拟南芥MADS-box基因AGL21参与生长素和ABA信号调控根系构型的分子机制研究

Root is one of the most important organs for plant survival. Plant root system architecture is dramatically plastic, which is influenced by various environmental and internal cues. MADS-box transcription factors are well known key regulators of flower development but their roles in root development remain poorly understood. In our previous study, we characterized the MADS-box transcription factor AGL21, which plays a crucial role in lateral root development through regulating auxin biosynthesis in the root. Its expression is induced by many plant hormones and environmental stresses, such as ABA, IAA, and nitrogen deficiency. AGL21 also played a role in the ABA- and nitrogen-regulated root development as well as in the cross-talk between ABA and IAA signalling. In this project, we plan to investigate the mechanisms by which AGL21 regulates auxin biosynthesis in the root and participates in the cross-talk between ABA and IAA signalling to modulate root development. Meanwhile, we will study whether AGL21 is involved in the regulatory process of NO3--modulated root development. Taken together, this project will help us understand the molecular mechanism by which environmental cues and internal hormone signals cooperatively regulate root system architecture through AGL21, which will provide useful guidelines and candidate genes for improving root system of crops.

根系是植物最重要的器官之一，其构型是高度可塑的，受到多种环境和內源信号的调控。MADS-box转录因子是一类熟知的在开花调控和花型发育中起重要作用的调控因子，但是它们在根系发育中的作用知之甚少。我们的前期工作发现了一个MADS-box转录因子AGL21通过影响根系中生长素的合成来调控侧根的发育。该基因的表达受到激素ABA、IAA和环境胁迫信号的诱导，参与ABA和低氮对根系发育的调控，同时可能参与ABA与IAA信号通路之间的交互作用。本项目拟进一步研究AGL21如何调控根系中生长素的合成，如何参与ABA和IAA的cross-talk来调控根系构型的分子机制。同时，我们还将探讨AGL21是否参与ABA介导的硝酸根对根系发育的调控过程。本项目的实施将将有助于我们认知外源环境信号和內源的激素信号如何通过AGL21相互协作对根系构型进行调控的分子机理，为改良作物的根系构型提供理论基础和候选基因。

根系是植物最重要的器官之一，其构型是高度可塑的，受到多种环境和內源信号的调控。MADS-box转录因子是一类熟知的在开花调控和花型发育中起重要作用的调控因子，但是它们在根系发育中的作用知之甚少。我们的之前的工作发现了一个MADS-box转录因子AGL21通过影响根系中生长素的合成来调控侧根的发育。该基因的表达受到激素ABA、IAA和多种环境胁迫信号的诱导，参与ABA和低氮对根系发育的调控，同时可能参与ABA与IAA信号通路之间的交互作用。本项目旨在进一步研究AGL21如何调控ABA和生长素信号的cross-talk调控根系发育。我们的研究结果发现AGL21参与ABA对根系构型的调控， AGL21过表达株系的侧根发生相较于野生型对ABA的抑制更加明显，其突变体则更不敏感。同时我们发现在萌发阶段AGL21过表达对ABA的抑制超敏感，agl21突变体对ABA的抑制不敏感。通过对ABA信号通路基因表达量的分析，我们发现AGL21位于ABA信号通路TYPE 2C PROTEIN PHOSPHATASES (PP2Cs)和SnRKs的下游，ABI3，ABI4，ABI5的上游，并且AGL21正调控ABI5的表达和蛋白水平，其在种子中的表达模式与ABI5十分类似。 进一步通过ChIP-qPCR分析发现ABI5是AGL21的直接靶基因，AGL21可以直接结合在ABI5的启动子区调控ABI5的表达。已有报道表明ABI5可以通过调控PIN1来调控根系中生长素的分布，从而调控根系的构型，因而，ABI5可能是AGL21参与ABA和生长素cross-talk调控根系构型的重要节点基因。