Initial Events in Photoreceptor Signaling

描述(申请人提供)：生物体改变其生长和发育以响应其周围环境变化的机制在很大程度上是未知的。植物表现出巨大的表型可塑性，因为大多数植物器官直到种子萌发后才出现，从而使器官的大小和形状可以根据当地环境进行优化。因为它们是固着的和具有光合作用的，所以植物对光环境特别敏感。光影响着从种子萌发到开花的每一个发育阶段，对幼苗的形态发生有特别显著的影响。光信号不是自主作用的，而是与温度的季节和昼夜变化以及内在发育程序相结合，以指定基因表达、细胞器发育和细胞分化的正确时空调节。这项拟议的研究旨在了解光感受器光敏色素B(PHYB)如何影响植物在生活史的不同阶段的发育。作为对光的响应，光敏色素从细胞质中分离到细胞核中的离散位置，在那里它们启动了一系列信号级联，改变了一千多个基因的表达。遗传和生化方法已经确定了一些在各种不同生长条件下与PHYB密切相关的蛋白质，但缺乏机制细节。这些研究将通过这些蛋白在信号传递、PHYB运输、酶激活或光调控基因表达中的作用来探讨PHYB信号的分子机制。主要目标是：(1)鉴定与PHYB信号早期事件有关的蛋白质，这些蛋白质将其调节的核质分配与磷酸化、信号和转录联系起来；(2)将PHYB对遮荫的检测与参与局部生长素生产的酶的激活和体型变化联系起来；(3)进行遗传筛选，以确定遮荫回避中的生长素非依赖成分。植物对光的不同反应为理解表型可塑性提供了一个独特的模型系统。因此，对植物光信号的研究不仅提供了对植物生长发育的洞察，而且还导致了调节后生动物DNA损伤、转录和脂肪代谢的保守蛋白质的发现。 项目叙事 植物对光的不同和戏剧性的反应为理解所有生物如何改变其生长和发育以应对当地环境的变化提供了一个独特的模型系统。这个系统很容易操纵，这导致了关键调控蛋白的发现，这些蛋白在植物和哺乳动物之间是保守的。因此，这项研究中提出的实验应该对分析多个生物体中复杂的信号转导网络做出重大贡献。

DESCRIPTION (provided by applicant): The mechanisms by which organisms alter their growth and development in response to changes in their ambient environment are largely unknown. Plants exhibit an enormous array of phenotypic plasticity because most plant organs do not arise until after the seed germinates, allowing organ size and shape to be optimized to the local environment. Because they are sessile and photosynthetic, plants are especially attuned to their light environment. Light influences every developmental transition from seed germination to flowering, having particularly dramatic effects on the morphogenesis of seedlings. Light signals do not act autonomously, but are integrated with seasonal and diurnal changes in temperature, as well as with intrinsic developmental programs to specify correct spatial and temporal regulation of gene expression, organelle development, and cellular differentiation. The proposed studies aim to understand how one photoreceptor, phytochrome B (PHYB), influences the development of plants at various stages of the life cycle. In response to light, phytochromes partition from the cytoplasm to discrete sites in the nucleus, where they initiate a signaling cascade that alters the expression of more than a thousand genes. Genetic and biochemical approaches have identified a number of proteins that act in close proximity to PHYB under a variety of different growth conditions, yet mechanistic details are lacking. The proposed studies will explore the molecular mechanisms of PHYB signaling by characterizing these proteins in terms of their roles in signaling, PHYB trafficking, enzyme activation, or light-regulated gene expression. The primary goals are to: (1) characterize previously identified proteins involved in early events of PHYB signaling that link its regulated nucleocytoplasmic partitioning to phosphorylation, signaling, and transcription; (2) link the detection of shade light by PHYB to the activation of enzymes involved in localized auxin production and changes in body plan; (3) perform genetic screens to define auxin-independent components in shade avoidance. The diverse responses that plants have to light provide a unique model system for understanding phenotypic plasticity. As a result, the study of light signaling in plants has not only provided insight into plant growth and development, but has also led to the discovery of conserved proteins that regulate DNA damage, transcription, and lipid metabolism in metazoans. Project Narrative The diverse and dramatic responses that plants have to light provide a unique model system for understanding how all organisms alter their growth and development in response to changes in their local environment. The system is easy to manipulate, which has resulted in the discovery of key regulatory proteins that are conserved between plants and mammals. The experiments proposed in this study should thus contribute significantly to analyses of complex signal transduction networks in multiple organisms.