水稻少分蘖矮秆基因RTD1的克隆及功能研究

Tiller number and plant height are two major factors for determining of the rice architecture,and had been extensively application in rice high-yield breeding. Although there are a few genes controlling of tillering and plant height to be cloned, however, the understanding of regulation mechanisms of tillering and plant height is still very limited. To further explore the fine regulation mechanism of rice tillering and plant height, we identified a reduced- tiller number and plant height mutant, rtd1, and try to clone it by map-based approach. RTD1 had been delimited onto chromosome 4 within a physical distance of 600-kb firstly and an enlarged F2 segregation population had been developed to fine-map and clone the RTD1 gene. To verify the target gene is indeed RTD1, several experiments will be performed, such as the functional complementation experiments, transferred genes as well as in-situ hybridization studies. Those experiments should be applied to determine the expression pattern of RTD1. RNA-seq and yeast two-hybrid technologies will also be used to screen the downstream candidate genes and RTD1 interacting proteins. Furthermore, by constructing double mutant of rtd1 with known reduced-tillering mutants and exogenous hormones treatment, such as Gibberellin and strigolactone, the relationship of hormones and tiller number and plant height will be explored further. This project is not only important theoretical value to clarify the plant tillering and plant height control mechanism, will also contribute to agricultural production in the rice architecture improvement to provide a theoretical basis for the high-yield rice breeding.

分蘖数目和株高是影响水稻株型的主要因素，是影响产量的重要农艺性状，在水稻高产育种中具有重要意义。虽然已有几个控制分蘖和株高基因被克隆，然而人们对于水稻分蘖和株高的调控机理认识还十分有限。本研究通过分离一个水稻分蘖数目和株高减少突变体rtd1，以图位克隆方法克隆该基因，并通过功能互补实验验证其功能；通过转基因及原位杂交等技术研究RTD1基因的表达模式；利用RNA-seq技术鉴定RTD1的下游候选基因；利用酵母双杂交系统筛选与其RTD1相互作用的蛋白；通过构建双突变体方法鉴定RTD1与已知分蘖数目减少基因的遗传学关系；通过外施多种激素探讨激素与分蘖数目和株高间关系。本项目的研究不仅对阐明水稻分蘖和株高的控制机制有重要的理论价值，还将为农业生产中水稻株型改良提供理论依据，为水稻高产育种作出贡献。

水稻株型和粒型是影响其产量的主要因素，然而，影响这些农艺性状的分子机理，目前还不十分清楚。通过基因工程技术，我们得到一个水稻分蘖和粒型改变突变体，经典遗传研究表明该性状由一对隐性核基因控制（原始命名为RTD1，现改为SHG1）。通过图位克隆的方法，我们构建了shg1突变体的高饱合的遗传图谱和精细物理图谱并鉴定突变座位及其等位基因，研究鉴定该基因功能及其调控机制。实验结果表明，SHG1编码一个Kinesin蛋白，参与调控细胞骨架形成，并最终影响细胞伸长。在shg1突变体中，由于SHG1基因的功能丧失，BR信号转导途径受损，多个BR信号途径基因表达发生改变，从而导致细胞伸长受阻。此外，SHG1基因受auxin诱导表达，而且ARFs可以与SHG1启动子结合，激活SHG1基因表达。这一基因克隆，将为理解BR和auxin协同调控株高粒型分子机理奠定坚实基础，也为指导育种实践，培育高产水稻品种具有重要指导意义。