大刍草耐旱优异启动子变异的挖掘与利用

The long-term cultivation of maize has led to the loss of beneficial alleles in stress response, so it has higher application value to improve the existing maize germplasm pool by the utilization of teosinte. In recent years, the studies of maize have shown that the variation of regulatory region, especially the promoter region, has a great contribution to the variation of phenotype during stress. Based on these, we have obtained four genetic groups of teosinte and elite line of maize. Then, the QTL of four genetic groups and the related candidate genes from GWAS analysis will be chose, and candidate genes with big indels in promoter between teosinte and B73 will be studied to reveal the response to drought stress at transcriptional level. The key purpose of this project is to create new drought tolerant germplasm. We plan to explore upstream regulators via the analysis of promoter (e.g.， the different transcriptional activity of promoter, different binding activity to some transcription factor) and downstream targeted genes by overexpression, comparative transcriptome and ChIP-seq. Further, we hope to uncover the related regulatory network in drought response.

长期栽培使得玉米种质中抗逆基因资源逐渐丢失，利用大刍草对现有玉米种质资源进行改良对提高其抗逆性具有较高的应用价值。同时，玉米抗逆研究表明，非编码区，尤其是启动子区域的变异对于抗逆表型变异具有较大的贡献。基于此，课题组构建了4个大刍草与玉米骨干自交系杂交的遗传群体，拟通过对该4个遗传群体的QTL定位和已有的自然群体GWAS分析，筛选大刍草和B73间启动子变异较大的候选基因进行转录水平调控耐旱响应的研究。本项目以获得抗旱新种质为最终目的，从候选基因启动子转录活性、可结合转录因子等方面挖掘上游调控基因，利用基因过表达、转录组分析、ChIP-seq等手段寻找下游靶基因并明确其生物学功能，进而揭示以候选基因为中心的耐旱调控网络。

我国非玉米原产国，玉米种质资源匮乏。种质资源遗传基础狭窄在很大程度上已经限制了玉米育种工作的进步和玉米产业的发展。加强对地方种质资源和外来种质资源的深入研究，尤其是加强对热带、亚热带种质以及玉米野生近缘种等的研究与利用是拓宽我国玉米种质资源遗传基础的重要途径。本研究利用了四种玉米野生近缘物种大刍草，将大刍草基因导入 4 种栽培玉米骨干自交系，获得了 6 个大刍草基因渗入群体，为玉米种质资源创新，为玉米驯化过程中丢失的抗性基因的挖掘与再利用提供了宝贵的遗传资源。本研究获得了一批抗旱能力显著提高的材料。发现墨西哥大刍草与栽培玉米 B73 中 ZmDRO1 基因非编码区的差异导致其本底表达水平及对 ABA 的响应差异。ZmDRO1 受 ABA 或干旱诱导越强，干旱胁迫下其根系越容易向深层土壤分布，进而促进植株抵御干旱胁迫。利用 人工合成ABA 强诱导型启动子驱动 ZmDRO1 在栽培玉米 KN5585 中表达显著提高了大田干旱胁迫下的玉米产量。ZmLBD5和ZmLBD33作为转录因子可直接参与GGPP–CPP–kaurene/acid–GA代谢过程相关基因的调控，从而影响植物激素GA和ABA的含量，进而影响植株发育和抗旱。