Comprehensive Transcriptome–Metabolome Analysis and Evaluation of the Dark_Pur Gene from Brassica juncea that Controls the Differential Regulation of Anthocyanins in Brassica rapa

Abstract

Chinese cabbage (Brassica rapa) is a major vegetable crop in China. The accumulation of anthocyanins improves the quality and flavor of Brassica crops and is beneficial for human health. There has been great research interest in breeding purple Chinese cabbage, for which it is necessary to study the key genes and mechanisms of anthocyanin accumulation. Through distant hybridization between purple mustard (Brassica. juncea) and green Chinese cabbage (B. rapa), purple Chinese cabbage plants were obtained. Furthermore, the Dark_Pur gene was cloned in the purple Chinese cabbage plants, which came from purple mustard and may be responsible for the purple phenotype in purple Chinese cabbage plants. Through particle bombardment of isolated microspores from Chinese cabbage to transform the Dark_Pur gene, the transformed purple Chinese cabbage plant was obtained, thus verifying the function of the Dark_Pur gene. To further study the Dark_Pur gene regulatory mechanism of anthocyanin accumulation in Chinese cabbage, the purple/green Chinese cabbage lines and purple/green mustard lines were subjected to transcriptome–metabolome analysis. Three stages (cotyledon, seedling, and large-leaf stages) of the purple/green Chinese cabbage lines and purple/green mustard lines were selected for analysis. The results indicated that the expression level of the transcription factor genes BraA09g028560.3C, BraA03g019460.3C, and BraA07g035710.3C may be induced by the Dark_Pur gene and they play an important role in purple Chinese cabbage, and BjuB010898 and BjuO006089 may be responsible for anthocyanin accumulation in mustard. Studying the structural genes of the purple Chinese cabbage showed that PAL, C4H, 4CL, CHS, CHI, F3H, F3'H, FLS, DFR, ANS, and UGT were up-regulated in three growth periods. There were 22 and 10 differentially expressed metabolites (DEMs) in seedling and large-leaf stages between purple/green Chinese cabbage, respectively, and 12 and 14 differentially expressed metabolites (DEMs) in seedling and large-leaf stages between purple/green mustard, respectively, which may indicate that the Dark_Pur gene from purple mustard greatly regulates anthocyanin accumulation in purple Chinese cabbage. This study provides a foundation for further elucidating anthocyanin regulation.

A MYB Transcription Factor from Brassica juncea Regulates Purple Leaves in Pak Choi (Brassica campestris L. ssp. chinensis)

“…The BjPur gene in B. juncea was also mapped, and it encoded a new R2R3-MYB transcription factor [11], while the Dark_Pur gene and the BjPur gene were the same. The transformed purple Chinese cabbage plant was obtained via the particle bombardment of isolated microspores from Chinese cabbage to transform the Dark_Pur gene, thus verifying the function of the Dark_Pur gene [38]. In this study, the candidate interval was not further narrowed with more markers, and we hypothesized that the candidate gene regulating purple in pak choi may be the Dark_Pur gene from B. juncea.…”

“…According to their phenotypes and genotypes, the target genes were initially located in the 30,067,746-31,915,855 bp region on chromosome A03 (Figure 3). In our previous study, a new purple B. rapa variety was obtained via distant hybridization from green B. rapa × purple B. juncea, and the purple-leaf-regulating gene Dark_Pur was mapped, which encoded the transcription factor R2R3-MYB from B05 in B. juncea [31,38]. The BjPur gene in B. juncea was also mapped, and it encoded a new R2R3-MYB transcription factor [11], while the Dark_Pur gene and the BjPur gene were the same.…”

“…The results from the Dark_Pur-1 (Table S1) marker identification were consistent with the phenotype, from which we inferred that the candidate gene for the purple-leaf phenotype in pak choi was from the Dark_Pur gene on B05 in B. juncea. In our previous study, a new purple B. rapa variety was obtained via distant hybridization from green B. rapa × purple B. juncea, and the purple-leaf-regulating gene Dark_Pur was mapped, which encoded the transcription factor R2R3-MYB from B05 in B. juncea [31,38]. The BjPur gene in B. juncea was also mapped, and it encoded a new R2R3-MYB transcription factor [11], while the Dark_Pur gene and the BjPur gene were the same.…”

Efficient transformation of the isolated microspores of Chinese cabbage (Brassica rapa L. ssp. pekinensis) by particle bombardment

“…The vector pHSE401-mCherry contained the red fluorescence label promoted by mCherry and was a CRISPR/Cas9 vector. The pCAMBIA2300 vector contained the insert section of the Dark_Pur gene, with the CaMV35S promoter, eGFP, and Kan labels [ 43 ].…”

Integrated transcriptomic and metabolomic analyses reveals anthocyanin biosynthesis in leaf coloration of quinoa (Chenopodium quinoa Willd.)

“…Delphinidin is formed by flavonoid 3'-5' hydroxylase (F3'-5'H), ANS, DFR, and UFGT in the third branching pathway. Liu Y et al [13] conducted an investigation on the structural genes of purple Chinese cabbage (Brassica rapa). Their study revealed significant up-regulation of key genes including PAL, C4H, 4CL, CHS, CHI, F3H, F3'H, FLS, DFR, and ANS across all three growth stages (cotyledon, seedling, and large-leaf stages).…”