MOLECULAR MECHANISMS OF PHYTOCHROME SIGNALING

项目描述（由申请人提供）：该项目名为“光敏色素信号的分子机制”（PI J. Clark Lagarias, UC Davis），主要研究光敏色素家族蛋白光传感器的基础知识。光敏色素利用线性四吡啶作为发色团来感知光的质量、数量和持续时间。光化学光感应触发构象变化，通过调节下游转录级联的靶分子调节生命系统的行为。提出的研究解决了这样一个假设，即光传感的基本机制在整个数十亿年的进化中一直保持保守，因为真核宿主捕获了蓝细菌的内共生。主要研究方向有三个：植物和蓝藻光敏色素的光转化和蛋白-发色团相互作用；植物光敏色素的进化机制；陆地植物光敏色素的光转化和信号转导活性。通过研究从蓝藻到植物等进化上遥远的物种的光敏色素，我们的研究试图阐明光感的基础和用于控制基因表达的分子内结构变化。来自蓝藻、绿藻小单胞菌和陆地植物拟南芥和小麦的光敏色素将被用来检验光调节构象变化触发所有现存真核光敏色素向核易位的假设。为了验证这些假设，我们利用计算分析来指导实验设计，利用蛋白质生物化学和分子生物学来表达和纯化光感受器，利用酶学和光谱学来了解光诱导的光感受器结构变化，以及对模式陆地植物拟南芥核易位和功能的体内评估。的意义。对光敏色素的研究提供了关于生命系统如何调节其行为以响应外部环境的基础知识。光敏色素是触发种子萌发、启动幼苗早期发育和诱导开花（性发育）的关键调控因子。由于光敏色素在阴感中的作用，在现代农业中，光敏色素是高密度作物产量的重要限制因素。应用我们的见解

DESCRIPTION (provided by applicant): This project, entitled "Molecular Mechanisms of Phytochrome Signaling" (PI J. Clark Lagarias, UC Davis), focuses on gaining fundamental knowledge about the phytochrome family of protein light sensors. Phytochromes utilize linear tetrapyrroles (bilins) as chromophores to sense light quality, quantity and duration. Photochemical light sensing triggers conformational changes that modulate the behavior of living systems via target molecules that regulate downstream transcriptional cascades. The proposed investigations address the hypothesis that the fundamental mechanism of light sensing has remained conserved throughout billions of years of evolution since endosymbiotic capture of a cyanobacterium by a eukaryotic host. There are three specific aims focused on conservation of photoconversion and protein-chromophore interactions in plant and cyanobacterial phytochromes, the evolutionary genesis of plant phytochrome, and phytochrome photoconversion and signaling activity in land plants. By examining phytochromes from evolutionarily distant species ranging from cyanobacteria to plants, our studies seek to elucidate the basis of light sensing and the intramolecular structural changes that are used to control gene expression. Phytochromes from the glaucophyte Cyanophora paradoxa, the chlorophyte Micromonas pusilla, and the land plants Arabidopsis thaliana and Triticum aestivum (wheat), will be used to examine the hypothesis that light-regulated conformational change triggers translocation to the nucleus in all extant eukaryotic phytochromes. To test these hypotheses, we leverage computational analyses to guide experimental design, protein biochemistry and molecular biology to express and purify photoreceptors, enzymology and spectroscopy to understand light-induced changes in photoreceptor structure, and in vivo assessment of nuclear translocation and function in the model land plant Arabidopsis thaliana. Significance. Studies on phytochromes provide fundamental knowledge about how living systems regulate their behavior in response to the external environment. Phytochromes are key regulators for triggering seed germination, initiating early development of the seedling, and inducing flowering (sexual development). Because of their role in shade sensing, phytochromes are an important limiting factor for yield at high crop densities in modern agriculture. Application of the insights from our studies can improve nutrition, enhancing health, lengthening life, and reducing the burdens of illness and disability. Moreover, photosensory proteins are valuable tools for studying function and localization of mammalian proteins (optogenetics), and this work yields new tools for fundamental research into such systems.