控制水稻精米蛋白质含量的主效QTL克隆及育种基础研究

The genetic dissection of the mechanism underlying rice quality formation is the prerequisite for the improvement of rice quality. Protein content (PC) in milled rice not only is tightly associated with rice nutrition quality, but also plays an important role in determining the eating and cooking quality, togethe with amylose content in endosperm. However, there is little information accumulated about the genetic mechanism of on PC so far, and less understanding of key genes/QTL controlling PC variation in rice germplasm. In our previous study, a chromosome segment substitution line (CSSL) population derived from a cross of Sasanishiki(japonica)/Habataki (indica) was employed to detect the major QTL for PC, two stably expressed QTL with major effect, qPC-1 and qPC-10, were successfully identified, and the finely-mapping of qPC-1 was also performed. Therefore, we plan to further dissect the genetic mechanism of PC in milled rice with three aspects: (1) To construct mapping population through crossing SL402 (qPC-1) and SL427 (qPC-10) with recurrent parent Sasanishiki, respectively, for fine mapping qPC-1 and qPC-10 with the help of progeny test; (2) To obtain the candidate gene of qPC-1 by transgenic approach and sequence comparison of ORFs in target region among typical indica/japonica varieties, and then understanding the molecular function of candidate gene; and (3) To clarify the genetic effects of qPC-1 and qPC-10 in rice quality improvement practice through the introgression of two QTL into typical japonica cultivars. The result obtained in the project is expected to provide both clear knowledge on the genetic mechanism of PC variation in rice, consequently for rice quality improvement practice and the important gene resource.

稻米品质性状的遗传解析是高效进行品质改良的基础。精米中蛋白质含量（PC）的高低不仅决定稻米营养品质，也是影响稻米食味品质的关键因子。然而，关于PC的遗传研究比较匮乏，对控制PC变异的关键基因的了解更少。本课题组在前期的研究中，以粳稻Sasanishiki和籼稻Habataki衍生的染色体单片段代换系群体为材料，已经鉴定出两个稳定表达的主效QTL，qPC-1和qPC-10，并对qPC-1进行了较为精细的定位。本研究拟在此基础上，（1）以分别携带有qPC-1和qPC-10的单片段代换系SL402和SL427与Sasanishiki回交、自交构建定位群体，结合后裔表型鉴定，精细定位两个QTL；（2）通过转基因、籼粳品种的序列比较，确定qPC-1的候选基因，阐明其分子生物学功能；（3）通过回交转育，研明qPC-1和qPC-10的育种利用价值。本研究结果将为稻米品质的改良提供重要的依据和基因资源。

稻米蛋白质含量（PC）是一个非常重要的品质性状，不仅是衡量稻米营养品质的重要指标，也是影响稻米食味品质的关键因子。然而，关于PC的遗传研究比较匮乏，对控制PC变异的关键基因的了解更少。在前期的研究中，我们以粳稻Sasanishiki和籼稻Habataki衍生的染色体单片段代换系群体为材料，鉴定出两个稳定表达的主效QTL，qPC-1和qPC-10，并对qPC-1进行了较为精细的定位。本项目在此基础上，（1）进一步分析了水稻种质中蛋白质含量的变异，发现水稻蛋白质含量在籼粳亚种间表现明显的差异，一般籼稻的蛋白质含量高于粳稻，而且引起这些差异的主要原因是由于籽粒中谷蛋白含量差异造成的。（2）通过构建高代回交群体，分别精细定位了qPC-1和qPC-10，获得了qPC-1的候选基因LOC_Os01g55690和qPC-10的候选基因LOC_Os10g26060，并通过互补和敲除实验证明它们即为qPC-1和qPC-10的候选基因。序列分析表明，这两个候选基因的启动子序列在籼粳亚种间发生了变异，导致两个基因的表达水平发生了改变，进而影响了籽粒中谷蛋白的含量。在qPC-1和qPC-10两个QTL座位上，来自粳稻中的等位基因可以分别提高和降低籽粒中谷蛋白的含量。（3）根据LOC_Os01g55690 和LOC_Os10g26060启动子区的序列变异设计了功能性分子标记，并利用分子标记辅助选择将来自籼稻的等位基因qPC-1H导入粳稻中，发现籽粒的蛋白质含量可以降低1%以上，同时稻米的食味值可以显著提高，表明qPC-1对稻米品质的改良具有重要应用价值。该结果初步阐明了稻米蛋白质含量变异的分子机理，并为稻米品质的改良奠定了重要的理论基础，也为稻米品质改良提供了基因资源和分子标记辅助选择的工具，对稻米品质育种具有重要的推动作用。