氮素调控籼粳杂交稻蒸煮食味品质的理化基础与生理机制

Most indica-japonica hybrid rice released and planted currently are relatively poor in eating and cooking quality (ECQ). However, little is known about the physicochemical properties for it and its physiological responses mechanism to high nitrogen level. Accordingly, the research will be conducted to clarify the intrinsic factors and regulatory mechanisms for poor ECQ in indica-japonica hybrid rice under high nitrogen condition. Two types of indica-japonica hybrid rice and conventional japonica rice were selected as materials, and the ECQ and physicochemical properties were compared among them under different nitrogen treatments. As the starch and protein are the dominating role for ECQ, we will investigate the effects of nitrogen on synthetic metabolism of starch and protein during grain filling stage, so as to elucidate the physiological mechanisms underlying nitrogen regulation on the formation of ECQ in indica-japonica hybrid rice. The results obtained would enrich the theories of quality formation for rice, and also provide a support for breeding and cultivation of high quality rice.

籼粳杂交稻品种具有较高的产量潜力，但其潜力的充分释放依赖于较高的氮肥投入，致使稻米品质尤其是蒸煮食味品质显著低于常规粳稻。目前，尚未清楚高氮投入下籼粳杂交稻米质变劣的理化基础与生理机制。本项目以籼粳交偏籼型、籼粳交偏粳型和优质常规粳稻等南方粳稻代表性类型品种为材料，设置不同的氮素运筹，比较籼粳交组合与常规粳稻之间蒸煮食味品质和理化基础的差异，明确籼粳杂交稻蒸煮食味品质欠佳的关键理化因子。进而，基于碳氮代谢及其互作关系，利用组学与现代生化分析技术探查氮素对淀粉和蛋白质合成的影响机制，阐明氮素调控籼粳交稻米蒸煮食味品质形成的生理基础。研究结果将为籼粳杂交稻的遗传改良和优质栽培提供理论参考。

籼粳杂交稻具有较高的产量潜力，但其潜力的充分释放依赖于较高的氮肥投入，致使稻米品质尤其是蒸煮食味品质显著低于常规粳稻。目前，尚未清楚高氮投入下籼粳杂交稻米质变劣的理化基础与生理机制。本项目以籼粳交偏籼型和籼粳交偏粳型为材料，设置不同的氮素运筹，通过比较不同籼粳交组合之间及其强弱势粒之间稻米蒸煮食味品质和理化特性的差异，明确籼粳杂交稻蒸煮食味品质欠佳的关键理化因子。利用多组学技术探查强弱势粒间蛋白质合成的差异机制，初步阐明氮素调控籼粳交稻米蒸煮食味品质形成的生理基础。本研究结果表明：（1）在直连淀粉含量差异不大的背景下，淀粉颗粒大小是决定米饭质地的主要因素之一。支链淀粉中B1链较多而A链较少的淀粉糊化温度较高。因此，筛选低直连淀粉含量、小淀粉颗粒以及B1链较少的品种，有望得到高产优质的籼粳交组合。（2）高氮下，弱势粒比例随施氮量增加而显著增加，且弱势粒含有较高的醇溶蛋白，弱势粒的增加是导致食味品质大幅下降的关键因子。不同类型的籼粳杂交稻对氮素响应存在差异，偏籼型甬优17比偏粳型甬优12更敏感的主要原因在于弱势粒增加的幅度更大。（3）弱势粒的醇溶蛋白含量显著高于强势粒，而谷蛋白含量在两者间无显著差异。在籽粒发育过程中，弱势粒中鉴定到26种“关键差异代谢物”，根据表达模式，可将这些差异代谢物分为3类。通过加权基因共表达网络分析，发现两个模块的基因分别与核糖体蛋白质合成和应激反应密切相关。在模块基因中，共鉴定到8个核心基因。此外，13 kD醇溶蛋白合成基因及蛋白二硫键异构酶编码基因PDI5;1和重链结合蛋白编码基因Bip1显著上调。弱势粒中的乙烯含量较高，参与了调控蛋白质的合成。