多倍体进化过程中棉花幼苗下胚轴向光弯曲的调控机制解析

单侧蓝光诱导的下胚轴向光弯曲，有助于优化幼苗的生长取向，以获得合适的光捕获，对幼苗的破土和形态建成意义重大。该反应由向光素介导的信号途径所调控，但由于蓝光受体的功能冗余性和不同植物的特异性，该信号途径细节仍存在很多未知，尤其是在多倍体作物中，不同品种（尤其是二倍体种和多倍体种）对蓝光的响应机制、在多倍体进化中的选择机制仍不清楚。本项目聚焦棉花这一重要经济作物，前期研究发现单侧蓝光可诱导不同棉种产生差异向光弯曲表型，棉花下胚轴向光弯曲可能主要受D亚基因组基因控制，DNA甲基化对该过程基因偏好表达起重要作用。在此基础上，本项目拟综合多种技术手段，探究三个棉种差异响应不同光照的生理学、细胞学基础，解析多倍体进化过程中不同棉种向光性差异的调控机制，并克隆陆地棉下胚轴向光弯曲核心调控基因，评估其生产潜力，从而为棉花幼苗光适应和光能高效利用提供新的视野，为棉花生产和育种提供理论指导和基因资源。

Blue light-induced hypocotyl phototropism plays a critical role in seedling morphogenesis via optimizing their growth orientation and facilitating the proper light capture. This adaptive response is fine-tuned by the phototropins-mediated signaling pathway. However, the regulatory mechanism of hypocotyl phototropism remains far from fully understood due to the redundancy of blue light receptors and the specificity among different species. Especially in polyploid crops like cotton, the blue light-response characteristics between diploid and tetraploid species, and the selection signatures during cotton domestication remain obscure. Previously, the applicant investigated the seedling phenotype of three cotton species (Gossypium hirsutum, G. arboretum, and G. raimondii) exposed to single-direction light of different qualities, and found that blue light, the key inducer of the phototropism, can lead to differential hypocotyl bending among three species. The follow-up transcriptomic and DNA-methylomic analysis revealed that the hypocotyl bending in G. hirsutum is mainly controlled by blue light responsible genes from Dt sub-genome originating from G. raimondii. In this project, the applicant will focus on the hypocotyl phototropism in cotton, and explore the underlying mechanism about how the distinct light-response raise up during diploid-to-tetraploid evolution. Moreover, the applicant will clone several key regulatory genes from G. hirsutum, evaluated their applicant potential, and construct the multi-genes modulatory networks. This project will provide new insights into the adaptation and efficient utilization of light in cotton seedlings, thus guiding cotton breeding and cultivation.