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Analysis of the preiotropic effects of a nucleus-encoded σ factor during chloroplast development

叶绿体发育过程中核编码 σ 因子的前变性效应分析

基本信息

批准号：
13640641
负责人：
KANAMARU Kengo
金额：
$ 2.75万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

A eubacterial-type RNA polymerase (PEP) in higher plants plays crucial roles in chloroplast development. Six regulatory sigma factor genes (SIG1 to SIG6) encoded in the nuclear DNA are found in Arabidpopsis, however, the definite gene specificity of each sigma factor is still unknown. We recently identified an Arabidopsis recessive pale-green mutant sig2-1 (formerly named abc1) in which T-DNA is inserted in SIG2 (formerly named sigB ; Atlg08540). This mutant could develop almost normal etioplasts under dark conditions but barely develop the small chloroplasts with poor thylakoid membranes and stacked lamellar under light conditions. In the sig2-1 mutant, both chlorophyll and photosynthetic and photosynthesis-related proteins were remarkably reduced. However, amounts of mRNAs for these plastid-encoded proteins were not altered.Further analyzes revealed that several plastid-encoded tRNAs including trnE-UUC were drastically reduced in the mutant. The plastid-encoded tRNA-Glu is indispensable for not only protein synthesis (translation) but also tetrapyrrole (chlorophyll and heme) biogenesis. We could assign -35 like and -10 like sequences to upstream of these SIG2-dependent tRNA genes, which are conserved in Arabidopsis, tobacco, spinach, rice and maize. On the other hand, transcripts of nucleus-encoded T7 phage-type RNA polymerase (NEP)-dependent genes were steadily accumulated in this mutant. These results indicate that SIG2 plays crucial roles in chloroplast development mediated by expression of some plastid-encoded tRNAs and negative regulation of NEP.

一种真细菌型RNA聚合酶（PEP）在高等植物叶绿体发育中起着至关重要的作用。拟南芥核DNA中编码有6个调控基因SIG1 ~ SIG6，但每个sigma因子的确切基因特异性尚不清楚。我们最近发现了一个拟南芥隐性淡绿色突变体SIG2 -1（以前称为abc1），其中T-DNA插入到SIG2（以前称为sigB； Atlg08540）中。该突变体在黑暗条件下几乎可以发育正常的病变体，但在光照条件下几乎不能发育小叶绿体，类囊体膜差，片状堆积。在sig2-1突变体中，叶绿素和光合作用及光合作用相关蛋白均显著减少。然而，这些质体编码蛋白的mrna数量并没有改变。进一步分析显示，包括trnE-UUC在内的几种质体编码trna在突变体中急剧减少。质体编码的tRNA-Glu不仅在蛋白质合成（翻译）中不可或缺，而且在四氟咯（叶绿素和血红素）的生物生成中也不可或缺。我们可以将-35 like和-10 like序列分配到这些sig2依赖性tRNA基因的上游，这些基因在拟南芥、烟草、菠菜、水稻和玉米中都是保守的。另一方面，核编码的T7噬菌体型RNA聚合酶（NEP）依赖基因的转录本在该突变体中稳步积累。这些结果表明，SIG2在叶绿体发育中起着至关重要的作用，通过表达一些质体编码的trna和负调控NEP。