Tao Zeng, Liu Hongbo, Qiu Deyun, Zhou Yan, Li Xianghua, Xu Caiguo, Wang Shiping
National Key Laboratory of Crop Genetic Improvement, National Center of Plant Gene Research (Wuhan), Huazhong Agricultural University, Wuhan 430070, China.
Plant Physiol. 2009 Oct;151(2):936-48. doi: 10.1104/pp.109.145623. Epub 2009 Aug 21.
Although allelic diversity of genes has been reported to play important roles in different physiological processes, information on allelic diversity of defense-responsive genes in host-pathogen interactions is limited. Here, we report that a pair of allelic genes, OsWRKY45-1 and OsWRKY45-2, which encode proteins with a 10-amino acid difference, play opposite roles in rice (Oryza sativa) resistance against bacterial pathogens. Bacterial blight caused by Xanthomonas oryzae pv oryzae (Xoo), bacterial streak caused by Xanthomonas oryzae pv oryzicola (Xoc), and fungal blast caused by Magnaporthe grisea are devastating diseases of rice worldwide. OsWRKY45-1-overexpressing plants showed increased susceptibility and OsWRKY45-1-knockout plants showed enhanced resistance to Xoo and Xoc. In contrast, OsWRKY45-2-overexpressing plants showed enhanced resistance and OsWRKY45-2-suppressing plants showed increased susceptibility to Xoo and Xoc. Interestingly, both OsWRKY45-1- and OsWRKY45-2-overexpressing plants showed enhanced resistance to M. grisea. OsWRKY45-1-regulated Xoo resistance was accompanied by increased accumulation of salicylic acid and jasmonic acid and induced expression of a subset of defense-responsive genes, while OsWRKY45-2-regulated Xoo resistance was accompanied by increased accumulation of jasmonic acid but not salicylic acid and induced expression of another subset of defense-responsive genes. These results suggest that both OsWRKY45-1 and OsWRKY45-2 are positive regulators in rice resistance against M. grisea, but the former is a negative regulator and the latter is a positive regulator in rice resistance against Xoo and Xoc. The opposite roles of the two allelic genes in rice-Xoo interaction appear to be due to their mediation of different defense signaling pathways.
尽管已有报道称基因的等位基因多样性在不同生理过程中发挥重要作用，但关于宿主-病原体相互作用中防御反应基因的等位基因多样性的信息却很有限。在此，我们报道了一对等位基因OsWRKY45-1和OsWRKY45-2，它们编码的蛋白质有10个氨基酸的差异，在水稻（Oryza sativa）对细菌病原体的抗性中发挥相反作用。由水稻黄单胞菌稻致病变种（Xoo）引起的白叶枯病、由水稻黄单胞菌稻生致病变种（Xoc）引起的细菌性条斑病以及由稻瘟病菌引起的稻瘟病是全球范围内水稻的毁灭性病害。过表达OsWRKY45-1的植株对白叶枯病菌的敏感性增加，而敲除OsWRKY45-1的植株对Xoo和Xoc的抗性增强。相反，过表达OsWRKY45-2的植株抗性增强，而抑制OsWRKY45-2表达的植株对Xoo和Xoc的敏感性增加。有趣的是，过表达OsWRKY45-1和OsWRKY45-2的植株对稻瘟病菌的抗性均增强。OsWRKY45-1调控的对白叶枯病菌的抗性伴随着水杨酸和茉莉酸积累的增加以及一部分防御反应基因的诱导表达，而OsWRKY45-2调控的对白叶枯病菌的抗性伴随着茉莉酸积累的增加但水杨酸积累未增加以及另一部分防御反应基因的诱导表达。这些结果表明，OsWRKY45-1和OsWRKY45-2在水稻对稻瘟病菌的抗性中均为正调控因子，但前者在水稻对Xoo和Xoc的抗性中是负调控因子，后者是正调控因子。这两个等位基因在水稻与Xoo相互作用中的相反作用似乎是由于它们介导了不同的防御信号通路。
