Zhang Juan, Peng Youliang, Guo Zejian
State Key Laboratory of Agrobiotechnology, Department of Plant Pathology, China Agricultural University, Yuanmingyuan West Road 2, Beijing 100094, China.
Cell Res. 2008 Apr;18(4):508-21. doi: 10.1038/cr.2007.104.
WRKY transcription factors have many regulatory roles in response to biotic and abiotic stresses. In this study, we isolated a rice WRKY gene (OsWRKY31) that is induced by the rice blast fungus Magnaporthe grisea and auxin. This gene encodes a polypeptide of 211 amino-acid residues and belongs to a subgroup of the rice WRKY gene family that probably originated after the divergence of monocot and dicot plants. OsWRKY31 was found to be localized to the nucleus of onion epidermis cells to transiently express OsWRKY31-eGFP fusion protein. Analysis of OsWRKY31 and its mutants fused with a Gal4 DNA-binding domain indicated that OsWRKY31 has transactivation activity in yeast. Overexpression of the OsWRKY31 gene was found to enhance resistance against infection with M. grisea, and the transgenic lines exhibited reduced lateral root formation and elongation compared with wild-type and RNAi plants. The lines with overexpression showed constitutive expression of many defense-related genes, such as PBZ1 and OsSci2, as well as early auxin-response genes, such as OsIAA4 and OsCrl1 genes. Furthermore, the plants with overexpression were less sensitive to exogenously supplied IBA, NAA and 2,4-D at high concentrations, suggesting that overexpression of the OsWRKY31 gene might alter the auxin response or transport. These results also suggest that OsWRKY31 might be a common component in the signal transduction pathways of the auxin response and the defense response in rice.
WRKY转录因子在应对生物和非生物胁迫方面具有多种调控作用。在本研究中，我们分离出一个水稻WRKY基因（OsWRKY31），该基因受稻瘟病菌Magnaporthe grisea和生长素诱导。该基因编码一个由211个氨基酸残基组成的多肽，属于水稻WRKY基因家族的一个亚组，该亚组可能在单子叶植物和双子叶植物分化后起源。通过在洋葱表皮细胞中瞬时表达OsWRKY31-eGFP融合蛋白，发现OsWRKY31定位于细胞核。对与Gal4 DNA结合结构域融合的OsWRKY31及其突变体的分析表明，OsWRKY31在酵母中具有反式激活活性。发现过表达OsWRKY31基因可增强对稻瘟病菌感染的抗性，与野生型和RNA干扰植株相比，转基因株系的侧根形成和伸长减少。过表达株系表现出许多防御相关基因的组成型表达，如PBZ1和OsSci2，以及早期生长素响应基因，如OsIAA4和OsCrl1基因。此外，过表达植株对高浓度外源供应的吲哚丁酸、萘乙酸和2,4-二氯苯氧乙酸的敏感性较低，这表明过表达OsWRKY31基因可能改变生长素响应或运输。这些结果还表明，OsWRKY31可能是水稻生长素响应和防御响应信号转导途径中的一个共同组分。
