Genetic characterization of phytochrome nuclear bodies in plant light signaling

植物光信号传导中光敏色素核体的遗传特征

• 批准号: 8324310
• 负责人: Meng Chen
• 金额: $ 37.24万
• 依托单位: DUKE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2015-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8324310
• 关键词: Acute Promyelocytic Leukemia; Alleles; Animals; Arabidopsis; Binding; Binding Proteins; Biochemical; Biological; Biological Models; Cell Nucleus; Cells; Complement; Complex; Constitution; Coupled; Cytoplasm; Cytoplasmic Granules; Event; Genes; Genetic; Genetic Models; Genetic Screening; Genetic Transcription; Goals; In Vitro; Light; Link; Maps; Mediating; Modeling; Molecular; Morphology; Nuclear; Orthologous Gene; Pattern; Photoreceptors; Phototransduction; Physiological Processes; Phytochrome; Plants; Property; Proteasome Binding; Proteolysis; Regulation; Research; Role; Seedling; Series; Signal Transduction; Signal Transduction Pathway; Site; System; Testing; Transcriptional Regulation; Yeasts; base; body system; human disease; insight; multicatalytic endopeptidase complex; mutant; novel; phyB phytochrome; plant growth/development; protein degradation; public health relevance; receptor; research study; response; tool; yeast protein

DESCRIPTION (provided by applicant): Nuclear bodies (NBs) are distinct subnuclear domains present in both animal and plant cells. Although numerous NBs, such as Cajal bodies, PML (promyelocytic leukemia) NBs , and IGC (interchromatin granule cluster) have been extensively studied in mammalian systems, and changes in morphology and constitution of these nuclear bodies are associated with human diseases, the precise function and regulation of NBs are still poorly understood. One possible reason for this is the lack of genetic models to study NB functions. We propose to use phytochrome NBs in plant light signaling as a genetic model system to investigate general principles behind NB functions. Phytochromes are red and far-red photoreceptors regulating plant development and growth through transcription regulation. Phytochromes localize in the cytoplasm in the dark. Upon light activation, they relocate to the nucleus and form phytochrome NBs. We demonstrated that the formation of a photo-stable phytochrome B (PHYB) containing NBs is directly regulated by light and is tightly correlated to phytochrome responses. Based on these observations, we hypothesize that phytochrome NBs are directly involved in phytochrome signaling events. To test this hypothesis, we propose to: (1) identify and characterize new components required for PHYB-GFP NB formation by a confocal-based genetic screen. We have already identified twenty-nine such mutants. One locus, HMR, has been cloned, and two others rough-mapped. Strikingly, our preliminary studies show that the first gene (HMR) identified from this screen is required for both PHYB-GFP NB formation and early phytochrome signaling events including the light-dependent proteolysis of PHYA, a photo-labile phytochrome. Interestingly, HMR is structurally similar to the mammalian ortholog of a yeast protein RAD23, which is a multiubiquitin binding protein involved in protein degradation. These results provide the first genetic evidence linking phytochrome nuclear bodies with protein degradation, and demonstrate that this genetic screen will likely identify novel components linking phytochrome NB function and early phytochrome signaling events; (2) investigate the function of phytochrome NBs in early phytochrome signaling events. We propose a number of experiments to directly test whether phytochrome NBs are sites for PHYA degradation and/or transcription regulation; (3) define the function of HMR in PHYA degradation. We will test whether HMR acts as RAD23 by delivering PHYA to the proteasome for degradation. Collectively, the proposed experiments should contribute significantly to a better understanding of light signaling in plants. More importantly, they will also start to unravel general principles of NBs in cell signaling. PUBLIC HEALTH RELEVANCE: Nuclear bodies are distinct subnuclear domains present in both animal and plant systems. Changes in morphology and constitution of numerous mammalian nuclear bodies are associated with human diseases. We will take advantage of the plant phytochrome nuclear body system and use it as a genetic model to investigate the function and regulation of nuclear bodies in the context of cell signaling. Our studies should contribute significantly to our understanding of the cellular and molecular basis for human diseases.

描述（由申请人提供）：核体（NB）是动物和植物细胞中存在的不同亚核结构域。尽管卡哈尔小体、PML（早幼粒细胞白血病）NB和IGC（染色质间颗粒簇）等众多核体已在哺乳动物系统中得到广泛研究，并且这些核体的形态和构成的变化与人类疾病相关，但其精确功能对NB的监管仍然知之甚少。造成这种情况的一个可能原因是缺乏研究 NB 功能的遗传模型。我们建议在植物光信号传导中使用光敏色素 NB 作为遗传模型系统来研究 NB 功能背后的一般原理。光敏色素是红色和远红光感受器，通过转录调控来调节植物的发育和生长。在黑暗中光敏色素定位于细胞质中。光激活后，它们重新定位到细胞核并形成光敏色素 NB。我们证明，含有 NB 的光稳定光敏色素 B (PHYB) 的形成直接受光调节，并且与光敏色素反应密切相关。基于这些观察，我们假设光敏色素 NB 直接参与光敏色素信号传导事件。为了检验这一假设，我们建议：（1）通过基于共聚焦的遗传筛选来识别和表征 PHYB-GFP NB 形成所需的新成分。我们已经鉴定出二十九个这样的突变体。一个基因座 HMR 已被克隆，另外两个基因座已被粗略绘制。引人注目的是，我们的初步研究表明，从该筛选中鉴定出的第一个基因 (HMR) 是 PHYB-GFP NB 形成和早期光敏色素信号事件所必需的，包括 PHYA（一种光不稳定光敏色素）的光依赖性蛋白水解。有趣的是，HMR 在结构上与酵母蛋白 RAD23 的哺乳动物直系同源物相似，后者是一种参与蛋白质降解的多泛素结合蛋白。这些结果提供了第一个将光敏色素核体与蛋白质降解联系起来的遗传证据，并证明这种遗传筛选可能会识别出将光敏色素 NB 功能和早期光敏色素信号传导事件联系起来的新成分； (2)研究光敏色素NB在早期光敏色素信号传导事件中的功能。我们提出了许多实验来直接测试光敏色素 NB 是否是 PHYA 降解和/或转录调控的位点； (3)定义HMR在PHYA降解中的作用。我们将通过将 PHYA 递送至蛋白酶体进行降解来测试 HMR 是否充当 RAD23。总的来说，所提出的实验应该有助于更好地理解植物中的光信号。更重要的是，他们还将开始阐明 NB 在细胞信号传导中的一般原理。 公共卫生相关性：核体是动物和植物系统中存在的不同亚核域。许多哺乳动物核体的形态和构成的变化与人类疾病有关。我们将利用植物光敏色素核体系统并将其用作遗传模型来研究核体在细胞信号传导背景下的功能和调节。我们的研究应该极大地有助于我们了解人类疾病的细胞和分子基础。