Functional analysis of plastid transcription factors by chloroplast transformation.

众所周知，质体起源于原核光合作用的蓝藻。因此，质体是半自主的，包含自己的遗传系统。在高等植物中，质体包含一个小的原核型基因组，可编码_120个基因。高等植物质体包含两种类型的RNA聚合酶，真菌体型PEP（质体编码的质体RNA聚合酶）和噬菌体型NEP（核编码的质体RNA聚合酶）。为了识别启动子，PEP需要一个可交换的亚基，sigma因子。在细菌中，多种sigma因子特异性识别不同的启动子序列。高等植物也编码多个sigma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控因子。本研究揭示了质体sigma因子在叶绿体分化和环境响应中的作用。首先，我们发现SIG6是质体中一个早期的通用sigma因子，在幼苗发育早期叶绿体发育中起关键作用。此外，我们证明了SIG5在叶绿体中作为一种特殊的sigma因子，在各种环境胁迫下选择性地识别psbD LRP。

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.