脱落酸(ABA)作为植物体内的一种重要激素，在植物生长发育和植物适应环境等方面起着重要作用。与研究相对比较完善的ABA生物合成相比，调控ABA生物合成的未知因子依然较多，值得我们深入研究。本项目以ABA生物合成限速关键酶NCED3启动子融合萤火虫荧光蛋白的转基因植株构建EMS突变体库，采用冷CCD照相机筛选干旱胁迫下参与调控ABA生物合成的关键因子，以期进一步完善干旱胁迫下调控ABA生物合成的信号通路。前期工作中，我们已筛选到一个新的突变体，ced3。与野生型植株相比，ced3突变体不仅在干旱胁迫下具有较低的ABA含量和ABA生物合成基因的表达水平，而且其抗旱性也降低。通过图位克隆技术发现CED3编码一个UDP葡萄糖转移酶73C1。我们将采用遗传分析，并结合生化、细胞生物学和高通量测序的手段分析这个基因的功能。该项目的研究成果对于干旱胁迫下ABA生物合成的调控机制具有重大意义。

The phytohormone abscisic acid (ABA) regulates many aspects of plant growth and development as well as responses to the environment. In contrast with the ABA biosynthesis pathway which has been well investigated, the activation of ABA biosynthesis pathway remains largely undiscovered. To understand the signal transduction mechanism underlying the activation of ABA biosynthesis in response to drought, transgenic plants contained NCED3 promoter fused with firefly luciferase were mutated by EMS, and then we performed a forward genetic screen to isolate mutants defected in drought stress regulation of the ABA biosynthesis through cooled CCD camera. The ced3 mutant isolated in this study not only showed markedly reduced ABA content and ABA biosynthesis genes expression in response to drought compared with the wild type, but also showed hypersensitivity to drought stress. Map-based cloning results showed that CED3 encode a UDP-Glucosyl transferase 73C1. We will then functionally characterize the CED3 gene by combing genetic, biochemistry, cell biology, and transcriptome approach. Our findings will provide novel insights into the molecular mechanisms of drought-activated ABA biosynthesis in plants.