Over-expression of a WRKY transcription factor gene BoWRKY6 enhances resistance to downy mildew in transgenic broccoli plants

WRKY transcription factors play an important role in plant growth, development and immunity. In our study, a WRKY family member gene designated BoWRKY6 was isolated from broccoli (Brassica oleracea var. italica), and its expression was induced by downy mildew (Hyaloperonospora parasitica). Five transgenic broccoli lines over-expressing BoWRKY6 driven by the CaMV 35S promotor were obtained by Agrobacterium tumefaciens mediated transformation, and they demonstrated significant increased resistance to downy mildew, with resistant levels from low to very high. Real time-qualitative PCR analysis indicated that expressions of both BoWRKY6 and the pathogenesis-related gene 1 (BoPR1) in transgenic plants were obviously higher than those in WT plants after H. parasitica treatment. Lines of BWK14 and BWK31 exhibited very high resistance to downy mildew, and may serve as promising candidate materials for broccoli molecular breeding in the near future.