Initial Events in Photoreceptor Signaling

描述（由申请人提供）：光信号是植物许多发育过程的诱导和调控所必需的。遗传分析表明，光反应不仅仅是线性信号转导途径的终点，而是来自各种光感受器系统的信号整合的结果。光敏色素是红/远红光吸收受体，已被证明是光调节丝氨酸/苏氨酸激酶。光敏色素的亚细胞位置受光调节，在黑暗中处于细胞质中，在光中输入到离散的核位点。遗传和分子分析已经确定了在细胞质和核室中光敏色素下游的许多蛋白质，然而传统的遗传筛选并没有确定调控回路的所有组成部分。此外，许多机械细节根本不为人所知。建议使用分子，生化和遗传策略来识别和表征在光敏色素信号转导途径中起作用的信号转导成分。这些研究的主要目的是：(1)确定细胞质磷酸化蛋白PKS1在胞浆内保留光敏色素B的机制；(2)鉴定光敏色素B定位到亚核库的相关蛋白；(3)表征遗传筛选中发现的PHY信号通路中的新成分；(4)评估响应光的蛋白质运输水平。总之，所提出的实验将进一步加深我们对光敏色素介导的信号转导途径的认识，并将解决光敏色素通过传递光信号来调节基因表达、细胞扩增和分裂以及叶绿体发育等多种反应的机制。长期目标是完全了解植物感知和响应局部光环境的信号转导网络，并将其与其他生物信号转导的一般机制联系起来。

DESCRIPTION (provided by applicant): Light signals are required for the induction and regulation of many developmental processes in plants. Genetic analysis demonstrates that light responses are not simply endpoints of linear signal transduction pathways, but are the result of the integration of signals from a variety of photoreceptor systems. The phytochromes are red/far-red light absorbing receptors that have been shown to be light-regulated serine/threonine kinases. The subcellular location of phytochromes is regulated by light, being cytoplasmic in the dark, and imported to discrete nuclear sites in the light. Genetic and molecular analyses have identified a number of proteins that act downstream from phytochromes, in both the cytoplasmic and nuclear compartments, however traditional genetic screens have not identified all the components of the regulatory circuitry. Moreover, many mechanistic details are simply not known. It is proposed to use molecular, biochemical and genetic strategies to identify and characterize signal transduction components that act early in phytochrome signal transduction pathways. The primary aims of these studies are (1) to determine the mechanism of cytosolic retention of phytochrome B by PKS1, a cytoplasmic phosphoprotein; (2) to identify proteins involved in phytochrome B localization to subnuclear pool; (3) to characterize new components in the PHY signaling pathways identified in genetic screens; and (4) to assess the level of protein trafficking in response to light. In summary, the proposed experiments will further our knowledge of phytochrome-mediated signal transduction pathways, and will address the mechanism by which phytochromes transmit light signals to regulate such diverse responses as changes in gene expression, cell expansion and division, and chloroplast development. The long-term objective is to completely understand the signal transduction networks that allow plants to perceive and respond to their local light environment, and to relate this to general mechanisms of signal transduction in other organisms.