Initial Events in Photoreceptor Signaling

描述（由申请人提供）：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发芽后才出现，允许器官的大小和形状根据当地环境进行优化。因为它们是无根的和光合作用的，植物特别适应它们的光环境。光影响从种子萌发到开花的每一个发育过程，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，而是与季节和昼夜温度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。本研究旨在了解光感受器光敏色素B （phytochrome B， PHYB）在植物生命周期的不同阶段如何影响植物的发育。光敏色素对光的反应是从细胞质分裂到细胞核的离散位点，在那里它们启动了一个信号级联，改变了一千多个基因的表达。遗传和生化方法已经确定了许多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。拟建的研究将通过表征这些蛋白质在信号传导、PHYB运输、酶激活或光调节基因表达中的作用来探索PHYB信号传导的分子机制。主要目标是：(1)表征先前鉴定的涉及PHYB信号传导早期事件的蛋白质，这些事件将其调节的核质分配与磷酸化，信号传导和转录联系起来；(2)将PHYB对遮荫光的检测与参与生长素局部生成和机体计划变化的酶的激活联系起来；(3)进行遗传筛选，确定生长素不依赖于遮荫的成分。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深入了解，而且还发现了在后生动物中调节DNA损伤、转录和脂质代谢的保守蛋白。

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.