Liu Q, Kasuga M, Sakuma Y, Abe H, Miura S, Yamaguchi-Shinozaki K, Shinozaki K
Biological Resources Division, Japan International Research Center for Agricultural Sciences (JIRCAS), Ministry of Agriculture, Forestry, and Fisheries, 2-1 Ohwashi, Tsukuba, Ibaraki 305-8686, Japan.
Plant Cell. 1998 Aug;10(8):1391-406. doi: 10.1105/tpc.10.8.1391.
Plant growth is greatly affected by drought and low temperature. Expression of a number of genes is induced by both drought and low temperature, although these stresses are quite different. Previous experiments have established that a cis-acting element named DRE (for dehydration-responsive element) plays an important role in both dehydration- and low-temperature-induced gene expression in Arabidopsis. Two cDNA clones that encode DRE binding proteins, DREB1A and DREB2A, were isolated by using the yeast one-hybrid screening technique. The two cDNA libraries were prepared from dehydrated and cold-treated rosette plants, respectively. The deduced amino acid sequences of DREB1A and DREB2A showed no significant sequence similarity, except in the conserved DNA binding domains found in the EREBP and APETALA2 proteins that function in ethylene-responsive expression and floral morphogenesis, respectively. Both the DREB1A and DREB2A proteins specifically bound to the DRE sequence in vitro and activated the transcription of the b-glucuronidase reporter gene driven by the DRE sequence in Arabidopsis leaf protoplasts. Expression of the DREB1A gene and its two homologs was induced by low-temperature stress, whereas expression of the DREB2A gene and its single homolog was induced by dehydration. Overexpression of the DREB1A cDNA in transgenic Arabidopsis plants not only induced strong expression of the target genes under unstressed conditions but also caused dwarfed phenotypes in the transgenic plants. These transgenic plants also revealed freezing and dehydration tolerance. In contrast, overexpression of the DREB2A cDNA induced weak expression of the target genes under unstressed conditions and caused growth retardation of the transgenic plants. These results indicate that two independent families of DREB proteins, DREB1 and DREB2, function as trans-acting factors in two separate signal transduction pathways under low-temperature and dehydration conditions, respectively.
植物生长受到干旱和低温的极大影响。尽管干旱和低温这两种胁迫差异很大，但许多基因的表达都会被它们二者所诱导。先前的实验已证实，一种名为DRE（脱水响应元件）的顺式作用元件在拟南芥脱水和低温诱导的基因表达中都起着重要作用。利用酵母单杂交筛选技术分离出了两个编码DRE结合蛋白的cDNA克隆，即DREB1A和DREB2A。这两个cDNA文库分别是从脱水处理和冷处理的莲座叶植株中制备的。DREB1A和DREB2A推导的氨基酸序列除了在分别参与乙烯响应表达和花形态建成的EREBP和APETALA2蛋白中发现的保守DNA结合结构域外，没有显著的序列相似性。DREB1A和DREB2A蛋白在体外都能特异性结合DRE序列，并在拟南芥叶原生质体中激活由DRE序列驱动的β-葡萄糖醛酸酶报告基因的转录。DREB1A基因及其两个同源基因的表达受低温胁迫诱导，而DREB2A基因及其单个同源基因的表达受脱水诱导。在转基因拟南芥植株中过表达DREB1A cDNA，不仅在非胁迫条件下诱导了靶基因的强烈表达，还导致转基因植株出现矮化表型。这些转基因植株还表现出抗冻和抗脱水能力。相比之下，过表达DREB2A cDNA在非胁迫条件下诱导靶基因的弱表达，并导致转基因植株生长迟缓。这些结果表明，两个独立的DREB蛋白家族，即DREB1和DREB2，分别在低温和脱水条件下的两个独立信号转导途径中作为反式作用因子发挥作用。
