Interactions of WRKY15 and WRKY33 transcription factors and their roles in the resistance of oilseed rape to Sclerotinia infection

Corresponding author: Jinxing Tu (涂金星)

WRKY transcription factors are known to participate in the defence responses of higher plants. However, little is known about the roles of such proteins, especially regarding their functions in the resistance of oilseed rape (Brassica naps; 欧洲油菜) to Sclerotinia sclerotiorum (油菜菌核病), a neurotrophic fungal pathogen that causes stem rot (茎腐病). In this study, we identified BnWRKY33 as a S. sclerotiorum responsive gene that positively regulates resistance to this pathogen by enhancing the expression of genes involved in camalexin synthesis (camalexin为一种重要的植物抗毒素) and genes regulated by salicylic acid (SA) and jasmonic acid (JA). We also identified a S. sclerotiorum-responsive region in the promoter of BnWRKY33, which we revealed to be a relatively conserved W-box region in the promoters of homologous genes in different species. Using this S. sclerotiorum-responsive region as bait in a yeast one hybrid assay, we identified another WRKY transcription factor, BnWRKY15, and observed that both BnWRKY15 and BnWRKY33 could bind to this region. In addition, BnWRKY15 overexpression simultaneously increased the susceptibility of B. napus to S. sclerotiorum and down-regulated BnWRKY33 after different durations of infection. Furthermore, BnWRKY15, which contains a transcriptional repression domain, exhibited reduced transactivation (反式激活) ability and could reduce the transactivation ability of BnWRKY33 in Arabidopsis protoplast (原生质体) assays. Therefore, we suggest that the increased susceptibility of BnWRKY15-overexpressing plants results from reduced BnWRKY33 expression, which is due to the inhibition of BnWRKY33 transcriptional activation by BnWRKY15.

WRKY转录因子参与高等植物的防御响应。然而，对于这些蛋白的功能，尤其是在欧洲油菜抗一种导致茎腐病的真菌病害菌核病中的作用还了解得很少。本文鉴定了BnWRKY33基因作为欧洲油菜的响应基因，通过增强camalexin合成相关基因和水杨酸SA、茉莉酸JA调控基因的表达正向调控对于菌核病的抗性。作者同样鉴定到了BnWRKY33基因启动子区对于菌核病响应的区域，在不同物种中BnWRKY33同源基因启动子区的W-box相对保守。利用这段响应区域作为bait进行酵母单杂，作者鉴定到了另一个WRKY转录因子BnWRKY15基因，并观测到BnWRKY15和BnWRKY33均可以结合到该区域。另外，BnWRKY15基因过表达会增加欧洲油菜对于菌核病的易感性，并在侵染后不同时期下调BnWRKY33基因的表达。此外，BnWRKY15包含一个转录抑制结构域，具有减弱的反式激活能力，可以在拟南芥原生质体试验中降低BnWRKY33的反式激活能力。因此，本文表明BnWRKY15基因过表达的植株之所以对菌核病的易感是因为BnWRKY15对BnWRKY33的转录激活的抑制导致的BnWRKY33基因表达降低。

个人简介：1992-1997年，华中农业大学，硕士、博士；1997-1999年， 华中农业大学，讲师；1999-2000年，加拿大Manitoba大学，分子生物学研究、生物信息学研究；2000-2001年，DNALandMarks 公司，SNP分析；2004年，瑞典SVALOF WEIBULL AB 实验室，隐性细胞核雄性不育抑制基因的定位、转基因植物安全检测；2006年，加拿大Manitoba大学，白菜雄性不育基因克隆、BAC文库构建研究。

doi: https://doi.org/10.1111/pbi.12838