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

植物激素是一种低丰度的信号分子，对植物生长发育过程中的多种过程具有重要影响。功能基因组学研究表明，经典育种选择的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转导基因。植物激素的代谢受许多环境因子的调节，在调节植物生长及其对环境变化的响应中起着重要作用。拟议的研究计划旨在了解种子如何应对环境变化的分子机制：水和后熟。 植物激素脱落酸（阿坝）调节许多发育和生理过程，包括种子休眠和萌发。干种子在高水平上积累阿坝，并且阿坝水平在种子吸胀（吸水）期间降低，这是种子萌发的关键检查点。种子吸胀过程中阿坝水平的降低受CYP707A2的调节，CYP707A2是一个编码负责阿坝催化的P450单加氧酶的基因。CYP707A2的表达受多种环境信号的调控，如硝酸盐、水分、后熟、光照和温度。Nambara实验室已经研究了CYP707A2在种子中的表达是如何被这些环境信号调节的，使用拟南芥作为模型系统。遗传和表达分析表明，CYP707A2的转录调控是环境信号传导的枢纽，并决定种子是否萌发。 种子吸胀是种子萌发的第一步。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概况，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，但限制水分吸收下的种子吸胀降低了CYP707A2的表达。后熟期是种子干燥储存的一段时间，种子的性能和发芽受到影响。我的研究小组以前证明，后熟增强CYP707A2的表达，CYP707A2缺陷突变体需要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的转录调控响应水和后熟。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。在不断变化的环境下稳定的种子萌发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的解决方案，为稳定和可持续的农业实践选择优良的作物品种。

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.