细菌具有两种原叶绿素（Pchlide）还原酶，催化Pchlide转化为叶绿素（Chl）的生物合成途径中的关键步骤;光依赖性（LPOR）和光非依赖性（DPOR）还原酶。已克隆了来自伯氏刺毛藻的编码LPOR的基因（por），并通过靶向诱变分离了por破坏的突变体YFP 12，以比较YFP 12与野生型和chIL破坏（DPOR-少）突变体YFC 2的表型。YFP 12在弱光条件下生长得和野生型一样好，但在强光条件下（>130 μ E·m·<-2>s·<-1>）则不然。相比之下，YFC 2能够在两种光照条件下生长。这些结果表明，虽然两种还原酶都参与了光下生长的细胞中叶绿素的合成，但LPOR是细胞在强光下生长所必需的.叶绿素有效性限制条件下的光系统结构分析DPOR缺失突变体YFC 2在黑暗条件下连续生长数代后，叶绿素含量下降到原始水平的0.5%以下。在此黄化过程中，我们分析了两个光系统PSI和PSII的结构，通过Western分析，PSII、CP 43和33 kDa亚基的多肽含量与野生型相当，而PSI、PsaA/PsaB和PsaC的多肽含量降低到检测不到的水平。这一结果表明，叶绿素供应的限制导致优先降解PSI。