Elucidating regulatory mechanisms for the expression of an Arabidopsis abscisic acid 8'-hydroxylase gene in response to environmental signals

阐明拟南芥脱落酸 8-羟化酶基因响应环境信号表达的调控机制

• 批准号: RGPIN-2019-04144
• 负责人: Nambara, Eiji
• 金额: $ 4.23万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2021
• 资助国家: 加拿大
• 起止时间: 2021-01-01 至 2022-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=737440
• 关键词: Elucidating; regulatory; mechanisms; expression; Arabidopsis

Plant hormones are low abundant signal molecules, which significantly impact a variety of processes in plant growth and development. Functional genomics research has revealed that key genetic loci selected by classical breeding for yield and stress responses encode a series of hormone metabolism and signaling genes. The metabolism of plant hormones is regulated by a number of environmental factors and play an important role in tuning plant growth and its response to changing environment. The proposed research program aims to understand the molecular mechanism of how seeds respond to environmental changes: water and after-ripening. The phytohormone abscisic acid (ABA) regulates numerous developmental and physiological processes including seed dormancy and germination. Dry seeds accumulate ABA at a high level, and the ABA levels decrease during seed imbibition (water uptake), which is a critical checkpoint for seed germination. The decrease in seed ABA levels during seed imbibition is regulated by CYP707A2, a gene encoding a P450 monooxygenase responsible for ABA catabolism. The expression of CYP707A2 is regulated by multiple environmental signals, such as nitrate, water, after-ripening, light and temperature. The Nambara lab has studied how the expression of CYP707A2 in seeds is regulated by these environmental signals using Arabidopsis as a model system. Genetic and expression analyses have suggested that transcriptional regulation of CYP707A2 is a hub of environmental signaling and determines whether seeds germinate or not. Seed imbibition is the first step in the seed germination processes. My research group has demonstrated that, during the early stage of seed imbibition, both dormant and non-dormant seeds require de novo transcription and exhibit similar transcriptiome profiles, suggesting that seed imbibition involves active mechanisms in response to water. While the expression of CYP707A2 is up-regulated during seed imbibition, seed imbibition under restricted water uptake reduces the expression of CYP707A2. After-ripening is a period of dry seed storage where seed performance and germination are affected. My research group previously demonstrated that after-ripening enhances the expression of CYP707A2, and mutants defective in CYP707A2 require a prolonged period of after-ripening for germination. However, the molecular mechanisms underlying how these environmental signals affect the expression of CYP707A2 remains largely unclear. We will focus on transcriptional regulation of CYP707A2 in response to water and after-ripening. Moreover, this program will investigate how these environmental factors (i.e. water and after-ripening) affect seed responsiveness to nitrate. Stable seed germination and subsequent seedling establishment under changing environments is a key target for plant biotechnology. Our research will help to gain a novel solution to select elite crop varieties for stable and sustainable agricultural practices.

植物激素是低丰度信号分子，对植物生长和发育的多种过程产生显着影响。功能基因组学研究表明，经典育种选择的用于产量和胁迫反应的关键遗传位点编码一系列激素代谢和信号基因。植物激素的代谢受到许多环境因素的调节，在调节植物生长及其对环境变化的反应中发挥着重要作用。拟议的研究计划旨在了解种子如何响应环境变化的分子机制：水和后熟。植物激素脱落酸 (ABA) 调节许多发育和生理过程，包括种子休眠和发芽。干燥的种子会积累较高水平的 ABA，而种子吸水（吸水）期间 ABA 水平会降低，这是种子发芽的关键检查点。种子吸胀过程中种子 ABA 水平的降低受到 CYP707A2 的调节，CYP707A2 是编码负责 ABA 分解代谢的 P450 单加氧酶的基因。 CYP707A2的表达受到多种环境信号的调节，例如硝酸盐、水、后熟、光和温度。 Nambara 实验室使用拟南芥作为模型系统，研究了这些环境信号如何调节种子中 CYP707A2 的表达。遗传和表达分析表明，CYP707A2 的转录调控是环境信号传导的中心，决定种子是否发芽。种子吸胀是种子发芽过程的第一步。我的研究小组已经证明，在种子吸胀的早期阶段，休眠和非休眠种子都需要从头转录并表现出相似的转录组特征，这表明种子吸胀涉及响应水的主动机制。虽然 CYP707A2 的表达在种子吸胀过程中上调，但限制吸水的种子吸胀会降低 CYP707A2 的表达。后熟是干燥种子储存的时期，种子性能和发芽受到影响。我的研究小组之前证明，后熟可以增强CYP707A2的表达，CYP707A2缺陷的突变体需要较长时间的后熟才能发芽。然而，这些环境信号如何影响 CYP707A2 表达的分子机制仍不清楚。我们将重点关注 CYP707A2 对水和后熟反应的转录调控。此外，该计划将研究这些环境因素（即水和后熟）如何影响种子对硝酸盐的反应性。在变化的环境下稳定的种子发芽和随后的幼苗建立是植物生物技术的关键目标。我们的研究将有助于获得一种新颖的解决方案来选择优良作物品种，以实现稳定和可持续的农业实践。