灌浆期硒高、低效水稻品种功能叶-籽粒系统中硒的“源”、“库”差异特征研究

Rice genotype differences in the accumulation of Se, and a high and a low Se accumulator have been selected from a large number of rice varieties. The different mechanisms of grain selenium accumulation between the two rice cultivars have been conducted on absorption and transport processes. Results showed that the Se mobility from leaves to grains is significantly higher in the high Se accumulator than in the low Se accumulator during filling stage, and it also affected the accumulation of selenium in grains of the two rice cultivars. However, the mechanism of the difference in mobility from leaves to grains is not clearly between the two rice cultivars. The high selenium and low selenium accumulators will be used as test materials, and this research main focus on the difference of selenium redistribution in leaf-grain system of the two rice cultivars. The redistribution level, mobility, transport path, transport forms, energy supply, transporters and the interaction with other elements of Se in leaves will be detected to elucidate the differences of selenium supply ability of leaves as "source" in the two rice cultivars. The sources, accumulative sites, chemical forms, combination forms, distribution and forms in ultrastructure of selenium in grains will be analysed to explore the differences of selenium loading ability of grain as "sink" in the two rice cultivars. And then to elaborate the differences in redistribution of Se from leaves to grains between the two rice cultivars. The solution of this scientific problem will be helpful to further understand the mechanism of the difference of grain selenium accumulation between the two rice cultivars.

水稻存在着硒高、低效的基因型差异，课题组从大量水稻品种中筛选出了硒高、低效水稻品种各1个，并且从吸收和转运上对二者籽粒硒累积量差异机制开展了研究。研究发现灌浆期硒高累积水稻功能叶硒被籽粒再利用的能力要显著强于低累积水稻，并且会影响到两个水稻品种籽粒中硒的累积量，但是目前尚不清楚两个水稻品种功能叶硒再利用能力存在差异的具体机制。本研究拟以硒高、低效水稻品种为试验材料，主要阐述两个水稻品种功能叶-籽粒系统中硒的再利用差异机制，从叶片硒的再利用水平、移动能力、运载路径、转运载体和能量供应、转运形态以及元素间的相互作用来分析叶片作为“源”对硒的供应能力差异，从籽粒中硒的来源、累积部位、化学形态、赋存形态、微区分布以及微区形态来探究籽粒作为“库”对硒的装载能力差异，进而阐述两个水稻品种功能叶硒被籽粒再利用的差异机制。该科学问题的解决还将有助于深入理解两个水稻品种籽粒硒累积量差异的机制。

水稻存在着硒高、低效的基因型差异，课题组从大量水稻品种中筛选出了硒高、低效水稻品种各1个，并且从吸收和转运上对二者籽粒硒累积量差异机制开展了研究。前期工作发现灌浆期硒高累积水稻功能叶硒被籽粒再利用的能力要显著强于低累积水稻，并且会影响到两个水稻品种籽粒中硒的累积量，具体机制不明。本项目以硒高、低效水稻品种为试验材料，主要阐述两个水稻品种功能叶-籽粒系统中硒的再利用差异机制，从叶片硒的再利用水平、转运载体、转运形态以及元素间的相互作用来分析叶片作为“源”对硒的供应能力差异，从籽粒中硒的累积部位、化学形态、微区分布来探究籽粒作为“库”对硒的装载能力差异，进而阐述两个水稻品种功能叶硒被籽粒再利用的差异机制。研究发现硒高累积水稻品种可以将更高比例原始累积在叶片中的硒迁出，而且多为有机态硒，高累积水稻品种有机硒转运蛋白基因NRT1.1B的相对表达量要显著高于低累积水稻品种，具有更强的载体蛋白；转运过程中高累积水稻品种组织内硒与其它多类别矿质元素的关系更加友好，协同效应更强，拥有更佳的转运环境，更加有利于硒的迁出。硒到达籽粒后，高累积水稻品种能将更多的硒转运至非胚端，低累积水稻品种则将更多的硒累积至胚端，高累积水稻品种合理利用籽粒库容的能力要显著强于低累积水稻品种；高累积水稻品种还能将更多的硒累积至种皮，而种皮是籽粒累积硒的关键部位之一。因此，高累积水稻品种在灌浆过程中能将更多的原始累积在叶片中的硒再次利用，并且能将更多的硒装载进籽粒。研究结果有助于从更深层次理解不同水稻品种籽粒累积硒存在差异的机制，同时为水稻增效富硒提供理论和技术支撑。