结构特异识别蛋白1（SSRP1）在百合花粉细胞分化命运中的功能研究

The mechanism of cell differentiation is one of the central issues in developmental biology. However, our understanding of the mechanism remains limited. In flower plant, pollen as highly reduced male gametophyte has been considered as an excellent model to investigate the molecular mechanisms underlying cell differentiation. Recently, we have analyzed the differentially expressed nuclear protein between vegetative nuclei (VN) and generative nuclei (GN) by quantitative proteomic method and identified one structure specific recognition protein 1 (SSRP1) which is highly expressed in GN. SSRP1, acting as both histone chaperone and transcription elongation factor, have important role in animal cell differentiation. To illuminate the function and mechanism of SSRP1 in pollen cell differentiation process, we will do following experiments: (1) Analysis the expression pattern of SSRP1 during the cell differentiation process of Lily pollen; (2) Screening and verification the interacting protein of SSRP1; (3) Verification the effect of SSRP1 in regulating gene transcription of known cell differentiation regulators in pollen; (4) Observation the pollen phenotype of ssrp1 in Arabidopsis and then complemented with Lily gene. At last, this study will provide a new clue for the research of pollen cell differentiation.

细胞分化命运调控机制是发育生物学研究的重点，而花粉是研究植物细胞分化命运的理想体系。申请人对百合花粉的营养细胞和生殖细胞的核蛋白研究发现，SSRP1在生殖细胞中显著高表达。SSRP1具有组蛋白伴侣和转录延长因子的功能，已证明在动物细胞分化命运调控中发挥重要作用。为明确并阐明SSRP1在花粉细胞分化命运中的功能，本研究以百合花粉为材料，在前期研究的基础上，拟开展以下工作：（1）解析SSRP1在百合花粉细胞分化过程中的表达模式。（2）SSRP1相互作用蛋白的筛选和验证。（3）验证SSRP1对已知分化调控基因的影响；（4）对拟南芥ssrp1突变体花粉进行表型观察，并对该突变体进行互补验证。以期达到的研究目标为：（1）确定SSRP1在花粉细胞分化命运中的作用。（2）阐明SSRP1调控百合花粉细胞命运分化的机制。本项目研究意义是为解析花粉细胞分化命运机制提供新的线索或突破点。

细胞命运分化调控机制是发育生物学研究的重点，而花粉是研究植物细胞分化命运的理想体系。本研究以百合花粉为材料，分离纯化出营养细胞核和生殖细胞核，并对二者核蛋白进行基于iTRAQ标记的定量质谱鉴定，鉴定差异蛋白720个，首次解析花粉营养细胞和生殖细胞的核蛋白差异图谱，并发现营养细胞和生殖细胞在染色质状态、表观修饰、核膜形态、转录因子、代谢及泛素化降解途径等方面存在显著差异；此外，组学数据发现SSRP1在生殖细胞中显著高表达，SSRP1作为FACT复合体的亚基，具有组蛋白伴侣和转录延长因子功能，被证明在动物细胞命运分化调控中发挥重要作用。本项目通过免疫印迹的方法验证了SSRP1在花粉的生殖细胞高表达；亚细胞定位显示SSRP1定位于细胞核；对拟南芥ssrp1突变体花粉进行表型观察发现，ssrp1影响植株生长、花粉萌发率以及结实率；通过IP-MS的方法鉴定到SSRP1潜在的互作蛋白120个；该研究首次揭示了花粉营养细胞和生殖细胞的核蛋白差异图谱，并围绕SSRP1开展机制研究，为解析花粉细胞分化命运机制提供新的线索或突破点。