油菜素甾醇和脱落酸对水稻颖花退化的调控作用与机理

The spikelet degeneration of rice (Oryza sativa L.) is a main constraint to grain yield, and solving the problem of spikelet degeneration is a very difficult problem in science. We have observed that brassinosteroids (BRs) and abscisic acid (ABA) play important roles in mediating spikelet degeneration of rice. However, the mechanism underlying is little understood. Therefore, this project will mainly study: (1) changes in BRs and ABA contents and their signal transduction characteristics in major organs (the root, stem, leaf and young panicle) at meiosis and pollen completion and their relationship with spikelet degeneration (including apical part spikelets and basal part spikelets) in the rice varieties/lines differing spikelet degeneration rates (including rice mutants); (2) The interrelationships among the BRs and ABA contents and their signal transduction, energy status, panicle-antioxidant capacity, and spikelet degeneration; (3) BRs and ABA in responses to soil moisture, nitrogen fertilizer, and the effect of exogenous BRs and ABA application on spikelet degeneration, and their roles and mechanism in regulating spikelet degeneration. This study is expected to elucidate the mechanism underlying rice spikelet degeneration, and put forward the cultivation or chemical approaches to reducing spikelet degeneration through regulating the levels of BRs and ABA in rice.

水稻颖花退化是限制产量的重要因素，解决颖花退化问题是一个科学难题。我们近期的研究发现，稻穗中油菜素甾醇(BRs)和脱落酸(ABA)对颖花退化有重要的调控作用，但其机理不清楚。因此，本项目主要研究：(1) 颖花退化率有明显差异的不同水稻品种/品系(含突变体)在减数分裂期和花粉充实完成期主要器官(根、茎、叶、幼穗)中BRs和ABA含量变化、信号传导特点及其与颖花(含穗顶端颖花与穗基部颖花)退化的关系；(2) BRs和ABA含量及其信号传导-幼穗能量状态-幼穗抗氧化能力-颖花退化的内在联系；(3) 水稻内源BRs和ABA对土壤水分和氮肥的响应及其对颖花退化的调控作用与机理，外源BRs和ABA对水稻颖花退化的调控作用与机理。揭示水稻内源BRs和ABA调控颖花退化的作用与机制，提出通过调控内源BRs与ABA水平以减少颖花退化的栽培与化学调控途径与技术。

颖花退化是限制水稻实现进一步高产的重要因素。本项目研究了油菜素甾醇(BRs)和脱落酸(ABA)对水稻颖花退化的调控作用与机理，获得了重要结果。(1)发现水稻颖花退化状况受减数分裂期前后幼穗中BRs与ABA水平的调控。稻穗中提高的BRs水平可有效减少颖花退化；ABA对颖花退化的正向或负向调控，取决于其剂量，一定范围内适度增加稻穗中ABA含量可有效减少颖花退化，但ABA水平过高会增加颖花退化；减数分裂期稻穗中增加的BRs和适度增加的ABA水平对减少颖花退化有累加的协同效应。(2)发现在减数分裂期协同提高稻穗中的BRs与ABA水平可显著提高幼穗中抗坏血酸-谷胱甘肽循环体系的强度，减少活性氧的过量积累及其对幼穗细胞的伤害，进而有效减少颖花的退化。(3)提出了减少颖花退化的调控技术：在减数分裂期采用轻度土壤落干(土壤水势保持在-10 ~ -15 kPa)或当植株含氮量<2.6%时施用氮素保花肥(雌雄蕊分化期施用)，可以有效协调幼穗中BRs和ABA水平，显著减少颖花退化、提高产量。本项目已发表论文11篇，其中SCI论文9篇；培养博士研究生1名、硕士研究生4名。