Expression profiles ofBr MYB transcription factors related to glucosinolate biosynthesis and stress response in eight subspecies ofBrassica rapa

Brassica rapais a polyploid species with phenotypically diverse cultivated subspecies. Glucosinolates (GSLs) are secondary metabolites that contribute to anticarcinogenic activity and plant defense in Brassicaceae. Previously, complete coding sequences of 13BrMYBtranscription factors (TFs) related toGSLbiosynthesis were identified in theB. rapagenome. In the present study, we investigatedGSLcontent and expression levels of theseBrMYBTFs in 38 accessions belonging to eight subspecies ofB. rapa. Twelve identifiedGSLs were detected and were classified into three chemical groups based on patterns ofGSLcontent and expression profiles of theBrMYBTFs.GSLcontent andBrMYBTFexpression levels differed among genotypes, includingB. rapasubspeciespekinensis,chinensisandrapa.BrMYB28.3,BrMYB51.1andBrMYB122.2positively regulatedGSLcontent in 38 accessions. Furthermore, expression levels ofBrMYB28s andBrMYB34.3increased under most abiotic and biotic stress treatments. The threeBrMYB51paralogs also showed drastically increased expression levels after infection withPectobacterium carotovorum. The results of the present study improve our understanding of the functional diversity of these 13BrMYBTFs during the evolution of polyploidB. rapa.