GmBZR1-1介导干旱下油菜素甾醇和生长素互作调控大豆根系发育的机制研究

The continuous climate changes increase the occurrence of drought stresses in global agricultural areas, which cause a significant reduction in soybean production. Root system architecture (RSA, shape of the roots/ the physical space /the deeper and wilder root system) can avoid drought stress by their ability to acquire more water resource. Brassinosteroids (BRs) play an important role during root development, and the cross-talk between BRs and auxin is significantly associated with the constitutive and plastic characteristics of roots. ..Transcription factor BZR1/BZR2 was well characterized as a downstream regulator of BR signaling pathway in Arabidopsis and rice. Our recent studies demonstrated that soybean GmBZR1-1 regulate the gene expression of multiple auxin synthesis, transport and response and involved in root development. However, it remains unclear how GmBZR1-1 regulate the development of soybean root and what is the role of GmBZR1-1 in the BR-auxin synergetic regulating the root system architecture under drought. ..In this study, the root phenotypes in different GmBZR1-1 genotypes soybean under moderate drought stress will be characterized. Furthermore, more auxin pathway related genes through GmBZR1-1 regulation under drought stress will be identified and confirmed . In addition, the mechanism of how GmBZR1-1 and its downstream auxin related genes regulate soybean root development using gene editing technology and soybean hairy roots system wll be carried out. The study will not only facilitate understanding the mechanism of GmBZR1-1 during soybean root development and how BR-auxin interactions under stress, but also provide a foundation for future studies on how to utilize plant hormone in developing new drought tolerance soybean cultivars.

大豆根系发育与抗旱性显著相关，植物激素油菜素甾醇和生长素对大豆根系发育起重要调控作用，但两者如何在干旱胁迫时协同调控大豆根系发育的机制仍不清楚。最近研究表明大豆油菜素甾醇信号传导转录因子GmBZR1-1可调控多个生长素合成、运输和响应的基因表达和根系发育。本课题将基于前期研究基础，综合利用遗传学、功能基因组学等手段，通过研究不同GmBZR1-1基因型大豆根系在中度干旱胁迫时根系形态建成的特征，进一步鉴定和确认干旱胁迫时GmBZR1-1调控的生长素运输、合成及响应相关的基因，构建油菜素甾醇与生长素的互作调控网络；然后利用基因编辑技术和大豆发根农杆菌诱导毛状根体系，分析GmBZR1-1及其下游生长素相关基因如何协同调控大豆根系发育。相关研究结果不但有助于明确大豆干旱胁迫下油菜素甾醇和生长素调控其根系发育的机制，也为利用植物激素调控根系发育和挖掘大豆优异抗旱基因以培育抗旱大豆新品系提供理论基础。

大豆是我国主要的粮油兼用作物，然而其根系较不发达，生长期需水量多，在豆类作物中对缺水较为敏感。根系是作物吸收水分和养分的重要器官，其形态决定了作物获得养分和水分的能力。油菜素甾醇是调控植物根系发育的关键激素，其信号转导关键因子GmBZL3在植物生长和发育中发挥作用，作为转录因子整合多个信号途径协调转录网络的调控。本项目首先鉴定了大豆油菜素甾醇信号传导关键转录因子GmBZL3的保守的关键调控氨基酸位点，利用拟南芥油菜素甾醇不敏感突变体bri1-5构建转基因分析GmBZL3对根系发育的功能，并且GmBZL3过量表达可互补bri1-5对所施加的外源BR的敏感性，进一步表明GmBZL3在油菜素甾醇信号传导反应途径中发挥较为保守的功能。利用ChIP-Seq实验鉴定了GmBZL3调控基因，表明其参与大豆根系生长发育的多个进程，并揭示了BR信号通路与发育过程的下游组分之间的交叉。通过对GmBZL3调控的生长素运输、合成及响应相关的基因的调控网络进行了挖掘，并利用酵母单杂交实验验证了GmBZL3调控两个生长素合成和响应相关基因的启动子。我们同时构建了多组表达谱数据集，包括不同浓度BR合成抑制剂对苗期大豆基因表达水平的调控，以及不同程度干旱（轻度，重度，重度及重度干旱后恢复）对苗期大豆基因表达水平的调控。利用以上表达谱数据与ChIP-Seq实验鉴定GmBZL3的调控基因联合分析，发现不同BR水平下大豆GmBZL3靶基因的表达受到严格调控。最后利用大豆发根农杆菌诱导毛状根体系分析了GmBZL3如何协同调控干旱下大豆根系发育。过量表达GmBZL3转基因复合体毛根数目较对照少，但是其转GmBZL3和GmBZL3P219L大豆毛状根复合体丙二醛和脯氨酸显著高于非转基因，表明过表达GmBZL3参与提高了大豆的抗旱性。项目研究结果为油菜素甾醇和生长素激素互作调控大豆根系发育及干旱下育种提供了基因储备和理论指导。