Arabidopsis Sigma Factor Binding Proteins Are Activators of the WRKY33 Transcription Factor in Plant Defense
Arabidopsis Sigma Factor Binding Proteins Are Activators of the WRKY33 Transcription Factor in Plant Defense
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DOI：
10.1105/tpc.111.090571
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发表时间：
2011-10-01
期刊：
影响因子：
11.6
通讯作者：
Chen, Zhixiang
中科院分区：
文献类型：
--
作者：
Lai, Zhibing;Li, Ying;Chen, Zhixiang
坏死性致病菌是引起许多毁灭性植物病害的重要植物致病菌。尽管它们的影响，我们对植物对坏死性病原体的防御反应的理解是有限的。WRKY33转录因子在植物对坏死性病原体的抗性中起重要作用；因此，阐明其功能将提高我们对植物对坏死性病原体免疫的认识。在这里，我们报道了两个wrky33相互作用的蛋白，核编码的SIGMA因子结合蛋白1 （SIB1）和SIB2，它们也与质体编码的质体RNA聚合酶SIGMA FACTOR1相互作用。SIB1和SIB2都含有一个n端叶绿体靶向信号和一个假定的核定位信号，表明它们是双靶向的。双分子荧光互补表明WRKY33与植物细胞核中的SIBs相互作用。SIB1和SIB2都包含一个短的VQ基序，这对与WRKY33的相互作用很重要。这两个含有VQ基序的蛋白识别c端WRKY结构域并刺激WRKY33的DNA结合活性。与WRKY33一样，SIB1和SIB2都能被坏死性病原菌灰霉病菌（Botrytis cinerea）快速而强烈地诱导。对灰孢杆菌的抗性在sib1和sib2突变体中受损，但在sib1过表达的转基因植物中增强。这些结果表明，双靶向SIB1和SIB2作为WRKY33的激活因子在植物对坏死性病原体的防御中起作用。
Necrotrophic pathogens are important plant pathogens that cause many devastating plant diseases. Despite their impact, our understanding of the plant defense response to necrotrophic pathogens is limited. The WRKY33 transcription factor is important for plant resistance to necrotrophic pathogens; therefore, elucidation of its functions will enhance our understanding of plant immunity to necrotrophic pathogens. Here, we report the identification of two WRKY33-interacting proteins, nuclear-encoded SIGMA FACTOR BINDING PROTEIN1 (SIB1) and SIB2, which also interact with plastid-encoded plastid RNA polymerase SIGMA FACTOR1. Both SIB1 and SIB2 contain an N-terminal chloroplast targeting signal and a putative nuclear localization signal, suggesting that they are dual targeted. Bimolecular fluorescence complementation indicates that WRKY33 interacts with SIBs in the nucleus of plant cells. Both SIB1 and SIB2 contain a short VQ motif that is important for interaction with WRKY33. The two VQ motif-containing proteins recognize the C-terminal WRKY domain and stimulate the DNA binding activity of WRKY33. Like WRKY33, both SIB1 and SIB2 are rapidly and strongly induced by the necrotrophic pathogen Botrytis cinerea. Resistance to B. cinerea is compromised in the sib1 and sib2 mutants but enhanced in SIB1-overexpressing transgenic plants. These results suggest that dual-targeted SIB1 and SIB2 function as activators of WRKY33 in plant defense against necrotrophic pathogens.