水稻籼粳杂种优势利用能进一步提高水稻产量，但株高超亲易倒伏等不良性状限制了其广泛应用。近年，对水稻籼粳杂种优势的机制已从基因组、转录组、表观遗传修饰等不同的领域进行了研究，但是针对籼粳间杂交种株高超亲现象的分子机制研究相对滞后。本项目首先从不同的籼粳杂交组合入手，通过轮回选育获得不同株高显著超亲的近等基因系，配制定位群体图位克隆相关基因，并对克隆的基因进行遗传转化验证；利用转录水平和蛋白水平分析及表观遗传修饰等方法研究产生株高超亲现象的分子机理。其次，利用CRISPR-Cas9系统敲除或弱化克隆基因的功能，配制杂交组合进一步验证其降秆效应。同时，选择一些生产上应用但株高偏高的品种，通过基因敲除或功能弱化进行品种的局部改良。最后，通过对获得结果的系统分析，期望能揭示籼粳株高超亲优势的机制，并为育种实践提供理论指导。

Stronger heterosis in indica/japonica hybrids can be used to further increase rice yield in breeding programs. However, there exist factors limiting wider application of the hybrid vigor, including the elevated plant height that often causes lodging problem. Although studies on molecular mechanisms of heterosis by employing whole genome sequencing, RNA-seq and epigenetic approaches have been well documented, attention to plant height heterosis has not been given comparably. In this proposal, we will develop taller-than-parent near isogenic lines (NILs) from indica/japonica hybrids and then clone gene(s) related to plant height heterosis. The cloned gene(s) will be extensively characterized at transcript and protein level, combined with epigenetic analysis, to elucidate mechanisms determining the plant height vigor. The CRISPR-Cas9 system will be used to knock out or weaken the function of the cloned gene(s) in japonica varieties, and the mutated varieties are crossed to indica varieties to examine their effectiveness in controlling plant height of the hybrids. In addition, commercial varieties with under-desired plant height are going to be improved by editing the plant height gene(s). The outcomes from this proposal are expected not only to shed light on understanding mechanisms of heterosis but also to provide basis for plant height control in molecular breeding of rice.