水稻分蘖角度调控基因TAC9的克隆与功能研究

Tiller angle is one of the important components determining the plant architecture in rice, thus having been long considered as an important agronomic trait related to grain yield. Many QTLs associated with tiller angle control have been mapped in recent years and some genes have been cloned, such as TAC1, PROG1、LPA1、LAZY1; however, the molecular mechanism involved in tiller angle control is still unclear at large. In this study, we plan to characterize TAC9, a tiller angle gene that has been identified by map-based cloning in our lab. We will perform detailed functional analyses on TAC9, investigate its possible participation in auxin signaling and gravitropism, and explore the molecular network of tiller angle control by transcriptome sequencing and co-immunoprecipitation-mass spectrometry. A set of CRISPR-Cas9 constructs will be designed and transformed to a commercial variety to create allelic mutations. Finally, we want to understand how the expression level change or artificially weakened function of TAC9 affects tiller angle, aiming to provide suggestive information for precisely improving plant architecture by molecular breeding.

分蘖角度是水稻株型的主要构成因素之一，是水稻的重要农艺性状，与水稻株型结构和产量直接相关。尽管近年来定位了诸多与分蘖角度相关的QTLs，并克隆了TAC1、PROG1、LPA1、LAZY1等调控水稻分蘖角度的重要基因，但目前人们对调控水稻分蘖角度的分子机制还知之甚少。本研究将以前期图位克隆获得的水稻分蘖角度相关基因TAC9为切入点开展研究，验证该基因的功能；分析TAC9基因与生长素、重力反应的关系；并结合转录组测序和免疫共沉淀-质谱检测技术初步探讨TAC9基因的分子作用网络；最后利用CRISPR-Cas9基因编辑技术进行多位点编辑创制系列突变体，以明了该基因的表达水平和功能的强弱与分蘖角度变化的关系，从而为理想株型的分子育种提供理论指导。

分蘖角度是影响水稻株型的重要性状之一，它直接影响了水稻的种植密度、光合效率等农艺性状，进而影响水稻产量和品质。尽管近年有诸多调控水稻分蘖角度的基因被相继报道，但目前人们对水稻分蘖角度调控机制还知之甚少。本研究以株型松散度不同的籼稻和粳稻杂交再经过多轮回交后创制极紧凑的近等基因系，利用近等基因系自交的F2定位群体克隆到TAC9基因。通过遗传转化证实TAC9基因是调控水稻分蘖角度的关键基因。并且研究发现TAC9基因在水稻分蘖基部表达量较高，定位在细胞膜和细胞核上，动态调控了水稻的分蘖角度。通过芽胚的重力反应实验证明TAC9影响水稻地上部分重力响应，TAC9的过表达减弱了胚芽对重力的反应。进一步利用生长素应答基因作为标记基因检测发现TAC9还影响了水稻基部生长素的不均等分布，从而最终影响了水稻的分蘖角度。此外还利用 CRISPR/Cas9 基因编辑技术，对株型松散的水稻品种 9311 和南京11的 TAC9基因进行编辑，获得不同梯度的分蘖角度水稻材料。本研究为水稻株型育种提供了一定的理论指导。