Abstract

The transcription factor WRKY33 is a vital regulator of the biological process of the necrotrophic fungusBotrytis cinerea(B. cinerea). However, its specific regulatory mechanism remains to be further investigated. In non-heading Chinese cabbage (NHCC,Brassica campestris(syn.Brassica rapa) ssp.Chinensis), our previous study showed that BcWRKY33A is induced not only by salt stress, but also byB. cinereainfection. Here, we noticed that BcWRKY33A is expressed in trichomes and confer plant defense resistance. Disease symptoms and qRT-PCR analyses revealed thatBcWRKY33A-overexpressing and -silencing lines were less and more severely impaired, respectively, than wild type uponB. cinereatreatment. Meanwhile, the transcripts’ abundance of indolic glucosinolates’ (IGSs) biosynthetic genes is consistent with plants’B. cinereatolerance. Identification and expression pattern analysis of BcMYB51s showed that BcMYB51-3 has a similar trend to BcWRKY33A uponB. cinereainfection. Moreover, BcWRKY33A directly binds to theBcMYB51-3promoter, which was jointly confirmed by Y1H, dual-LUC, and EMSA assays. The importance of MYB51, the homolog of BcMYB51-3, in the BcWRKY33A-mediatedB. cinerearesistance was also verified using the TRV-based VIGS system. Overall, our data concludes that BcWRKY33A directly activates the expression ofBcMYB51-3and downstream IGSs’ biosynthetic genes, thereby improving theB. cinereatolerance of NHCC plants.Keywords:Botrytis cinerea;BcWRKY33A;BcMYB51-3;IGSs’ biosynthetic genes