谷子穗发育调控基因LaxP1的图位克隆及功能分析

Panicle development is a major component determining crop yield. Identify novel genes as well as their regulatory mechanisms that control panicle development is predominant for crops molecular breeding. Setaria italica is proposed as an ideal model for functional gene study, especially for research on C4 photosynthesis and drought tolerance. Here, an abnormal panicle development mutant was isolated from S. italica EMS-induced mutant library, which has significantly less primary branches and florets compared to wild type. The casual gene LaxP1 was identified through map-based cloning. Based on our data, we will firstly investigate the dynamic morphology and physiological changes of the laxp1 mutant at different development stages. Then, we will study the molecular mechanisms of LaxP1 and determine the biological significance of its regulation roles on panicle development, using integrative approaches of genetics, plant physiology, biochemistry, molecular biology, and bioinformatics. In addition, we will perform systematic analysis of haplotypes of LaxP1 from different foxtail millet varieties, and identify novel alleles contributing to crop yields. Candidate alleles will be transformed into foxtail millet, rice, and wheat through genetically modification method to test their roles in crop yield improvement. Our study may pave a new way for understanding the molecular mechanism of plant panicle development, and provide new gene resource for crop breeding.

穗部性状是影响农作物产量的主要性状，发掘新的穗发育调控基因并解析其机理是高产分子育种的基础。谷子正发展成为C4旱生禾谷类作物基因功能研究的新模式植物。本实验室从谷子EMS突变体库中鉴定到1份穗发育异常的突变体，其一级枝梗数和小花数均显著低于野生型。利用图位克隆技术我们分离得到目标基因LaxP1。本项目将对突变体表型进行系统分析，理清laxp1穗发育异常的形态学和细胞学基础；然后综合利用遗传学、植物生理学、生物化学、分子生物学和生物信息学等手段，深入研究LaxP1基因的功能和分子作用网络。同时，我们在谷子核心种质资源中对LaxP1基因进行单倍型分析，发掘对产量有正向贡献的优异等位基因，并将其导入谷子主栽品种和水稻、小麦两个主粮作物中，检测其增产潜力。本研究将丰富作物穗发育调控的分子机理并为作物产量性状遗传改良提供新的基因资源。

穗顶端小花退化对禾本科作物最终产量形成有重要影响。谷子是我国重要的杂粮作物，但目前关于谷子穗顶端退化的遗传和分子机制的研究较少。本研究在谷子中鉴定到一个穗顶端退化突变体simnt1。我们通过农艺性状调查和表型分析明确了该突变体基本特征。通过深入的组织学、细胞形态学显微观察，明确了simnt1穗部发育异常的形态学和细胞学基础。通过图位克隆和高通量测序结合的方法定位了目标基因SiMNT1，并对SiMNT1进行转基因功能验证和分子机制解析。研究明确了SiMNT1的表达特征，和Mn离子转运蛋白的具体功能，以及其调控谷子穗发育的分子通路，并发掘到了该基因在育种中的优异单倍型，为杂粮作物产量性状遗传改良提供基因资源和理论基础。同时，我们通过本项目建立了谷子功能基因的研究体系，并利用该系统鉴定和解析了SiAUX1, SiBOR1, SiSGDW1以及SiMADS34四个和谷子穗部发育密切相关的基因，丰富了本项目的研究成果，为了谷子功能基因发掘及育种利用提供了丰富的基因资源。