叶绿体内膜蛋白FtsHi1参与叶绿体基因组维持及基因表达调控的分子机制

作为半自主细胞器，叶绿体具有独立的基因组。叶绿体基因组与大量蛋白形成拟核结构。在叶绿体发育的早期，拟核与叶绿体内被膜紧密结合，随着叶绿体的发育，拟核逐渐从内膜上分离下来。但叶绿体DNA的复制以及修复等过程都是发生在拟核结合在内被膜状态时发生的，暗示着内膜系统在叶绿体基因组维持以及基因表达中具有重要作用，但是相关的分子机制一直不清楚。我们前期的研究发现叶绿体内膜蛋白FtsHi1在叶绿体基因组拷贝数调控中具有重要作用，而且它和叶绿体转录调控因子DG1之间存在遗传互作关系。基于以上发现，本研究将综合运用遗传学、生物化学以及植物生理学等技术手段，系统深入研究FtsHi1蛋白参与叶绿体基因组复制/稳定性调控的分子机制，揭示FtsHi1与DG1在参与叶绿体基因表达调控过程中的功能关系。该项目研究将有助于深入了解叶绿体转录复合物和DNA复制复合物的分子关系以及叶绿体基因组和和核基因组之间的协同机制。

As a semi-autonomous organelle derived from a cyanobacterial ancestor, the chloroplast of higher plant contains its own genomes. Within chloroplasts, multiple copies of plastid DNA together with a great number of proteins are organized in structures that are similar to bacterial nucleoids. The composition shaping and organization of plastid nucleoids are dynamically changed during chloroplast development. In the proplastids and development plastids, nucleoids are attached to the inner envelop whereas in mature chloroplasts the nucleoids are attached to the thylakoid membrane. It is generally accepted that the activities maintaining DNA number and integrity take place on the DNA firmly associated with membrane-attached nucleoids, suggesting that components of inner envelop membranes control the maintenance and/or expression of plastid genome DNA. However, the underlying mechanism still remains elusive. Our primary study showed that an inner envelope protein FtsHi1 is involved in the regulation of the copy number of plastid DNA and genetically interacted with a transcription regulator DG1. Based on these findings, we will explore the mechanism of FtsHi1 involved in plastid DNA replication and/or genome stability via the combination of the genetic and biochemical approaches. We will also study the relationship between DG1 and FtsHi1 in the regulation of plastid gene expression. This study will uncover the mechanical connection and functional interplay between plastid DNA replication and transcription complexes and put insights into the coordination mechanism between the nuclear and plastid genetic systems.