水稻MID1和赤霉素互作调控缺水条件下花粉发育的机制研究

Reproductive development determines production in crops. Frequent occurrences of drought during the reproductive stage results in low seed setting ratio and reduces yield in rice, seriously threating the safety of crop production. However, the study of how reproductive development is regulated in crops under water deficit is still lacking. We found that the genes involved in the biosynthesis of gibberellin(GA) and GA-related tapetum development were downregulated, while genes responsible for GA degradation were elevated in rice under water deficit, along with enlarged tapetum cells and abnormal microspores. MID1 (MYB Important for Drought Response1), encoding RR type MYB-like transcription factor and mainly expressed in tapetum cells and microspores, plays a role in buffering the expression of genes in GA-related tapetum development and improving tapetum development under water deficit. Therefore, we hypothesize that MID1 may interact with the GA pathway to regulate rice anther development under water deficit. To confirm our hypothesis, we will analyze the relationship between the expression pattern of MID1, the level of bioactive GA and the developmental stage of the anther, and we will explore the function of GA in regulating anther development under water deficit by exogenous application of GA3. In addition, we will analyze the co-regulated genes by MID1 and GA using RNA-seq and the genetic interaction between MID1 and the GA pathway to elucidate the molecular mechanism underlying the regulation of pollen development in rice by the interaction between MID1 and GA. Our study will provide some theoretical support to maintain high and stable yield, and to save water in crop production under water deficit.

作物生殖发育是产量形成的决定过程。生产实践中，生殖期干旱少雨，导致水稻结实率和产量显著降低，严重影响粮食生产安全。但基础生物学研究领域对缺水条件下植物生殖发育调控研究相对缺乏。申请者发现缺水引起水稻花赤霉素(GA)合成和GA相关绒毡层发育基因下调、GA降解基因上调，花药绒毡层膨大，小孢子发育异常。RR类MYB-like转录因子MID1在水稻花药绒毡层和小孢子中表达，且能稳定缺水条件下绒毡层发育基因表达并改善绒毡层发育。由此，推测MID1可能与GA互作调控缺水条件下水稻花粉发育。为验证此假设，拟分析水稻MID1表达、活性GA含量与花粉发育阶段的关联性；外施GA3，以探索GA在缺水条件下调控花粉发育的作用；转录组分析GA和MID1共调控基因，结合遗传和染色质免疫共沉淀实验，以明确MID1与GA互作调控缺水条件下水稻花粉发育的机制，为缺水条件下作物高产、稳产和节约农业用水量的问题提供理论支持。

作物生殖发育是产量形成的决定过程。重要粮食作物水稻在生殖期面临干旱，其结实率会显著降低，严重时会导致绝产，影响粮食生产安全。但基础生物学研究领域对缺水条件下水稻生殖发育调控研究相对缺乏。在前期研究基础上，我们提出“MID1与GA互作调控缺水条件下水稻花粉发育并改善产量”的科学问题。为解决此问题，首先分析水稻MID1表达、活性GA含量与花粉发育阶段的关联性；接下来外施活性GA，以探索GA在缺水条件下调控花粉发育的作用；最后利用转录组测序分析GA和MID1共调控基因，结合遗传和染色体免疫共沉淀实验，以明确MID1与GA互作调控缺水条件下水稻花粉发育的机制。根据项目的设计，我们基本上完成了研究目标。.我们研究发现，干旱导致水稻花药中GA合成基因表达下降和GA降解基因表达上调，引起花药中活性GA含量下降。体外施加活性GA改善干旱条件下水稻花粉发育和活力。受干旱诱导表达的MID1基因也受GA调控表达，MID1在水稻双核期花粉中表达量高且主要定位在水稻花药绒毡层和小孢子中。进一步研究发现，GA和MID1共同改善干旱条件下花药绒毡层发育；且干旱条件下，过表达MID1可以缓冲GA通路绒毡层发育相关基因的变化。ChIP-PCR和荧光素酶实验表明，MID1直接结合KAR基因启动子并激活其表达。我们还发现，MID1与SPL14互作并抑制SPL14蛋白的功能去影响作物产量性状。本项研究阐明了缺水条件下MID1与GA互作调控水稻花粉发育的分子机制，为缺水或少水条件下作物的高产、稳产和节约农业用水量的问题提供理论支持和技术保障。.