PPR蛋白家族是真核生物所特有的，并且在陆生植物中非常庞大。目前，在拟南芥中已发现多于450个PPR蛋白，水稻中多于430个。大约3/4的PPR蛋白定位在质体与线粒体中，参与质体及线粒体中的RNA代谢，在转录后水平参与基因的表达调控。目前，只有少数PPR蛋白的生物学功能被揭示。最近我们对Os02g0110400的研究发现，它可以编码一个含有11个PPR基序的PPR蛋白，将其命名为OsPPR2-1，定位于细胞质，参与水稻花粉发育。本研究通过细胞学分析，揭示RNAi植株中花粉败育的细胞学特征和败育时期；通过RNA免疫共沉淀分析，确定OsPPR2-1作用的目标RNA；利用OsPPR2-1与RNA互作实验，确定OsPPR2-1与目标RNA作用方式。最终利用这些数据阐明OsPPR2-1参与花粉发育的调控机理。

The pentatricopeptide repeat (PPR) protein Family is a eukaryote-speci?c protein family and is particularly large in land plants, with >450 members in Arabidopsis and >430 members in rice. Almost three-quarters of PPR proteins are predicted to be targeted to either mitochondria or chloroplasts and play crucial functions in their RNA metabolism, Such as RNA cleavage, processing, splicing, RNA editing, and translational activation. The PPR proteins are characterized by the presence of tandem arrays of a degenerate 35 amino acid repeat，the PPR motif，repeated in tandem 2-26 times. Bio-chemical structures indicate that PPR protein may combine RNAs and proteins. At present, only a few of PPR proteins have been revealed their biological functions. Recently, we focus on Os02g0110400 , which can express a PPR protein containing 11 PPR motifs, and have found that it may be a cytoplasmic PPR protein and has a significant role in male gametogenesis . Through cytological analysis, We will uncover the cytological characteristics and abortive period of RNAi plants; Through RNA immunoprecipitation we will find the target RNAs of OsPPR2-1; Through the interaction between OsPPR2-1 and target RNAs in vitro, we can confirm the mode of action between them. Our results will uncover the mechanism in which OsPPR2-1 regulates pollen development.

PPR蛋白家族是真核生物特有的，并且在陆生植物中大量存在。目前，在拟南芥中发现450多个PPR基因，水稻中也多于430个。大约3/4的PPR蛋白定位在质体或者线粒体中，参与质体或者线粒体中的RNA代谢，在转录后水平调控基因的表达。目前，还没有细胞质定位的PPR基因的功能被揭示。本项目中研究的PPR基因OsPPR2-1，在花粉发育的小孢子早期与小孢子晚期表达量最高，并且在小孢子内部以及绒毡层中都有表达。蛋白不定位于线粒体和叶绿体，而是定位在细胞质中。通过反义、RNAi、Crisper-Cas9技术使其表达下调，都可以导致花粉育性下降和结实率下降，异交授粉表明，OsPPR2-1的表达下降只是导致花粉败育。细胞学分析表明，OsPPR2-1的表达下降后，花粉母细胞减数分裂正常，败育花粉停留在单核阶段，绒毡层中质体明显增加，PCD和降解过程明显推迟。RNA免疫共沉淀和转录组分析表明，OsPPR2-1是mRNA结合蛋白，其表达下降，导致小孢子发育过程中减数分裂相关基因以及绒毡层中质体发育相关基因不能及时降解。我们选择了两个OsPPR2-1结合的靶基因进行了研究，这两个基因也是绒毡层的降解和PCD的关键基因。也上结果说明，OsPPR2-1通过调控减数分裂相关基因以及绒毡层中质体发育相关基因的mRNA适时降解，控制绒毡层中质体发育和花粉能够顺利从减数分裂进入有丝分裂。以上说明，通过我们的研究发现了一条花粉发育的新途径。