Non-identical contributions of two membrane-bound cpSRP components, cpFtsY and Alb3, to thylakoid biogenesis
Non-identical contributions of two membrane-bound cpSRP components, cpFtsY and Alb3, to thylakoid biogenesis
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DOI：
10.1111/j.1365-313x.2008.03659.x
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发表时间：
2008-12-01
期刊：
影响因子：
7.2
通讯作者：
Nakai, Masato
中科院分区：
文献类型：
--
作者：
Asakura, Yukari;Kikuchi, Shingo;Nakai, Masato
光收集叶绿素蛋白（LHCPs）在叶绿体类囊体膜上的插入依赖于cpsrp，需要基质成分cpSRP54和cpSRP43、膜结合的SRP受体cpFtsY和完整膜蛋白Alb3。先前的研究表明，缺乏cpSRP54和cpSRP43的拟南芥突变体叶片呈淡黄色，但具有活力，而缺乏Alb3的突变体则表现出更严重的白化表型和幼苗致死率。我们之前的研究表明，缺乏cpFtsY的玉米突变体具有淡黄绿色表型，并且幼苗致死。为了更详细地比较cpFtsY和Alb3在类囊体生物发生中的体内需求，我们分离了拟南芥cpFtsY的零突变体，并与拟南芥Alb3突变体进行了生化比较。cpftsY和alb3零突变体在缺乏蔗糖的合成培养基上幼苗致死，而在添加蔗糖的培养基上，它们能够生长到较晚的发育阶段，但大多不育。cpftsY突变株叶片发黄，LHCPs含量较野生型降低10-33%。alb3叶片呈黄白色，LHCP含量低于或等于野生型的10%。有趣的是，尽管Sec和Tat机制的积累在两种突变体中都是正常的，但Sec途径底物Cyt f在cpftsY突变体中比在alb3中更严重地下降，这可能表明cpftsY和Sec易位机制之间存在功能联系。这些结果表明，cpFtsY和Alb3对类囊体生物发生的贡献基本相似，但略有不同。
The insertion of light-harvesting chlorophyll proteins (LHCPs) into the thylakoid membrane of the chloroplast is cpSRP-dependent, and requires the stromal components cpSRP54 and cpSRP43, the membrane-bound SRP receptor cpFtsY and the integral membrane protein Alb3. Previous studies demonstrated that the Arabidopsis mutant lacking both cpSRP54 and cpSRP43 had pale yellow leaves, but was viable, whereas the mutants lacking Alb3 exhibit an albino phenotype that is more severe and seedling lethality. We previously showed that a maize mutant lacking cpFtsY had a pale yellow-green phenotype and was seedling lethal. To compare the in vivo requirements of cpFtsY and Alb3 in thylakoid biogenesis in greater detail, we isolated Arabidopsis null mutants of cpftsY, and performed biochemical comparisons with the Arabidopsis alb3 mutant. Both cpftsY and alb3 null mutants were seedling lethal on a synthetic medium lacking sucrose, whereas on a medium supplemented with sucrose, they were able to grow to later developmental stages, but were mostly infertile. cpftsY mutant plants had yellow leaves in which the levels of LHCPs were reduced to 10-33% compared with wild type. In contrast, alb3 had yellowish white leaves, and the LHCP levels were less than or equal to 10% of those of wild type. Intriguingly, whereas accumulation of the Sec and Tat machineries were normal in both mutants, the Sec pathway substrate Cyt f was more severely decreased in the cpftsY mutant than in alb3, which may indicate a functional link between cpFtsY and Sec translocation machinery. These results suggest that cpFtsY and Alb3 have essentially similar, but slightly distinct, contributions to thylakoid biogenesis.