油菜素甾醇、多胺与乙烯对水稻颖花退化的调控及其机理

Spikelet degeneration in rice is a major limiting factor to the realization of yield potential. The mechanism underlying the spikelet degeneration is yet to be understood. We have got a mutant which exhibits a high rate of spikelet degeneration. When compared with the wide type, the mutant showed no significant difference in the content of endogenous cytokinins, indole-3-acetic acid, gibberellins, and abscisic acid. However, the levels of brassinosteroids (BRs) and polyamines (PAs) were significantly lower, and the ethylene evolution rate was significantly higher, in the mutant than in the wide type. Application of BR, PA or an ethylene inhibitor could markedly decrease the rate of spikelet degeneration. With the mutant and other rice varieties (including super rice) differing in the rates of spikelet generation, this proposed project aims to investigate (1) the relationships of BRs, PAs, and ethylene with other hormones and their interactions on regulating spikelet degeneration, (2) the physiological and molecular mechanisms underlying the regulation of BRs, PAs and ethylene and their interaction to/on spikelet degeneration, and (3) responses of endogenous BRs, PAs and ethylene to soil moisture, nitrogen, phosphorous and potassium and their relations with spikelet degeneration, the indexes of soil moisture and the content of nitrogen, phosphorous and potassium in the plants, and the management techniques of water and fertilizers for reducing spikelet degeneration in rice. The output of the proposed project will be able to obtain new knowledge in understanding the mechanism involved in spikelet degeneration, explore new regulatory approaches to decrease spikelet degeneration, and to provide theoretical and practical guidance to high-yielding breeding and cultivation in rice.

水稻颖花退化是限制产量潜力发挥的一个重要因素。目前对颖花退化的机理不清楚。本项目组找到一个颖花退化率高的突变体。与对照(野生型)相比，突变体内源细胞分裂素、生长素、赤霉素和脱落酸含量没有显著差异，但内源油菜素甾醇(BRs)和多胺(PAs)含量显著降低，乙烯释放速率显著增高。使用外源BR、PA或乙烯合成抑制剂可显著减少颖花退化。本项目以该突变体和颖花退化率不同的水稻品种为材料，主要研究：（1）BRs、PAs和乙烯与其它激素的关系及其对颖花退化的调控作用；（2）BRs、PAs和乙烯及其相互作用调控颖花退化的生理与分子机理；（3）BRs、PAs和乙烯对土壤水分、氮、磷、钾响应特点及其与颖花退化的关系，协调内源BRs、PAs和乙烯水平以减少颖花退化的土壤水分、植株氮、磷、钾指标与调控技术。本项研究可望获得对水稻颖花退化机理的新认识，开发减少颖花退化的新途径，为水稻高产育种与栽培提供理论和实践指导。

理解水稻等谷类作物颖花或小花退化问题是一个科学难题，减少颖花退化是进一步提高产量的重要途径。为解决这一难题，本项目研究了植物激素对水稻颖花退化的调控作用及其机理，减少颖花退化的栽培技术及其调控原理，获得了重要结果: (1) 油菜素甾醇(BRs, 主要为24-表油菜素内酯和28-表高油菜素内酯)、多胺(PAs,主要为亚精胺和精胺)和乙烯对水稻颖花退化起重要调控作用。减数分裂期增加幼穗中BRs和PAs含量可减少颖花退化，增加乙烯水平则可增加颖花退化，BRs和PAs对调控颖花退化有累加的协同效应；(2) BRs、PAs和乙烯通过调节幼穗中能量代谢和活性氧水平，调控颖花退化；在减数分裂期提高幼穗中BRs和多胺含量、降低乙烯水平，可以提高幼穗中能量水平和抗氧化能力，进而减少颖花退化，提高产量；(3) 在幼穗发育期采用适度土壤干旱(土壤水势不低于-10 kPa)或当植株含氮量<2.5%时施用氮肥，可以增加幼穗中BR和PAs含量，降低乙烯水平，提高幼穗能量水平和抗氧化能力，进而促进颖花分化和减少颖花退化；(4) 创建了 “一种水稻节水灌溉方法”、“一种依据水稻叶色相对值追施氮肥的方法”，可有效减少水稻颖花退化，提高产量，在生产上示范应用取得了高产与水分养分高效利用的效果。这些结果是对水稻颖花退化机理的新认识，为减少水稻等谷类作物颖花或小花退化、提高产量潜力提供了新途径，对指导水稻高产育种与栽培有重要的科学意义和实践意义。本项目发表论文22篇，其中SCI收录论文14篇；申请发明专利5件，其中授权3件；培养研究生12名（含博士生4名）；研究成果“促进稻麦同化物向籽粒转运和籽粒灌浆的调控途径与生理机制” 获2017年度国家自然科学奖二等奖。