Uncovering HEMERA-mediated Phytochrome Signaling Mechanisms in Arabidopsis

光是最具影响力的环境信号之一，几乎调节植物生长和发育的各个方面，从种子萌发、叶绿体分化和光合作用到开花。 虽然它已经是众所周知的，光敏色素是红色和远红光受体介导的大部分的光响应，早期信号转导机制连接光敏色素的光激活和由此产生的形态反应仍然难以捉摸。PI开发了一种新的遗传筛选，专门针对参与最早的光反应之一的信号成分，即细胞内光敏色素的运动。这种独特的遗传筛选鉴定了植物模式物种拟南芥中光敏色素信号传导的新组分HEMERA（HMR）。有趣的是，HMR是多种早期光敏色素信号事件所必需的，并且是叶绿体从其前质体前体发育（叶绿体分化）所必需的第一个光敏色素信号组分。该研究旨在揭示HMR介导的导致光依赖性叶绿体分化的信号机制。具体目标是：（1）确定光敏色素如何调节HMR;（2）确定HMR在细胞中与光信号传导和叶绿体分化的关系;（3）通过寻找恢复植物正常性状的突变来鉴定和表征HMR下游的组分，其中HMI在其他方面不起作用。这个项目的结果可能会大大有助于我们的基本知识，植物的发展是如何调节环境线索。更好地理解这一过程将对提高作物产量和增强作物农艺性状具有深远的意义。特别是，阐明叶绿体分化是如何启动的光将最终提供的知识，以促进科学家提高生物燃料作物的光合能力。此外，该项目将为博士后研究员、研究生和本科生提供分子遗传学方法方面的优秀培训。

Light is one of the most influential environmental cues regulating almost every facet of plant growth and development, from seed germination, chloroplast differentiation and photosynthesis, to flowering. Although it has been well known that phytochromes are red and far-red light receptors mediating most of the light responses, early signaling mechanisms linking light activation of phytochromes and the resulting morphological responses remain elusive. The PI developed a novel genetic screen specifically targeted at signaling components involved in one of the earliest light responses, the movement of phytochromes within the cell. This unique genetic screen identified a novel component for phytochrome signaling, HEMERA (HMR), in the plant model species Arabidopsis. Interestingly, HMR is required for multiple early phytochrome signaling events and is the first phytochrome-signaling component essential for the development of chloroplasts from their pro-plastid precursors (chloroplast differentiation). The research is aimed at uncovering HMR-mediated signaling mechanisms leading to light-dependent chloroplast differentiation. The specific aims are: (1) To determine how phytochromes regulate HMR; (2) To determine the location of HMR in cells in relationship to light signaling and chloroplast differentiation; (3) To identify and characterize components downstream of HMR by looking for mutations that restore normal traits in a plant where HMI is otherwise not functional. The outcomes of this project could contribute significantly to our basic knowledge of how plant development is regulated by environmental cues. A better understanding of this process will have profound implications in increasing yield and enhancing agronomically beneficial traits in crops. In particular, the elucidation of how chloroplast differentiation is initiated by light will ultimately provide the knowledge to facilitate scientists to improve photosynthetic capacity in biofuel crops. In addition, the project will provide excellent training in molecular genetic approaches for postdoctoral fellows, graduate students, and undergraduate students.