Comparative Transcriptomics Reveals the Transcriptional Regulation of Anthocyanin Spatial Distribution in Brassica juncea (L.) Czern

Brassica juncea exhibits diverse foliar pigmentation patterns caused by anthocyanin accumulation, but the molecular basis of margin-specific pigmentation remains unclear. Here, we combined anthocyanin measurement, comparative transcriptomics, and functional analysis of BjMYB113 to investigate anthocyanin spatial distribution in mustard. The data showed that anthocyanin content was significantly higher in the leaf margin (LM) than in the leaf interior (LI) of the bicolored accession ZD30. Transcriptome analysis identified 618 DEGs between LM and LI in ZD30, compared with only 134 DEGs in the uniformly purple accession JCS53. Enrichment analyses indicated that ZD30-specific DEGs were mainly involved in flavonoid metabolism, anthocyanin biosynthesis, and secondary metabolism. Expression profiles of genes involved in anthocyanin biosynthesis indicated that BjMYB113 and BjTT8 were more highly expressed in the pigmented margin of ZD30, together with key late biosynthetic genes (DFR, ANS, and UFGT) and GSTF. In addition, transient overexpression of BjMYB113 promoted anthocyanin accumulation in leaves, suggesting that BjMYB113 acts as a positive regulator of anthocyanin accumulation and supporting a putative model in which localized activation of anthocyanin-related genes contributes to margin-specific pigmentation in B. juncea. This study provides insight into the transcriptional regulation of anthocyanin spatial distribution in mustard.