油菜素类固醇(Brassinosteroids,BRs)对水稻籽粒灌浆的影响及其生理与分子机制

Grain filling is the material basis for the formation of rice yield, starch and other constituents are produced and accumulated in rice grain through this filling process, whereas slowness of grain filling in inferior spikelets is a major limiting factor for the increment of rice yield. Studies have shown that the grain filling rate was affected by many factors, such as the speed of endosperm cell division and growth, the activities of enzymes related to starch synthesis, and the grain filling rate is also subject to regulation of a variety of plant hormones. As an high efficient phytohormone，brassinosteroids (BRs) have been paid attention for their effects on rice seed set and grain weight, but it is far away from recognizing systematically the BR's regulatory pathway and acting mechanisms on rice grain filling, especially for it's molecualr regulation aspect. We try to carry out a series of experiments on morphology，anatomy, physiology，biochemistry and molecular biology in many respects, which including the growth and development of rice panicle, spikelet and endosperm cell, starch synthesis and the activities of its related enzymes, and also includeing the metabolism and regulation of inner phytohormone, so as to elucidate the BR's effects on rice grain filling and its related physiological and molecular mechanisms. These researches can provide some scientific bases for increasing grain filling rate as well as rice yield through the hormonal and even molecular regulatory pathway.

籽粒灌浆是水稻产量形成的物质基础，灌浆过程就是淀粉等物质产生并积累的过程；而弱势粒灌浆差是水稻增产的主要限制因素。已有研究表明：水稻籽粒灌浆速率受籽粒形成过程中胚乳细胞分裂和生长快慢及淀粉合成相关酶活性高低等诸多因素影响，并受到多种植物激素的调控；作为一类广谱、高效的植物激素，油菜素类固醇（brassinosteroids,BRs）对水稻结实率和粒重的影响已引起人们的广泛关注，但BRs影响水稻籽粒灌浆的具体调控途径和作用机制目前还不是很清楚，其分子调控机制更是知之甚少；本项目计划运用形态解剖学、生理生化和分子生物学的研究手段，从穗粒和胚乳细胞生长发育、淀粉合成及其相关酶活性和激素代谢、调控等多方面对BRs影响水稻籽粒灌浆的生理与分子机制进行系统深入的研究，本项目的研究结果将为通过激素及分子调控途径提高籽粒灌浆速率和水稻产量提供理论依据。

为了系统研究BRs对水稻籽粒灌浆的影响及其生理与分子机制。我们设置了如下试验：首先，为系统阐明BRs协调水稻源强、库容和库活性之间的关系及其生理生化机制，我们在大田条件下，以粳稻日本晴为试验材料，在穗分化期喷施2,4-表油菜素内酯(2,4-epibrassinolid, EBR)，进而分析其叶片及茎鞘内非结构性碳水化合物(non-structure carbohydrate, NSC)花前积累以及籽粒灌浆过程中碳同化物代谢、转运和转化的情况，并结合生长发育的变化以及强、弱势粒籽粒灌浆的结果，明确穗分化期外施EBR对水稻穗粒发育和籽粒灌浆的影响及其作用的生理机制。然后，我们以水稻台中65（TZ65）为背景的BR受体OsBRI1编码基因发生点突变的突变体Fn189(osbri1)为研究对象，通过表型分析、产量和产量构成因子分析，生理生化测定并结合质谱分析和蛋白质组生物信息学分析，更进一步地验证了BR调控水稻穗粒发育和籽粒灌浆的生理生化机制，初步揭示了BR调控水稻籽粒灌浆的分子机制。本项目研究获得的结果为通过激素及分子调控途径促进水稻穗粒发育和籽粒灌浆奠定了依据。