基于新转录因子功能研究解析植物光调控基因表达网络的全景

Blue light sensing cryptochromes (CRYs) and red/far-red sensing phytochromes (PHYs) are two major photoreceptors that regulate important growth and developmental process throughout plant life cycle. Both CRYs and PHYs regulates the intricate gene expression network to mediate plant light responses via two core pathways: CONSTITUTIVE PHOTOMORPHOGENIC1 (COP1)/SUPPRESSOR OF PHYA-105 (SPA) pathway and PHYTOCHROME INTERACTING FACTOR (PIF) pathway. However, these core regulatory mechanisms do not fully explain the light regulated gene expression network. The other internal factors such as circadian clock, phytohormone and other signal modify the photoreceptor-regulated transcriptional network to fine-tune the plant fitness to the light environment. Recently, the applicant identified the novel transcription factors, SIL1 (SHORT IN LIGHT 1) and SIL2, that enhance the light responses on the seed germination and the de-etiolation. The expression of SIL1/2 is developmentally programmed. SIL1/2 are expressed only in the imbibed seed and early seedling stage. Therefore, it is hypothesized that SIL1/2 closely coordinate with core light signaling pathways to enhance CRY and PHY signal transduction mechanism during these developmental stages. In this study, the mechanism underlying the SIL1/2 promotion of light signaling pathways and the transcriptional regulation of SIL1/2 will be analyzed to understand how developmental signal enhances cellular light sensitivity during seed-to-early seedling stage via the regulated expression of SIL1/2. In addition, novel transcription factors involved in light signal transduction mechanism will be also identified in this study. For this purpose, a new gene discovery system, in which 400 transcription factors are easily analyzed in Marchantia, a primitive land plant recently highlighted as a simple genetic tool, will be developed and applied to the screening for the transcription factors involved in light signal transduction mechanism. The function of identified transcription factors will be tested in both Marchantia and Arabidopsis. These analysis will uncover the molecular mechanism underlying intricate light regulated gene expression network in land plants.

隐花色素（CRY）和光敏色素（PHY）介导的光信号在植物生长发育过程中发挥关键作用。CRYs和PHYs通过以COP1/SPA和PIFs途径为主的核心信号途径调控植物的光形态建成。但是其他的内部信号，如节律、激素和发育信号或者外部信号通过改变光受体调控的基因表达网络来调整植物的光响应的分子机制尚不明确。本项目前期研究中，申请者在拟南芥中鉴定出连接发育信号和光信号的新转录因子—SIL1/2，但是，SIL1/2在CRY和PHY信号转导机制中的功能尚不清楚。故本项目将解析拟南芥发育信号通过调整SIL1/2的表达增强植物细胞的光敏感的分子机制。进一步，本项目将以Marchantia为遗传工具，筛选和鉴定其他受内外因子所调控，改变光调控网络的新转录因子，全面解析光信号调控基因表达网络下的复杂分子机制，揭示CRY和PHY所介导的光响应的全景，为改良作物生长发育特性，增加作物产量奠定基础。

CRY和PHY所调控的光响应基因表达网络的核心机制已被鉴定，但是其他的内部信号，如节律、激素和发育信号或者外部信号通过改变光受体调控的基因表达网络来调整植物的光响应的分子机制尚不明确。本项目鉴定出连接植物早期的发育信号和光信号的转录因子—SIL1/2，并阐明SIL1/2参与红光信号转导途径，受到光敏色素phyB的调控，并通过调控GA信号通路中的部分相关基因的表达来调控种子的休眠和萌发。本项目在阐明新的转录因子参与光信号转导途径的同时，不仅丰富了光调控的基因表达网络，揭示了生长发育信号和激素信号通过改变光受体调控的基因表达网络来调控植物的生长发育过程，也能为通过控制光信号来提高作物产量而改良作物生长发育特性提供依据，开发有利的工具。