水稻籽粒中调控造粉体发育关键基因FLO10的功能分析

Starch content in rice seeds accounts for over 90% of the total weight, so the accumulation of starch plays an important role in the formation of rice yield and quality. The process of starch synthesis is complicated and sophisticated which requires the participation of many enzymes and regulatory factors. At last, starch is converted to starch granules and stored in amyloplast. Studies on some new opaque endosperm mutants showed that these new genes can not be added into the old model which has been established, so we need to construct a bigger or a cross model using those novel mutants. The floury endosperm10 (flo10) was screened from rice mutant lines. The flo10 showed complete floury endosperm and the chloroplast and amyloplast of flo10 was significantly larger than wild type. Map-base cloning was shown that FLO10 encoded SecY2 protein. SecY2 protein is the basic protein in Sec2 system and the function of Sec2 system is largely unknown. Next, we will we intend to conduct a series of studies to clarify the function of Sec2 system and its function in the process of amyloplast development.

水稻中淀粉含量占种子总重量的90%以上，淀粉的积累对于水稻产量和品质的形成具有极为重要的意义。淀粉的形成是一个复杂且精密的过程，需要许多酶类和调控因子的参与，最终淀粉在造粉体内被转化为淀粉颗粒并储存起来。这一模型已经初步建立，但随着越来越多该模型外的粉质基因的发现，建立新的多网络交叉模型就显得尤为重要。前期我们从水稻突变体库中筛选到了粉质突变体flo10， flo10表现为胚乳完全粉质，并发现其造粉体和叶绿体显著增大。通过图为克隆及转基因互补验证发现FLO10编码SecY2蛋白。SecY2蛋白是Sec2系统的关键蛋白，而Sec2系统在植物中的功能尚不清楚。下一步我们拟开展一系列的研究阐明Sec2系统的功能和其在造粉体发育过程中的功能。

淀粉是稻米中的主要物质，淀粉的含量和组成是决定稻米品质的最重要因素。淀粉的合成主要在胚乳造粉体中完成，因此造粉体发育的研究对我们解析复杂的淀粉合成过程至关重要。我们筛选到了粉质突变体flo10，突变体表现为胚乳粉质，其淀粉含量显著降低。同时我们发现突变体的造粉体和叶绿体显著增大。通过图位克隆及转基因验证发现FLO10编码SecY2蛋白，酵母双杂交和BiFc实验证明SecY2和SecA2及SecE2互作组成Sec2复合物。进一步通过不同定位的叶绿体蛋白在野生型和突变体中的定位观察发现叶绿体内膜蛋白Tic40发生了由膜定位到点状的变化，互作实验也证明了该结果。进一步分析我们认为Sec2系统可能参与到质体未知的Post-insertion途径。同时证实了Post-insertion途径定位到叶绿体内膜的必要元件，实现了任意肽链的质体内膜定位。利用该模型我们还找到了两个利用Post-insertion途径定位到质体内膜的蛋白。利用CRISPR/Cas9敲除Tic40，其突变体也表现为胚乳粉质表型。综上，我们阐明了Sec2系统通过参与质体Post-insertion途径调控造粉体发育，同时详细阐明Post-insertion途径的元件并实现人工操控。