Chen Ligang, Zhang Liping, Xiang Shengyuan, Chen Yanli, Zhang Haiyan, Yu Diqiu
CAS Key Laboratory of Tropical Plant Resources and Sustainable Use, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, China.
Center of Economic Botany, Core Botanical Gardens, Chinese Academy of Sciences, Menglun, Mengla, Yunnan, China.
J Exp Bot. 2021 Feb 24;72(4):1473-1489. doi: 10.1093/jxb/eraa529.
Necrotrophic fungi cause devastating diseases in both horticultural and agronomic crops, but our understanding of plant defense responses against these pathogens is still limited. In this study, we demonstrated that WRKY75 positively regulates jasmonate (JA)-mediated plant defense against necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola, and also affects the sensitivity of plants to JA-inhibited seed germination and root growth. Quantitative analysis indicated that several JA-associated genes, such as OCTADECANOID-RESPONSIVE ARABIDOPSIS (ORA59) and PLANT DEFENSIN 1.2A (PDF1.2), were significantly reduced in expression in wrky75 mutants, and enhanced in WRKY75 overexpressing transgenic plants. Immunoprecipitation assays revealed that WRKY75 directly binds to the promoter of ORA59 and represses itstranscription. In vivo and in vitro experiments suggested that WRKY75 interacts with several JASMONATE ZIM-domain proteins, repressors of the JA signaling pathway. We determined that JASMONATE-ZIM-DOMAIN PROTEIN 8 (JAZ8) represses the transcriptional function of WRKY75, thereby attenuating the expression of its regulation. Overexpression of JAZ8 repressed plant defense responses to B. cinerea. Our study provides evidence that WRKY75 functions as a critical component of the JA-mediated signaling pathway to positively regulate Arabidopsis defense responses to necrotrophic pathogens.
坏死营养型真菌会在园艺作物和农作物中引发毁灭性病害，但我们对植物针对这些病原体的防御反应的了解仍然有限。在本研究中，我们证明WRKY75正向调控茉莉酸（JA）介导的植物对坏死营养型真菌病原体灰葡萄孢和芸苔链格孢的防御反应，并且还影响植物对JA抑制种子萌发和根系生长的敏感性。定量分析表明，几个与JA相关的基因，如拟南芥十八烷酸响应基因（ORA59）和植物防御素1.2A（PDF1.2），在wrky75突变体中的表达显著降低，而在WRKY75过表达转基因植物中表达增强。免疫沉淀试验表明，WRKY75直接与ORA59的启动子结合并抑制其转录。体内和体外实验表明，WRKY75与几种茉莉酸ZIM结构域蛋白相互作用，这些蛋白是JA信号通路的抑制因子。我们确定茉莉酸ZIM结构域蛋白8（JAZ8）抑制WRKY75的转录功能，从而减弱其调控的表达。JAZ8过表达抑制了植物对灰葡萄孢的防御反应。我们的研究提供了证据，证明WRKY75作为JA介导的信号通路的关键组分，正向调控拟南芥对坏死营养型病原体的防御反应。
