叶绿体为光合作用提供了反应场所和物质基础，PPR（pentatricopeptide repeat）家族蛋白是叶绿体RNA转录及转录后加工的一类重要因子。申请人在主持并结题的国家自然基金青年项目中，首次鉴定并命名了一个P型PPR家族的重要成员PDM3，发现该因子对叶绿体内核糖体RNA剪切及PEP依赖性质体基因表达有显著影响。为此，本课题将进一步揭示PDM3在质体基因mRNA稳定性、内含子剪切、翻译起始中的功能；明确PDM3对核糖体rRNA加工、成熟、组装的作用；解析PDM3与RNA结合后的晶体结构，确立分子识别模式；筛选与PDM3互作蛋白，阐释不同因子间的协同作用机制。本课题最终将从分子、细胞、发育等水平系统研究PDM3蛋白调控叶绿体基因表达的生物学功能，揭示PDM3及互作蛋白参与叶绿体RNA成熟的分子机理，为阐明P型PPR蛋白在质体基因表达中的分子作用机制奠定基础。

Chloroplasts provide location and key functional proteins for photosynthesis, and PPR (pentatricopeptide repeat) proteins are important factors in the processing of chloroplast RNA. Based on our findings in completed National Natural Science Foundation youth project, we first identified an important member of P type PPR family and named PDM3. It was found that the PDM3 had a significant effect on the RNA maturation and PEP dependent gene expression in chloroplast. Therefore, we will further analyze exact function of PDM3 on plastid genes mRNA stability, intron splicing and translation initiation; and then reveal the recognized mode of PDM3 and its RNA targets by crystal structure analysis. Finally, we use Y2H and IP methods to screen the directed or in-directed proteins of PDM3, and clarifying the molecular mechanism of PDM3 on regulation of chloroplast gene expression. This project will clearly elucidate and reveal mechanism of PDM3 and interacted proteins involved in the maturation of chloroplast RNAs and chloroplast gene expression. Taken together, the results of this study will lay foundation for revealing the regulation mechanism of P type PPR proteins in regulation of chloroplast genes expression.