灌浆温度对水稻贮藏蛋白合成与籽粒碳-氮代谢互作的影响机理

The influences of air temperature on the expression profile and their spatiotemporal patterns of multigenes coding for the process of the precursor synthesis, subunit folding-assembling of storage protein metabolism in filling grains shall be investigated under the controlled temperatures by using two mutation rice materials differing in grain storage protein components, assisted with a comprehensive analysis for their difference in the components structure, morphological distribution, binding states of starch-protein complex, and also metabolite profiling of major and minor compounds in grain carbon-nitrogen metabolism among different temperature treatments. Moreover, the molecular technique of RNAi interference and overexpression for several regulatory genes in grain nitrogen metabolizing pathway shall be also appiled to domenstrate the response of some function genes to enviromental temperature and its relation to grain storage protein accumulation. The objectives of this project are: i) to identify the regulatory gene locus and its molecular ecological mechanism of enviromental temperature impacting grain storage protein synthesis and its component accumulation; ii) to clarify the alteration of assimilating transportation, regultory network and cooperative interaction between carbon-nitrogen metabolism in filling grains as affected by temperatur after assimilating substances enter sink organs as well as their relations to nutritional and cooking quality. Such expectant results can provide helpful knowledge for future genetic and agronomic improvement of rice quality to probe the coordination both in nutritional quality and desirable cooking quality, as well as to provide new theoretical fundation and guide way to the improvement of grain quality traits for many cultivars with poor ecological stability in rice production by the modified cultivation management.

以人工控温试验为基础，通过对不同温度处理下发育胚乳中蛋白前体合成、亚蛋折叠和组装等代谢环节相关功能基因的表达谱及其时空变化特点的较全面检测，结合对不同温度处理下籽粒贮藏蛋白的组分结构、形态分布、淀粉-蛋白复合体结合态和籽粒碳-氮代谢相关中间产物组分的理化检测与代谢谱分析，以及相关重要功能基因RNAi沉默和超表达后的相关验证，阐明灌浆温度对水稻胚乳蛋白合成与相关代谢环节产生调控的主要功能基因位点及其调控的分子生态效应机理，揭示同化产物进入库器官后，籽粒碳-氮转运过程间的代谢互作与协同生理关系及其品质效应。本项目预期研究结果，不仅对于我国现阶段的稻米品质改良工作正面临营养品质与食味品质相协调、品质生态稳定性等问题的解决具有重要指导意义，可为进一步开展籽粒碳-氮代谢相协调与合理分配问题的栽培调控研究提供新思路和理论依据。

水稻籽粒蛋白质含量的高低及其组分变化，不仅是影响稻米营养品质的一个重要指标，而且与稻米蒸煮食味品质也存在密切联系。本项目利用人工气候箱控温度试验，对灌浆结实期不同温度处理下水稻籽粒贮藏蛋白合成代谢变化及其与稻米贮藏蛋白组分、蛋白亚基构成及碳水化合物代谢（蔗糖卸载和淀粉合成）之间的关系进行了较系统地研究分析。主要研究结果如下：1）灌浆高温会抑制水稻籽粒醇溶蛋白13KDa亚基的生物合成，导致水稻籽粒中的醇溶蛋白含量下降和谷蛋白/醇溶蛋白比值上升；2）灌浆高温对水稻发育籽粒中GluA-1、GluA-2、GluA-3、GluB-4和GluB-5的转录和蛋白表达量有显著影响，从而促进57KDa谷蛋白前体在水稻籽粒灌浆前期的生物合成。与此同时，57KDa的谷蛋白前体可进一步被裂解成37-39 KDa 的酸性亚基和 20-22 KDa 的碱性亚基，提高谷蛋白在水稻籽粒灌浆前中期的合成积累，但高温处理会引起水稻籽粒灌浆后期谷蛋白合成代谢的迅速下降；3）高温胁迫所引起水稻籽粒谷蛋白前体合成与裂解代谢受PDI的调控。PDI在高温胁迫下的转录和蛋白表达量上升，有利于促进水稻籽粒中谷蛋白前体向22 KDa成熟亚基的转化，而PDI基因沉默对谷蛋白前体（57KDa左右）裂解为22KDa碱性亚基有较明显的抑制作用；4）灌浆结实期高温除对发育籽粒中的贮藏蛋白合成和淀粉积累代谢产生较明显影响外，还可通过调节SnRK1a、RISBZ1和RPBF等基因或转录因子的表达，对籽粒碳氮分配代谢产生调控效应。其中，在蔗糖卸载环节，INV途径的蔗糖裂解过程在高温处理下受到抑制，而SUS途径的蔗糖裂解过程被增强。上述研究结果，对于进一步阐明灌浆温度对水稻贮藏蛋白合成积累与组分结构的影响机理及其品质效应具有重要理论意义。