拟南芥SSR1调控种子大小的分子机理研究

Seed is a basis of plant propagation, and is also an important agronomic trait. Despite the importance of seed size, relatively little is known about the genetic and molecular mechanisms that control seed size. Previously, we identified that the ssr1 mutants gave rise to larger seeds than the wild type in Arabidopsis. The average seed size of the ssr1 mutants was approximately 140% that of the wild type. Fully elongated ssr1 mutant siliques were longer and wider than wild-type ones. The seed numbers per silique of the ssr1 mutants was approximately 112% that of the wild type. Therefore, we thought SSR1 was a key factor of seed size control. Genetic experiments showed that SSR1 acted downstream of BR signaling and SHB1-MINI3 pathways that controlling the seed size. In this study, we will reveal the molecular mechanisms of SSR1 in seed size determination and establish a genetic and molecular framework of SSR1 for controlling seed size in Arabidopsis. The results will provide the important information to understand the mechanisms of seed size regulation and improve crop yield.

种子是植物繁殖的基础，其大小是决定植物产量的关键性状之一。因此，关于种子大小调控机制的研究一直受到人们的重视。本项目前期筛选到拟南芥种子变大的突变体ssr1（seed size regulator 1），其种子相比野生型显著增大，粒重增加约40%；同时突变体的角果变大，每个角果的种子数目增加约12%。因此SSR1是控制种子产量性状的关键基因。遗传分析显示，SSR1基因受到BR信号的调控，并作用于SHB1-MINI3途径的下游。本项目将在前期工作的基础上，进一步深入研究SSR1调控种子大小发育的分子机理，明确SSR1介导的分子遗传网络。研究结果将为理解种子大小决定的机理以及作物高产育种提供重要信息。

种子大小是直接决定产量的关键要素。揭示种子大小调控的遗传分子机制对于提高种子产量具有重要的理论和应用价值。拟南芥种子的大小主要由胚珠、胚和胚乳共同决定。尽管已经鉴定到多个调控种子大小的关键因子，但相关的信号通路仍然需要进一步深入研究。我们鉴定到一个拟南芥功能未知的基因SSR1，它编码一个丝氨酸-苏氨酸激酶，属于AGC VIIIa亚家族。ssr1-1突变体种子显著大于野生型的种子，同时超量表达SSR1基因能够降低种子大小。SSR1对种子大小的调控依赖于种子胚的细胞数量。为了进一步确定SSR1在调控种子大小中的功能，我们利用RNA测序和无标记定量磷酸化蛋白质组学技术对ssr1-1突变体和野生型授粉后3天的种子进行基因表达分析。RNA测序分析发现，有1611个在ssr1-1突变体中相对野生型差异表达的基因。聚类分析发现，这些基因参与细胞周期和胚胎发育等多种生物学过程。通过磷酸化蛋白质组学检测到262个差异磷酸化蛋白，主要参与细胞周期和胚后发育等调控过程。以上分析结果表明，SSR1是影响种子发育的关键因子，通过介导细胞增殖和胚胎发育等过程影响种子大小。本研究结果为丝氨酸-苏氨酸激酶SSR1调节种子大小提供了新的证据。