Light Responsive Genes

描述（申请人提供）：光是调节植物发育和代谢过程的重要信号。在拟南芥中已经表征了用于感知不同波长的光的光感受器。其中，光敏色素A（phyA），这是由远红光激活，已成为感光体，在幼苗去黄化中起着重要作用。我们的长期目标是识别和表征参与phyA信号转导的信号中间体和机制，以实现下游发育反应。为此，我们已经鉴定了phyA信号传导缺陷的突变体pat和laf。我们将专注于识别PAT和LAF蛋白的生化作用机制，以及它们如何与phyA信号网络中的其他中间体起作用。特别是，我们对phyA信号如何修饰这些蛋白质并调节其丰度感兴趣。一个主要的焦点是研究myb型转录激活因子LAF 1及其下游靶点和相互作用蛋白的调控。我们已经表明，COP 1，光形态发生的阻遏物，是一种E3连接酶，可以泛素化LAF 1在体外。将在体外和转基因植物中研究LAF 1通过COP 1介导的phyA信号转导中的泛素化的调节。SUMO（small ubiquitin-like modifier，小泛素样修饰物）对蛋白质的结合是一种重要的信号调节机制。我们有间接证据表明LAF 1可以被SUMO化，因为它与COP 1共定位在核斑点中，这是一种与SUMO结合相关的亚核定位模式。我们将研究类小泛素化在LAF 1调控和phyA反应传递中的作用。我们将分析的另一个突变体是pat 1，它属于植物特异性GRAS信号调节因子家族。PAT 1和它的同源物SCL 21在phyA信号传导中可能的冗余功能关系将被检查。第三个基因PAT 3和一个密切的同系物PAT 3 h似乎只参与一个子集的phyA信号转导反应。我们将详细描述这些基因在phyA信号转导中的作用。上述蛋白的表征将揭示以前未知的phyA信号转导机制。

DESCRIPTION (provided by applicant): Light is an important signal for regulation of plant development and metabolic processes. The photoreceptors for perception of different wavelengths of light have been characterized in Arabidopsis. Amongst these, phytochrome A (phyA), which is activated by far-red light, has emerged as the photoreceptor that plays a major role in seedling de-etiolation. Our long-term objective is to identify and characterize the signaling intermediates and mechanisms involved in transduction of the phyA signal to enable downstream developmental responses. To this end, we have identified mutants pat and lafdefective in phyA signaling. We will focus on identification of the biochemical mechanisms of action of PAT and LAF proteins and how they act with other intermediates in the phyA signaling network. In particular, we are interested in how phyA signals modify these proteins and regulate their abundance. A major focus is to study the regulation of the myb-type transcription activator, LAF1, its downstream targets and interacting proteins. We have shown that COP1, a repressor of photomorphogenesis, is an E3 ligase and can ubiquitinate LAF1 in vitro. The regulation of LAF1 by COP1-mediated ubiquitination in phyA signaling will be investigated in vitro and in transgenic plants. Conjugation of proteins by SUMO (small ubiquitin-like modifier) is emerging as an important regulatory mechanism of signaling. We have indirect evidence that LAF1 could be sumoylated as it is co-localized with COP1 in nuclear speckles, a subnuclear localization pattern associated with SUMO conjugation. We will investigate the role of sumoylation in LAF1 regulation and transmission of phyA responses. The other mutant we will analyze is pat1, which belongs to the plant-specific GRAS family of signal regulators. The possible redundant functional relationship between PAT1 and its close homolog SCL21 in phyA signaling will be examined. A third gene PAT3 and a close homolog PAT3h seem to participate only in a subset of phyA signaling responses. We will characterize the role of these genes in detail in the phyA signal transduction. Characterization of the above proteins will uncover previously unknown mechanisms of phyA signal transduction.