Regulation of seedling de-etiolation by light

项目概述：拟南芥光敏色素（phychrome, phy）家族由5个成员（phyA至phyE）组成，它们控制着对环境光环境的许多发育反应。在光感觉和生化功能表征以及信号中间体的识别和功能表征方面取得了重大进展。然而，物理信号的生化机制尚不清楚。为了检查早期物理信号事件，物理相互作用因子如PIF1已被分离和表征。PIF1是一种基本的螺旋-环-螺旋（bHLH）转录因子，与phyA和phyB的生物活性形式以及另一种bHLH因子PIF3强烈相互作用。PIF1结合在许多光调节启动子中常见的G-box (CACGTG) DNA序列基序。PIF1在瞬时实验中也被证明可以激活转录，并且转录激活活性在远红光和红光下分别以依赖phyA和phyb的方式下调。PIF1过表达者和PIF1 T-DNA插入突变体表现出缺陷的幼苗去黄化，包括异常的下胚轴伸长和发育调节的变绿损失。这些结果表明，PIF1是物理介导控制幼苗去黄化过程的关键调节因子。本研究将采用分子遗传学、生物化学和功能基因组学等方法研究PIF1控制幼苗去黄化的分子机制。具体来说，PIF1靶基因将被鉴定和功能表征，PIF1的分子功能将被研究，以检查它是否作为一个天然靶基因启动子的转录激活因子或抑制因子。此外，将在体内研究PIF1-phy和PIF1-PIF3之间物理相互作用的生物学意义。由于PIF1是主要的物理信号伙伴，其活动受物理调节，本研究结果将为物理信号传导机制提供基础信息。预期更广泛的影响：光可以说是控制植物生长发育的最重要的环境因素之一，包括许多农学上重要的性状，如种子发芽、幼苗建立和存活、植物高度、叶面积、开花时间和人工林密度。了解光调控植物生长发育的机制将为农业生物技术的应用提供良好的工具，以减少肥料用量，提高作物产量。这一建议也非常适合培养下一代科学家，包括本科生、研究生和博士后。他们在光信号方面的训练将给他们一个独特的机会，为光生物学和生物技术领域做出重大贡献。

PROJECT SUMMARYIntellectual Merits: The phytochrome (phy) family of sensory photoreceptors in Arabidopsis consists of five members (phyA to phyE) that control many developmental responses to the ambient light environment. Significant progress has been made on characterization of photosensory and biochemical functions and in the identification and functional characterization of signaling intermediates. However, the biochemical mechanism of phy signaling is still not clear. To examine early phy signaling events, phy interacting factors such as PIF1 have been isolated and characterized. PIF1 is a basic helix-loop-helix (bHLH) transcription factor that interacts strongly with the biologically active form of phyA and phyB, as well as another bHLH factor, PIF3. PIF1 binds to a G-box (CACGTG) DNA sequence motif commonly found in many light regulated promoters. PIF1 has also been shown to activate transcription in a transient assay, and the transcriptional activation activity was downregulated by far-red and red light in a phyA- and phyB-dependent manner, respectively. PIF1 overexpressors and pif1 T-DNA insertional mutants showed defective seedling de-etiolation, including aberrant hypocotyl elongation and developmentally regulated loss of greening. These results suggest that PIF1 is a key regulator of the phy-mediated control of the seedling de-etiolation process. The proposed study will investigate the molecular mechanism by which PIF1 controls seedling de-etiolation using molecular genetic, biochemical and functional genomic approaches. Specifically, the PIF1 target genes will be identified and functionally characterized, and the molecular function of PIF1 will be investigated to examine whether it acts as a transcriptional activator or repressor from a native target gene promoter. In addition, the biological significance of physical interactions between PIF1-phy and PIF1-PIF3 will be investigated in vivo. Since PIF1 is a primary phy-signaling partner whose activity is regulated by phy, the results from this study will provide fundamental information on the mechanism of phy signaling.Expected Broader Impacts: Light is arguably one of the most important environmental factors controlling plant growth and development, including many agronomically important traits such as seed germination, seedling establishment and survival, plant height, leaf area, flowering time and plantation density. Understanding the mechanism of light-regulated plant growth and development will provide excellent tools to apply in agricultural biotechnology for increased crop production using reduced amount of fertilizers. This proposal is also ideally suited for training of the next generation of scientists, including undergraduate, graduate and postdoctoral students. Their training in light signaling will give them a unique opportunity to make significant contributions to the field of photobiology and biotechnology.