转录因子STO/BBX24参与植物UV-B信号转导的分子调控机制

The stratospheric ozone layer protects all living organisms on the earth from solar ultraviolet radiation. Due to ozone depletion in the past several decades, enhanced UV-B radiation has been a major world-wide concern among the public and scientists. Enhanced UV-B in solar radiation initiates expression changes of many important genes, and leads to a series of metabolic and morphological responses. The photoreceptor UVR8 (UV RESISTANCE LOCUS8) for sensing the solar UV-B radiation has been identified in the past few years. In our previous research, it was proved that the gene STO (SALT TOLERANCE)/BBX24 (B-box24) acted as a negative regulator in the UV-B signaling in Arabidopsis. In this proposed study, the sto mutant, 35S::STO-GFP overexpression line and the wild type Arabidopsis thaliana (Col-0) will be used to investigate the molecular mechanism for the STO mediated UV-B signaling. The specific monoclonal antibodies (anti-STO) with high affinity will be developed by means of molecular immunological techniques. The targeted DNA sequences of the transcription factor STO and its physiological interactive proteins will be identified respectively by ChIP and CoIP. The candidate genes’ transgenic plants then will be constructed to investigate their functions and interactions with proteins UVR8, STO, COP1 and HY5 respectively under UV-B radiation. Moreover, the key binding sites of the STO promoter that is required for the UV-B response will be identified. The interactions among the STO-targeted-genes, STO-interacting-proteins as well as other investigated components in the UV-B signaling pathway will be analyzed. The project will provide new evidences for further understanding the molecular regulation mechanism of the transcriptional activation of STO in response to UV-B radiation.

大气臭氧层耗损引起地面UV-B辐射增强对植物、动物和人类以至整个地球生态系统的影响，已成为国际社会高度关注的重大科学问题。太阳辐射中UV-B组分的增强对植物的形态建成、生长、发育和代谢产生重要的影响，近年来的研究已成功鉴定出植物UV-B光受体是UVR8。本课题组前期研究已经证实STO/BBX24是UV-B信号途径的负调控因子。本项目在此研究基础上，以野生型拟南芥、sto突变体和35S::STO-GFP超表达体为材料，利用分子免疫学技术，制备高亲和力单克隆anti-STO抗体，通过ChIP-Seq 和CoIP技术筛选STO的互作分子（与STO结合的靶序列DNA和靶蛋白），构建候选互作分子的转基因植株，验证候选互作分子在UV-B辐射下的功能；鉴定STO启动子的关键结合位点，进而分析靶序列DNA和靶蛋白与UV-B信号通路中重要元件的相互作用关系，阐明STO参与UV-B信号通路的分子调控机制。

UV-B作为一种重要的外界信号调控植物的光形态建成，对植物的生长、发育和代谢都有重要的调节作用。UV-B信号转导途径是近年来植物光生物研究领域的热点，本实验室的前期研究结果证实转录因子STO是UV-B信号途径中的负调控因子，然而转录因子STO参与UV-B信号转导的分子调控机制并不清楚。本项目通过分子免疫学、细胞生物学、蛋白质组学及分子遗传学方法研究STO蛋白参与UV-B信号转导的分子调控机制，发现STO可与HY5启动子结合，但STO促进HY5基因表达的能力相比HY5促进自身表达显得很弱；STO突变后，与花青素生物合成相关的MYB–bHLH–WD40 (MBW)蛋白明显增加，受HY5调控的花青素代谢相关蛋白也明显上调；同时可能由于反馈调节作用使得催化花青苷合成所需的关键酶UFGT表达下调；另外，与光合作用相关蛋白也下调。基于以上结果，我们推测STO在UV-B辐射下与HY5竞争HY5的启动子介导花青素积累，同时花青素的合成代谢与光合基因上调有关。本项目通过分析调控STO的转录调控机制，以期能够更深入了解UV-B促进花色素苷合成的分子机理，为分子育种提供新的基因资源，具有重要的意义。