Kizis Dimosthenis, Pagès Montserrat
Departament de genetica Molecular, Centre de Investigació i Desenvolupament, CSIC, Jordi Girona 18-26, 08034 Barcelona, Spain.
Plant J. 2002 Jun;30(6):679-89. doi: 10.1046/j.1365-313x.2002.01325.x.
The abscisic acid-responsive gene rab17 of maize is expressed during late embryogenesis, and is induced by ABA and desiccation in embryo and vegetative tissues. ABRE and DRE cis-elements are involved in regulation of the gene by ABA and drought. Using yeast one-hybrid screening, we isolated two cDNAs encoding two new DRE-binding proteins, designated DBF1 and DBF2, that are members of the AP2/EREBP transcription factor family. Analysis of mRNA accumulation profiles showed that DBF1 is induced during maize embryogenesis and after desiccation, NaCl and ABA treatments in plant seedlings, whereas the DBF2 mRNA is not induced. DNA-binding preferences of DBFs were analysed by electrophoretic mobility shift assays, and showed that both DBF1 and DBF2 bound to the wild-type DRE2 element, but not to the DRE2 mutant or to the DRE1 element which differs only in a single nucleotide. Transactivation activity using particle bombardment showed that DBF1 functioned as activator of DRE2-dependent transcription of rab17 promoter by ABA, whereas DBF2 overexpression had a repression action downregulating not only the basal promoter activity, but also the ABA effect. These results show that ABA plays a role in the regulation of DBF activity, and suggests the existence of an ABA-dependent pathway for the regulation of genes through the C-repeat/DRE element.
玉米的脱落酸应答基因rab17在胚胎发育后期表达，在胚胎和营养组织中受脱落酸和脱水诱导。ABRE和DRE顺式元件参与脱落酸和干旱对该基因的调控。利用酵母单杂交筛选，我们分离出两个编码两种新的DRE结合蛋白的cDNA，分别命名为DBF1和DBF2，它们是AP2/EREBP转录因子家族的成员。mRNA积累谱分析表明，DBF1在玉米胚胎发育期间以及植物幼苗经脱水、NaCl和脱落酸处理后被诱导，而DBF2 mRNA未被诱导。通过电泳迁移率变动分析对DBF的DNA结合偏好进行了分析，结果表明DBF1和DBF2都能与野生型DRE2元件结合，但不能与DRE2突变体或仅在单个核苷酸上不同的DRE1元件结合。利用粒子轰击进行的反式激活活性分析表明，DBF1作为脱落酸对rab17启动子DRE2依赖性转录的激活剂发挥作用，而DBF2的过表达具有抑制作用，不仅下调基础启动子活性，还下调脱落酸效应。这些结果表明脱落酸在DBF活性调控中起作用，并提示存在一条通过C-重复/DRE元件调控基因的脱落酸依赖性途径。
