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: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=746530
• 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.

植物激素是低丰富的信号分子，这显着影响植物生长和发育中的各种过程。功能基因组学研究表明，经典育种选择的关键遗传基因座用于产量和应力反应编码一系列激素代谢和信号基因。植物激素的代谢受许多环境因素的调节，并在调整植物生长及其对不断变化的环境的反应中起着重要作用。拟议的研究计划旨在了解种子对环境变化的反应：水和成熟后的分子机制。植物激素脱甲基酸（ABA）调节许多发育和生理过程，包括种子休眠和发芽。干燥的种子在高水平上积聚ABA，在种子吸收期间的ABA水平降低（水吸收），这是种子发芽的关键检查点。种子吸收期间种子ABA水平的降低受CYP707A2的调节，CYP707A2是一种编码负责ABA分解代谢的P450单加氧酶的基因。 CYP707A2的表达受多种环境信号的调节，例如硝酸盐，水，成熟后，光和温度。 Nambara实验室已经研究了使用拟南芥作为模型系统的这些环境信号在种子中CYP707A2的表达如何调节。遗传和表达分析表明，CYP707A2的转录调控是环境信号的枢纽，并确定种子是否发芽。种子吸收是种子发芽过程中的第一步。我的研究小组表明，在种子吸收的早期阶段，休眠种子和非休眠种子都需要从头转录，并表现出相似的转录组谱，这表明种子吸收涉及响应水的主动机制。尽管在种子吸收期间，CYP707A2的表达被上调，但在受限水吸收下的种子吸收降低了CYP707A2的表达。成熟后是一个干燥的种子储存期，其中种子性能和发芽受到影响。我的研究小组先前证明，成熟后增强增强了CYP707A2的表达，而CYP707A2中有缺陷的突变体需要长时间的发芽后成熟后。然而，这些环境信号如何影响CYP707A2的表达的分子机制仍然在很大程度上不清楚。我们将重点介绍CYP707A2的转录调控，以响应水和后蒸发。此外，该计划将研究这些环境因素（即水和成熟后）如何影响种子对硝酸盐的反应。在不断变化的环境下，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，以选择精英作物品种进行稳定和可持续的农业实践。