Zheng Zuyu, Qamar Synan Abu, Chen Zhixiang, Mengiste Tesfaye
Department of Botany and Plant Pathology, Purdue University, 915 W. State Street, West Lafayette, IN 47907-2054, USA.
Plant J. 2006 Nov;48(4):592-605. doi: 10.1111/j.1365-313X.2006.02901.x. Epub 2006 Oct 19.
Plant WRKY transcription factors are key regulatory components of plant responses to microbial infection. In addition to regulating the expression of defense-related genes, WRKY transcription factors have also been shown to regulate cross-talk between jasmonate- and salicylate-regulated disease response pathways. The two pathways mediate resistance against different types of microbial pathogens, and there are numerous reports of antagonistic interactions between them. Here we show that mutations of the Arabidopsis WRKY33 gene encoding a WRKY transcription factor cause enhanced susceptibility to the necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola concomitant with reduced expression of the jasmonate-regulated plant defensin PDF1.2 gene. Ectopic over-expression of WRKY33, on the other hand, increases resistance to the two necrotrophic fungal pathogens. The wrky33 mutants do not show altered responses to a virulent strain of the bacterial pathogen Pseudomonas syringae, although the ectopic expression of WRKY33 results in enhanced susceptibility to this pathogen. The susceptibility of WRKY33-over-expressing plants to P. syringae is associated with reduced expression of the salicylate-regulated PR-1 gene. The WRKY33 transcript is induced in response to pathogen infection, or treatment with salicylate or the paraquat herbicide that generates activated oxygen species in exposed cells. WRKY33 is localized to the nucleus of plant cells and recognizes DNA molecules containing the TTGACC W-box sequence. Together, these results indicate that pathogen-induced WRKY33 is an important transcription factor that regulates the antagonistic relationship between defense pathways mediating responses to P. syringae and necrotrophic pathogens.
植物WRKY转录因子是植物对微生物感染作出反应的关键调控成分。除了调控防御相关基因的表达外，WRKY转录因子还被证明可调控茉莉酸和水杨酸调节的疾病反应途径之间的相互作用。这两条途径介导对不同类型微生物病原体的抗性，并且有许多关于它们之间拮抗相互作用的报道。在这里，我们表明，编码WRKY转录因子的拟南芥WRKY33基因突变会导致对坏死性真菌病原体灰葡萄孢和链格孢的易感性增强，同时茉莉酸调节的植物防御素PDF1.2基因的表达降低。另一方面，WRKY33的异位过表达增加了对这两种坏死性真菌病原体的抗性。wrky33突变体对细菌病原体丁香假单胞菌的强毒株没有表现出改变的反应，尽管WRKY33的异位表达导致对该病原体的易感性增强。WRKY33过表达植物对丁香假单胞菌的易感性与水杨酸调节的PR-1基因表达降低有关。WRKY33转录本在病原体感染、水杨酸处理或百草枯除草剂处理后被诱导，百草枯除草剂在暴露细胞中产生活性氧。WRKY33定位于植物细胞核，并识别含有TTGACC W-box序列的DNA分子。总之，这些结果表明，病原体诱导的WRKY33是一种重要的转录因子，它调节介导对丁香假单胞菌和坏死性病原体反应的防御途径之间的拮抗关系。
