拟南芥生长素合成基因YUC2调控叶绿体RNA编辑的机理研究

Chloroplast RNA editing is a post-transcriptional process that converts cytidine to uridine at specific sites within RNA molecules, which depends on multiple nuclear-encoded editing factors. RNA editing plays important roles in maintaining normal function of chloroplasts and regulating plant disease resistance and fruit quality. In previous studies, we have found that loss-of-function mutation in auxin biosynthesis-related gene YUC2 resulted in decreased RNA editing rate, while exogenous IAA application increased RNA editing rate. These results indicate that close relations exist between auxin and chloroplast RNA editing, while the specific regulatory mechanism and physiological function are still not clear. In this project, we will further determine whether chloroplast RNA editing is directly regulated by auxin through auxin content determination and inhibitor treatment. Meanwhile, the editing factors that might be regulated by auxin will be identified and verified by gene expression analysis. Then, genetic and biochemical experiments will be performed to reveal the relationship between auxin response factors (ARFs) and the RNA editing factors. Therefore, the auxin signaling pathway that regulates chloroplast RNA editing will be illuminated. In addition, we will study the relationship between auxin signal-regulated RNA editing and chloroplast development and photosynthetic efficiency. It is expected that the results of this project will help to reveal the mechanism and biological significance of auxin in regulating chloroplast RNA editing.

叶绿体RNA编辑是一种转录后加工方式，将RNA上特定位点的胞嘧啶转换为尿嘧啶，该过程依赖于很多核基因编码的编辑因子。RNA编辑在维持叶绿体功能、调节植物抗病及果实品质等方面具有重要作用。我们前期发现拟南芥生长素合成基因YUC2缺失显著抑制叶绿体RNA编辑，而施加外源IAA则明显促进编辑。结果初步建立了生长素与叶绿体RNA编辑的联系，但具体调控机制及生物学意义不清楚。本项目以yuc2突变体作为切入点，进一步通过生长素含量测定及抑制剂处理等手段确定叶绿体RNA编辑是否受生长素直接调控，同时通过基因表达分析鉴定可能受生长素调控的编辑因子并加以验证，再结合遗传和生化实验分析生长素信号下游响应因子ARFs与编辑因子的关系，进而揭示调控叶绿体RNA编辑的生长素信号通路。另外我们还将研究生长素调控RNA编辑与叶绿体发育及光合效率的关系。本研究有望揭示生长素调控叶绿体RNA编辑的机理及生物学意义。

叶绿体RNA编辑是一种重要的基因转录后加工方式，主要是将前体RNA上特定位点的胞嘧啶转换为尿嘧啶从而改变遗传信息，其过程发生依赖于PPR等编辑因子。RNA编辑被报道在植物胚胎发育、营养生长以及抗逆等方面发挥着重要作用。生长素是最早被发现的植物激素，广泛参与植物生长发育的各个阶段，但目前为止没有报道生长素与叶绿体RNA编辑之间是否存在调控关系。本项目中我们通过对生长素合成缺陷突变体yuc2进行分析，发现了生长素能够调控叶绿体RNA编辑过程，并且鉴定了多个受其调控的编辑位点。通过转录组分析等进一步发现很多已报道的PPR编码基因在yuc2突变体中都有一定程度的下调，且生信分析发现这些PPR基因启动子区域都存在生长素的响应元件，表明生长素可能通过调控PPR基因的表达来影响叶绿体RNA编辑过程。我们深入研究发现生长素信号下游响应因子ARF1参与生长素对叶绿体RNA编辑过程的调控。首先，ARF1功能缺失同样影响叶绿体RNA编辑位点的编辑效率及其对应的编辑因子表达。其次，我们发现ARF1能够结合到CRR4等编辑因子基因的启动子区域调控其表达。本项目我们还揭示了生长素调控的叶绿体accD基因的RNA编辑参与植物高温胁迫响应的分子机制。这些发现拓展了对植物叶绿体RNA编辑内在调控机制及其在植物逆境响应过程中的重要作用的认识。