水稻淀粉分支酶IIb基因不同位点突变影响抗性淀粉合成和稻米品质形成的机制

摄食富含抗性淀粉（RS）的食物有利于人体健康，常规稻米RS极低，淀粉分支酶IIb（SBEIIb）突变能够提高RS含量，但影响稻米品质。不同文献或不同遗传背景水稻的研究表明，SBEIIb基因不同位点突变对RS和稻米品质的影响不同，但在相同遗传背景下上述影响及其机制知之甚少。本项目以粳稻Kitaake及其糯性突变体和它们来源的SBEIIb基因不同位点突变的水稻为材料，测定并查明SBEIIb突变对成熟籽粒稻米品质及淀粉结构和特性的影响。以发育胚乳为材料，观察胚乳组织结构，测定淀粉分子结构和淀粉合成关键酶的动态变化，分析贮藏物质的累积和胚乳转录组，探讨突变位点影响胚乳组分代谢的通路，阐明SBEIIb基因不同位点突变调控RS合成和稻米品质形成的机制。研究结果丰富和充实淀粉发育和特性、作物品质形成和调控等知识，为培育超重、肥胖、高血糖和高血脂等人群需要的高RS水稻新品系及其稻米的开发利用提供理论基础。

Eating foods with high resistant starch (RS) is beneficial for human health. However, the RS content in conventional rice kernel is very low. The mutation of starch branching enzyme IIb (SBEIIb) can improve the RS content in kernel, but affects the rice quality. The studies in different literatures or on rice materials with different genetic backgrounds show that the different mutation sites of SBEIIb gene have different effects on RS content and rice quality. However, the above effects and their mechanisms are known little in rice materials with the same genetic background. In order to identify the mutation site of SBEIIb gene having application value, we have created some rice mutants with different mutation sites of SBEIIb gene in the background of Japonica rice Kitaake and its glutinous mutant. In this project, we will determine and reveal the effects of different mutation sites of SBEIIb gene on the quality and starch structure of rice mature kernels. For developing endosperm, we will observe the endosperm tissue structure, investigate the dynamic changes of starch molecular structure and starch synthesis key enzymes, analyze the accumulation of storage materials and the endosperm transcriptome, and explore the effect of mutation sites on the metabolism pathway of endosperm components. The above studies on developing endosperm will elucidate the regulating mechanism of RS synthesis and kernel quality formation in rice through different mutation sites of SBEIIb gene. This project could enrich the knowledge of starch development and properties and quality formation and regulation in cereal crops, and provide theoretical basis for the cultivation and utilization of high RS rice needed by people suffered from overweight, obesity, hyperglycemia, and hyperlipidemia.