BBX4调控拟南芥幼苗光形态建成的机制研究

Photomorphogenesis is a key process during plant development, occurring when a germinating seedling emerges from darkness into light, which is crucial for the survival of seedlings. BBX proteins are a class of zinc-finger transcription factors that contain one or two B-box domains. Some members in this family are regulators of plant photomorphogenesis. BBX4 is a positive regulator of light signaling as the bbx4 mutant shows elongated hypocotyl compared to its wild-type in the light. Our previous study showed that the BBX4 protein had a low abundance in dark-grown seedlings, whereas it accumulated rapidly after those seedlings were transferred into the light. We also found that BBX4 interacted with the red-light receptor PHYB and a negative regulator in the light signaling, PIF3. In this project, we will generate materials of BBX4 and its interacting protein genes, to reveal the physiological and biochemical mechanism underlying their interactions and identify the downstream genes regulated by BBX4, thereby further dissect the molecular mechanism of the regulation of photomorphogenesis by BBX4 protein during dark to light. Results are expected to facilitate the study of light-regulated plant growth and development and provide gene resources for optimizing agricultural production.

植物幼苗光形态建成是种子萌发后从黑暗环境转至光照条件下的必要发育过程，对幼苗的出土存活率至关重要。BBX蛋白是一类含有B-box结构的锌指蛋白转录因子，其家族成员参与调控幼苗光形态建成。BBX4是其中一个光信号正调控子，光下生长的拟南芥bbx4突变体幼苗具有显著伸长的下胚轴。本项目前期研究发现在暗下生长的拟南芥幼苗中BBX4蛋白水平极低，转至光下后蛋白水平迅速升高，同时发现BBX4与红光受体PHYB及光信号负调控子PIF3互作。因此拟通过构建BBX4与其互作蛋白基因的遗传材料，分析BBX4与PHYB、PIF3以及COP1互作的生理生化机制，同时鉴定受BBX4调控的下游光信号转导基因，进而解析黑暗及光照环境通过调控BBX4蛋白水平及活性来调控植物幼苗光形态建成的作用机制。预期结果将有助于了解光信号调控植物生长发育的基本规律，并为提高植物幼苗出土存活率，优化农业生产提供基因资源。

光是影响植物生长发育的重要因素。红光受体PHYB吸收红光信号后，在植物细胞中引发一系列分子事件促进幼苗光形态建成。本研究中，我们发现PHYB直接与红光信号正调节因子BBX4相互作用，促进红光下BBX4在植物幼苗中的积累。红光下积累的BBX4与红光信号负调节因子PIF3相互作用，抑制PIF3蛋白转录激活活性及其下游基因的表达。在黑暗中，BBX4依赖于COP1和26S蛋白酶体系统发生降解。因此，BBX4是PHYB-PIF3介导的光信号调控模块的关键组成部分，精细调控植物幼苗对红光信号的响应。PHYB促进BBX4在红光下的积累，BBX4通过互作抑制PIF3的转录激活活性，进而促进植物幼苗光形态建成。项目结果有助于理解光信号对植物生长发育的调控机制，提高植物幼苗出土存活率，优化农业生产。