A WRKY transcription factor WRKY184 from Brassica napus L. is involved in flowering and secondary wall development in transgenic Arabidopsis thaliana

Flowering is one of the important developmental processes, and the timing of flowering can affect seed yield. Lignin is one of the main components of plant cell walls. Lack of lignin in crops will reduce its resistance to stress, which in turn threatens the production of crops. The WRKY transcription factor family is a large family in higher plants and is widely involved in various biological processes. In this study, we isolated the WRKY transcription factor WRKY184 from Brassica napus L. that can simultaneously regulate the development of stems and flowers. BnWRKY184 is a member of the IIc subfamily, localized in the nucleus and has no transcriptional activation capability. The tissue expression analysis showed that BnWRKY184 had the highest expression level in stems. Overexpression of BnWRKY184 in Arabidopsis thaliana led to early flowering and weaker stem phenotypes. The expression levels of the flowering-related genes FLOWERING LOCUS T, SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1, LEAFY and FRUITFULL were up-regulated in transgenic plants. The gene expression levels of secondary wall synthesis-related genes, such as NAC SECONDARY WALL THICKENING PROMOTING FACTOR 2, CELLULOSE SYNTHASE 7 and CELLLOSE SYNTHASE 8, were down-regulated in transgenic plants. Yeast one-hybrid and promoter-LUC showed that BnWRKY184 can directly bind to the promoter region of AtNST2 and inhibit its expression. Thus, BnWRKY184 simultaneously affected plant flowering and secondary wall development by regulating the transcriptional levels of genes involved in both processes, and BnWRKY184 can directly regulate the expression of AtFUL and AtNST2, suggesting that BnWRKY184 play roles in certain signaling pathways during plant development.