Structure-Function Studies on Phytochrome

光敏色素的结构-功能研究：光敏色素对光的感知启动了绿色植物的许多发育和生理反应。这项研究将为高等植物和绿藻的光敏色素结构和由光敏色素光激活启动的初级信号转导过程提供新的信息。对这两种光敏色素的研究将包括a)描绘光诱导蛋白质部分构象变化的区域，b)高等植物和藻类光敏色素之间一级结构保守区域的特征，以及c)阐明使纯化的光敏受体具有异质性的结构特征。关于光敏色素在植物细胞中的主要功能，光敏色素是一种蛋白激酶或在功能上与一种蛋白激酶相关的假设将受到检验。这些研究将包括a)描绘与光敏色素结合的ATP(或其他核苷酸)的位置和化学计量，b)证明该激酶是否与光敏色素共纯化，以及c)在体内和体外确定光敏色素光激活是否改变内源或外源底物的蛋白质磷酸化。“光敏色素相关”蛋白激酶的体内和体外底物将进行比较。光敏色素对环境的光感知是植物最适生长发育所必需的。在自然环境中，植物暴露在极端的光照强度和光谱质量下。光敏色素作为这种变化的分子传感器，通过基因表达的变化来调节植物的发育状态(参见。诱导种子萌发或开花)以及影响生长速率或叶绿体取向，以优化光合作用的光捕获。这项建议中概述的实验将提供关于光敏色素结构和光敏色素光激活启动的信号转导组件的新信息。预计在分子水平上理解光敏色素介导的信号转导过程将促进利用分子遗传和生化工具提高植物生产力的新方法。

Structure-Function Studies on Phytochrome: Light perception by phytochrome initiates many developmental and physiological responses in green plants. Research outlined in this proposal will provide new information regarding both phytochrome structure and the primary signal transduction process(es) initiated by phytochrome photoactivation in both a higher plant and a green alga. Studies on both phytochromes will include a) delineation of regions of light-induced conformational changes in the protein moiety, b) characterization of conserved regions of primary structure between the higher plant and algal phytochromes and c) elucidation of structural features which confer heterogeneity to the purified photoreceptor. With regard to the primary function of phytochrome in plant cells, the hypothesis that phytochrome is a protein kinase or is functionally associated with a protein kinase, will be tested. These studies will include a) delineation of the sites and stoichiometry of ATP (or other nucleotide) binding on phytochrome, b) demonstration whether the kinase co-purifies with phytochrome and c) determination whether phytochrome photoactivation alters protein phosphorylation of endogenous or exogenous substrates both in vivo and in vitro. In vivo and in vitro substrates for the "phytochrome-associated" protein kinase will be compared. Environmental photoperception by phytochrome is essential to optimal growth and development of plants. In the natural environment, plants are exposed to extremes in light intensity and spectral quality. Phytochrome serves as a molecular sensor of such changes by modulating the state of development of the plant via changes in gene expression (cf. induction of seed germination or flowering) as well as influencing growth rate or chloroplast orientation to optimize light capture for photosynthesis. The experiments outlined in this proposal will provide new information regarding both phytochrome structure and the components of the signal transduction initiated by phytochrome photoactivation. It is anticipated that an understanding of the phytochrome-mediated signal transduction process at a molecular level will foster new approaches to improve plant productivity using molecular genetic and biochemical tools.