MOLECULAR MECHANISMS OF PHYTOCHROME SIGNALING

描述(由申请人提供)：该项目名为“光敏色素信号的分子机制”(加州大学戴维斯分校PiJ.Clark Lagarias)，重点是获得有关光敏色素蛋白质光传感器家族的基本知识。光敏色素利用线性四吡咯(胆红素)作为生色团来感知光的质量、数量和持续时间。光化学光传感触发构象变化，通过调节下游转录级联的靶分子来调节生命系统的行为。拟议的研究提出了这样的假设，即自真核宿主通过内生共生捕获蓝藻以来，光传感的基本机制在数十亿年的进化过程中一直保持保守。植物和蓝藻光敏色素的光转化和蛋白质-发色团相互作用的保守，植物光敏色素的进化起源，以及陆地植物的光敏色素光转化和信号活性有三个特定的目标。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应的基础和用于控制基因表达的分子结构变化。从蓝藻、绿藻、陆生植物拟南芥和普通小麦中提取的光敏色素，将被用来检验所有现存真核光敏色素的光调控构象变化触发向核转位的假说。为了验证这些假设，我们利用计算分析来指导实验设计、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的变化，并在体内评估模式陆地植物拟南芥的核转位和功能。意义重大。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)的关键调节剂。由于光敏色素在遮荫敏感中的作用，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。来自我们的见解的应用 研究可以改善营养，增进健康，延长寿命，减轻疾病和残疾的负担。此外，光敏蛋白质是研究哺乳动物蛋白质功能和定位的宝贵工具(光遗传学)，这项工作为此类系统的基础研究提供了新的工具。

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.