在出土过程中，植物幼苗需根据土壤环境调控自身形态建成实现破土而出。在土壤中，幼苗顶端形成弯钩以减少土壤机械损伤，保护顶端分生组织。破土而出后，光诱导顶端弯钩打开，及时启动光形态建成，但是，光调控幼苗顶端弯钩打开的信号通路尚未清楚。我们的初步结果显示红光受体phyB与顶端弯钩形成关键蛋白HLS1直接互作且在光打开顶端弯钩过程中具有重要作用。本课题将深入分析phyB和HLS1的遗传关系以及蛋白相互作用的特点。探究红光对HLS1转录和转录后调控作用，阐明红光调控HLS1基因表达和蛋白质活性的分子机制与生化基础。最后，定量分析不同光照条件下顶端弯钩打开的动力学特征，结合HLS1上游多层次调控方式的数据，利用系统生物学建立光调控顶端弯钩打开的数学模型。本课题将首次揭示红光受体直接调控蛋白质活性的全新作用机制，系统阐述光调控出土幼苗顶端弯钩打开的分子信号网络，为农业中提高幼苗出土存活能力提供理论基础。

In order to successfully emerge from soil, seedlings must regulate their growth and developmental morphogenesis in adaption to ambient soil environment. In the soil, the seedlings adopt apical hook curvature to avoid soil mechanical stress damage, protecting the fragile apical meristem. After growing out of soil, light rapidly induces the hook opening and initiate photomorphogenesis. However, the molecular mechanism how light regulates hook opening is largely unknown. Our preliminary data have shown that the red light photoreceptor phyB and the master factor in hook development HLS1 protein interact with each other and also play important roles in light-induced hook opening. In this proposal, we will examine the genetic relationship and characterize the protein interactions between phyB and HLS1. Then we will investigate the transcriptional and post-transcriptional regulations of HLS1 by light, and we will further elucidate the molecular and biochemical mechanism under how light regulate HLS1 gene expression and protein activities. Moreover, the kinetics of hook opening upon various light conditions will be quantitatively analyzed. We will combine the data of multi-leveled regulations of HLS1 and build the mathematical model of light-induced hook opening. Taken together, this study will reveal the novel actions of which the red light photoreceptor directly regulates target protein activity, and comprehensively demonstrate the signal transduction networks of light-induced hook opening upon soil emergence, providing the theoretical basis for improving the seedling soil emergence ability in the agricultural industry.