Functional analysis of plastid transcription factors by chloroplast transformation.

已知的质体起源于原核生物的光合作用蓝藻。因此，叶绿体是半自主的，包含它们自己的遗传系统。在高等植物中，叶绿体含有一个小的原核型基因组，编码120个基因。高等植物体内含有两种类型的RNA聚合酶，即真细菌类型的PEP和噬菌体类型的NEP。为了识别启动子，PEP需要一个可交换的亚基--西格玛因子。在细菌中，各种西格玛因子特异性地识别不同的启动子序列。高等植物也编码多个西格玛因子基因。叶绿体Sigma因子是叶绿体基因表达和叶绿体分化的关键调节因子。这项研究揭示了叶绿体分化和环境反应中的叶绿体西格玛因子的作用。首先，我们揭示了SIG6是叶绿体中一个早期的一般西格玛因子，在幼苗发育的早期阶段对叶绿体的发育起着关键作用。此外，我们还证明了SIG5在叶绿体中作为一种特殊的SIGMA因子，选择性地识别PSBD LRP以响应各种环境胁迫。

Plastids are known to have originated from prokaryotic photosynthetic cyanobacteria. Consequently plastids are semi-autonomous and contain their own genetic system. In higher plants, plastids contain a small prokaryotic-type genome which encodes _120 genes. Higher plant plastids contain two types of RNA polymerases, eubacterial-type PEP (plastid-encoded plastid RNA polymerase) and phage-type NEP (nuclearencoded plastid RNA polymerase). In order to recognize promoters, PEP requires an exchangeable subunit, sigma factor. In bacteria, a variety of sigma factors specifically recognize different promoter sequences. Higher plants also encode multiple sigma factor genes. Chloroplast sigma factors are key regulators of the chloroplast gene expression and chloroplast differentiation. This research revealed the roles of plastid sigma factors in chloroplast differentiation and environmental responses. Firstly, we have revealed that SIG6 is an early general sigma factor in plastids that plays a key role in chloroplast development at an early stage of seedling development. Furthermore, we demonstrated that SIG5 acts as a special sigma factor in chloroplasts that selectively recognizes the psbD LRP in response to various environmental stresses.