Wang Zheng, Fang Hedi, Chen Yu, Chen Keping, Li Guanying, Gu Shoulai, Tan Xiaoli
Institute of Life Sciences, Jiangsu University, 301, Xuefu Road, Zhenjiang, 212013, China.
Mol Plant Pathol. 2014 Sep;15(7):677-89. doi: 10.1111/mpp.12123. Epub 2014 Apr 10.
Sclerotinia sclerotiorum causes a devastating disease in oilseed rape (Brassica napus) resulting in a tremendous yield loss worldwide. Studies on various host-pathogen interactions have shown that plant WRKY transcription factors are essential for defence. For the B. napus-S. sclerotiorum interaction, little direct evidence has been found with regard to the biological roles of specific WRKY genes in host resistance. In this study, we isolated a B. napus WRKY gene, BnWRKY33, and found that the gene is highly responsive to S. sclerotiorum infection. Transgenic B. napus plants overexpressing BnWRKY33 showed markedly enhanced resistance to S. sclerotiorum, constitutive activation of the expression of BnPR1 and BnPDF1.2, and inhibition of H2 O2 accumulation in response to pathogen infection. Further, we isolated a mitogen-activated protein (MAP) kinase substrate gene, BnMKS1, and found that not only can BnWRKY33 interact with BnMKS1, which can also interact with BnMPK4, using the yeast two-hybrid assay, consistent with their collective nuclear localization, but also BnWRKY33, BnMKS1 and BnMPK4 are substantially and synergistically expressed in response to S. sclerotiorum infection. In contrast, the three genes showed differential expression in response to phytohormone treatments. Together, these results suggest that BnWRKY33 plays an important role in B. napus defence to S. sclerotiorum, which is most probably associated with the activation of the salicylic acid (SA)- and jasmonic acid (JA)-mediated defence response and inhibition of H2 O2 accumulation, and we propose a potential mechanism in which BnMPK4-BnMKS1-BnWRKY33 exist in a nuclear localized complex to regulate resistance to S. sclerotiorum in oilseed rape.
核盘菌会引发油菜（甘蓝型油菜）的毁灭性病害，在全球范围内导致产量大幅损失。对多种宿主 - 病原体相互作用的研究表明，植物WRKY转录因子对防御至关重要。对于甘蓝型油菜 - 核盘菌的相互作用，关于特定WRKY基因在宿主抗性中的生物学作用，几乎没有直接证据。在本研究中，我们分离出一个甘蓝型油菜WRKY基因BnWRKY33，发现该基因对核盘菌感染高度响应。过表达BnWRKY33的转基因甘蓝型油菜植株对核盘菌的抗性显著增强，BnPR1和BnPDF1.2的表达组成性激活，并且在病原体感染时H2O2积累受到抑制。此外，我们分离出一个丝裂原活化蛋白（MAP）激酶底物基因BnMKS1，发现通过酵母双杂交试验，BnWRKY33不仅能与BnMKS1相互作用，BnMKS1还能与BnMPK4相互作用，这与它们共同的核定位一致，而且BnWRKY33、BnMKS1和BnMPK4在响应核盘菌感染时大量协同表达。相反，这三个基因在植物激素处理时表现出差异表达。总之，这些结果表明BnWRKY33在甘蓝型油菜对核盘菌的防御中起重要作用，这很可能与水杨酸（SA）和茉莉酸（JA）介导的防御反应的激活以及H2O2积累的抑制有关，并且我们提出了一种潜在机制，即BnMPK4 - BnMKS1 - BnWRKY33存在于一个核定位复合物中，以调节油菜对核盘菌的抗性。
