Qin Feng, Kakimoto Masayuki, Sakuma Yoh, Maruyama Kyonoshin, Osakabe Yuriko, Tran Lam-Son Phan, Shinozaki Kazuo, Yamaguchi-Shinozaki Kazuko
Biological Resources Division, Japan International Research Center for Agricultural Sciences (JIRCAS), 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686, Japan.
Plant J. 2007 Apr;50(1):54-69. doi: 10.1111/j.1365-313X.2007.03034.x. Epub 2007 Mar 5.
DREB1/CBFs and DREB2s are transcription factors that specifically interact with a cis-acting element, DRE/CRT, which is involved in the expression of genes responsive to cold and drought stress in Arabidopsis thaliana. The function of DREB1/CBFs has been precisely analyzed and it has been found to activate the expression of many genes responsive to cold stress containing a DRE/CRT sequence in their promoters. However, the regulation and function of DREB2-type transcription factors remained to be elucidated. In this research, we report the cloning of a DREB2 homolog from maize, ZmDREB2A, whose transcripts were accumulated by cold, dehydration, salt and heat stresses in maize seedlings. Unlike Arabidopsis DREB2A, ZmDREB2A produced two forms of transcripts, and quantitative real-time PCR analyses demonstrated that only the functional transcription form of ZmDREB2A was significantly induced by stresses. Moreover, the ZmDREB2A protein exhibited considerably high transactivation activity compared with DREB2A in Arabidopsis protoplasts, suggesting that protein modification is not necessary for ZmDREB2A to be active. Constitutive or stress-inducible expression of ZmDREB2A resulted in an improved drought stress tolerance in plants. Microarray analyses of transgenic plants overexpressing ZmDREB2A revealed that in addition to genes encoding late embryogenesis abundant (LEA) proteins, some genes related to heat shock and detoxification were also upregulated. Furthermore, overexpression of ZmDREB2A also enhanced thermotolerance in transgenic plants, implying that ZmDREB2A may play a dual functional role in mediating the expression of genes responsive to both water stress and heat stress.
DREB1/CBFs和DREB2s是转录因子，它们与顺式作用元件DRE/CRT特异性相互作用，该元件参与拟南芥中对寒冷和干旱胁迫响应的基因表达。DREB1/CBFs的功能已得到精确分析，发现它能激活许多启动子中含有DRE/CRT序列的对冷胁迫响应的基因的表达。然而，DREB2型转录因子的调控和功能仍有待阐明。在本研究中，我们报道了从玉米中克隆出一个DREB2同源基因ZmDREB2A，其转录本在玉米幼苗中受寒冷、脱水、盐和热胁迫诱导积累。与拟南芥DREB2A不同，ZmDREB2A产生两种转录本形式，定量实时PCR分析表明只有功能性转录形式的ZmDREB2A受胁迫显著诱导。此外，与拟南芥原生质体中的DREB2A相比，ZmDREB2A蛋白表现出相当高的反式激活活性，这表明ZmDREB2A激活不需要蛋白质修饰。ZmDREB2A的组成型或胁迫诱导型表达导致植物耐旱胁迫能力提高。对过表达ZmDREB2A的转基因植物进行微阵列分析发现，除了编码胚胎后期丰富（LEA）蛋白的基因外，一些与热激和解毒相关的基因也上调。此外，ZmDREB2A的过表达还增强了转基因植物的耐热性，这意味着ZmDREB2A可能在介导对水分胁迫和热胁迫响应的基因表达中发挥双重功能作用。
