Integrated omics and functional insights into BjMYB90-mediated regulation of BjGSTF12 for enhanced anthocyanin biosynthesis in mustard (Brassica juncea).

Abstract

Key message: Integrated transcriptome and metabolome analyses in mustard (Brassica juncea) identified BjMYB90 as a regulator of anthocyanin synthesis and BjGSTF12 as a crucial anthocyanin transport gene The amount of anthocyanin in mustard (Brassica juncea) is critical in determining their purple pigmentation. Anthocyanins are synthesized and transported to vacuoles for storage via Glutathione S-transferases (GSTs). However, the regulatory mechanisms of GSTs in Brassica plants are still unclear. Thus, integrated metabolomic and transcriptome analyses screened GST involved in mustard anthocyanin transport. The metabolome analysis identified a total of 292 metabolites in both green and purple mustard inbred lines. Among these, 21 metabolites were anthocyanins derived from cyanidin and delphinidin, which exhibited differential expressions between purple and green mustard. Through transcriptome screenings, 47 structural genes were discovered (10 PAL, 9 CHI, 6 CHS, 4 4CL, 4 C4H, 4 ANS, 4 UFGT, 2 F3H, 2 DFR, 1 FLS, and 1 F'3H). Moreover, we employed various bioinformatics methods to identify 157 potential full-length BjGST genes from Brassica databases, of which 31 genes were differentially expressed in the transcriptome. Integrated metabolomic and transcriptomic analyses indicated that the BjGSTF12 (BjuA041385) gene involves anthocyanin transport. Furthermore, functional studies showed that BjGSTF12 could restore the purple color in the stem and rosette leaves of the Arabidopsis anthocyanin transport deletion mutant tt19. Additionally, we discovered that the BjMYB90 can bind to the promoter of BjGSTF12, suggesting that the expression of the BjGSTF12 is controlled by various TFs involved in anthocyanin biosynthesis. Our findings enhance the understanding of anthocyanin biosynthesis and transport mechanisms and support B. juncea breeding through molecular biology techniques.