根是植物吸收土壤中水分和养分、固定植株、影响植物生长和产量潜力的主要营养器官。冠根是水稻根系的主要组成部分，其数目决定了水稻对土壤水分和养分的吸收利用效率。目前，冠根形成的分子机理尚不清晰。本项目拟利用水稻染色体片段代换系及其衍生群体，采用图位克隆的方法分离克隆一个影响水稻冠根数的基因（CRN），通过遗传学、生理学和分子生物学等技术手段，研究其生物学功能。在表达水平和蛋白水平上分析和验证CRN的互作基因，剖析其参与的分子调控网络。利用水稻核心种质测序及关联分析，鉴定CRN自然发生的等位变异及其对水分和养分(如氮、磷)吸收利用的影响，发掘优异等位基因。预期研究结果将有利于更好地了解水稻根系形成的分子调控机理，为培育水分和养分高效利用的水稻新品种奠定理论和实践基础。

Roots are essential organs for exploiting soil resources such as water and mineral nutrients, and supporting plant growth as well as crop productivity. The rice root system is mainly composed of postembryonic shoot-borne roots termed crown roots, and its numbers play the crucial role in capturing water and mineral nutrients. However, the molecular mechanism of crown root formation in rice remains unclear. The project is proposed to map-based clone a gene for crown root number (CRN) by using the segregation population derived from chromosomal substitution segment lines in rice, and to analyze its biological functions with the integrated approaches in genetics, physiology and molecular biology. Other main activities proposed in this project also include identification and validation of gene regulatory network and signaling pathways that the CRN gene involved in controlling crown root formation, and mining of the natural occurring alleles with its functions in use-efficiency of water and nutrients (such as nitrogen and phosphate) through association mapping with the core collection of rice germplasm. These results will facilitate better understanding of the molecular mechanism of root formation and root architecture in rice, and establish a practical and theoretical foundation for improving water and nutrient use-efficient rice varieties.