杨树光敏色素互作因子4 (Phytochrome Interacting Factor 4, PIF4) 调控植物生长与季节性休眠的分子机理研究

Survival of trees growing in temperate zones requires a cycling between active growth and dormancy. Recently, genetic and molecular approaches have revealed a remarkable conservation of the genetic pathways regulating seasonal dormacy in Populus and the pathways controlling flowering time in Arabidopsis. However, it is only the tips of the iceberg referring to understanding the molecular mechanism of seasonal growth in perennial trees. PHYTOCHROME INTERACTING FACTOR 4 (PIF4) has been well characterized in annual plants. It functions as a hub by connecting the multiple external and internal signals to plant growth, such as light, temperature, hormone and the circadian clock in Arabidopsis. Since phytochrome genes has been showed to play important roles in seasonal dormancy in Populus, PIF4 orthologs is thought to be one of the strongest candidates that involves in seasonal dormancy in trees. In this project, we plan to investigate the function of PIF4 orthologs in hybrid aspen, including their functions in tree’s basic growth regulation and in short-day induced seasonal dormancy.

为了适应恶劣的气候环境，温带多年生木本植株进化出了季节性生长与休眠的适应机制。近几年研究发现，控制木本植物季节性休眠的基因调控网络与拟南芥中控制开花的光周期基因调控网络有着很高的保守型。然而，人们对木本植物季节性休眠的分子机制认识还只是冰山一角。在一年生植物中，光敏色素互作因子4（PIF4）的功能在拟南芥中已被广泛研究。PIF4是介导外界环境如光照，温度及内源因子如激素，节律钟等与植物生长的关键调控因子。而在多年生木本植物中，已有的报道证明光敏色素是调控木本植物季节性休眠的重要因子。作为光敏色素的直接下游调控基因，木本植物中PIF4的同源基因是我们研究木本植物季节性休眠分子机理的重要候选基因。本研究中，申请人拟以杨树为研究对象，深入研究杨树中PIF4同源基因在控制植物生长与季节性休眠的分子机制。

为了抵御严冬，温带多年生木本植株进化出了季节性生长与休眠的适应机制。研究发现树木的季节性生长停止和休眠开始的时间主要受光敏色素（PHY）信号感知的光周期调节。然而，关于PHYs如何感知光信号来介导生长休眠变化的分子网络还知之甚少。本项目中，我们研究了PHYB基因及其下游光敏色素相互作用因子（PIF）在杂交白杨树庇荫反应和季节生长调节中的功能。我们发现PHYB是树木季节性生长的促进因子。PIF4和PIF8位于PHYB下游共同调控植物的庇荫反应。但只有PIF8在抑制季节性增长方面起主要作用。总之，本研究揭示了杨树中PHYB-PIF4/PIF8调节子协调调节SAS反应和树木的季节性生长停止的分子调控网络。