Molecular genetical analysis of plant gene expression by phytohormones.

环境胁迫，如干旱、低温和盐胁迫，触发植物激素脱落酸（ABA）的产生，进而诱导各种基因。ABA在基质关闭、种子成熟和休眠中起作用。许多abainducducible基因也在胚发生后期的种子发育过程中表达。为了从分子水平上了解植物对干旱胁迫的反应，我们克隆了水分亏缺胁迫诱导的基因，并以拟南芥为研究对象分析了这些基因的表达。利用差异杂交技术分离到9个受水分亏缺影响诱导的cdna，命名为RD（Responsive to Desic ation）。这些RD基因诱导mrna的时间不同。脱落酸诱导的mrna与指定为RD22、RD29、RD17和RD20的克隆相对应，而与指定为RD19、RD21、RD28、RD2和RD26的克隆不相对应，这表明从水分胁迫到RD基因的表达存在多种信号转导途径。RD22与蚕豆种子蛋白具有同源性。RD17与RAB蛋白序列同源。观察到缺水对RD29基因的两步诱导作用。第一次快速诱导发生在20min，第二次缓慢诱导发生在3h。ABA参与了RD29基因的第二种慢表达。在拟南芥基因组中，RD29的两个基因rd29A和rd29B串联在8kbp的区域。在转基因拟南芥和烟草中，由rd29A启动子驱动的GUS报告基因不仅在干燥胁迫下被显著诱导，而且在盐胁迫、冷胁迫或ABA处理下也被显著诱导。

Environmental stresses, such as drought, low temperature and salt stresses, trigger the production of plant hormone abscisic acid(ABA), which in turn induces various genes. ABA functions in stromatal closure, seed maturation and dormancy. Many ABAinducible genes are also expressed at the late stage of embryogenesis during seed development.In order to understand plant responses to desiccation stress at molecular level, we cloned genes that are induced by water-deficit stress and to analyze their expression using Arabidopsis thaliana. We isolated nine cDNAs induced by the effects of water deficit by using the technique of differential hybridization and named them RD(RD for Responsive to Desic ation). The timing of induction of their mRNAs varies between these RD genes. Abscisic acid induces mRNAs that correspond to clones designated RD22, RD29, RD17 and RD20 but not to those designated RD19, RD21, RD28, RD2 and RD26, indicating that there are several signal-transduction pathways from water stress to expression of RD genes. RD22 exhibits local homology to an unidentified seed protein of Vicia faba. RD17 shows sequence homology to RAB proteins. Two step induction of RD29 gene by water deficiency was observed. The first quick induction occured in 20 min and the second slow induction was observed in 3h. ABA is involved in the second slow expression of the RD29 gene. Two genes for RD29, rd29A and rd29B, are tandemly located in 8 kbp region on A. thaliana genome. The GUS reporter gene driven by the rd29A promoter was significantly induced not only by desiccation stress but also by salt and cold stresses or ABA treatment in both transgenic A. thaliana and tobacco.