DcMYB113, a root‐specific R2R3‐MYB, conditions anthocyanin biosynthesis and modification in carrot

Abstract

Summary Purple carrots, the original domesticated carrots, accumulate highly glycosylated and acylated anthocyanins in root and/or petiole. Previously, a quantitative trait locus (QTL) for root‐specific anthocyanin pigmentation was genetically mapped to chromosome 3 of carrot. In this study, an R2R3‐MYB gene, namely DcMYB113, was identified within this QTL region. DcMYB113 expressed in the root of ‘Purple haze’, a carrot cultivar with purple root and nonpurple petiole, but not in the roots of two carrot cultivars with a purple root and petiole (Deep purple and Cosmic purple) and orange carrot ‘Kurodagosun’, which appeared to be caused by variation in the promoter region. The function of DcMYB113 from ‘Purple haze’ was verified by transformation in ‘Cosmic purple’ and ‘Kurodagosun’, resulting in anthocyanin biosynthesis. Transgenic ‘Kurodagosun’ carrying DcMYB113 driven by the CaMV 35S promoter had a purple root and petiole, while transgenic ‘Kurodagosun’ expressing DcMYB113 driven by its own promoter had a purple root and nonpurple petiole, suggesting that root‐specific expression of DcMYB113 was determined by its promoter. DcMYB113 could activate the expression of DcbHLH3 and structural genes related to anthocyanin biosynthesis. DcUCGXT1 and DcSAT1, which were confirmed to be responsible for anthocyanins glycosylation and acylation, respectively, were also activated by DcMYB113. The WGCNA identified several genes co‐expressed with anthocyanin biosynthesis and the results indicated that DcMYB113 may regulate anthocyanin transport. Our findings provide insight into the molecular mechanism underlying root‐specific anthocyanin biosynthesis and further modification in carrot and even other root crops.

The novel gene BrMYB2, located on chromosome A07, with a short intron 1 controls the purple-head trait of Chinese cabbage (Brassica rapa L.)

“…Recent studies of purple head Chinese cabbage revealed that total anthocyanin content is associated with high expression of only BrMYB2 (Bra004162) among these three BrMYBs, accompanied by upregulation of BrTT8 and a series of ABGs, including BrF3'H, BrDFR, BrANS, BrUGTs, and BrGSTs 10,27 . Recent advances have shown that MYBs activate bHLHs and ABGs through strong interactions with bHLHs to promote anthocyanin biosynthesis in crop plants [38][39][40] . In purple cauliflower and red cabbage, BoMYB2 is responsible for the purple trait by interacting with BoHLHs and related ABGs [15][16][17] , and homologous comparisons showed that BrMYB2 is highly homologous with BoMYB2 (Fig.…”

Insights into long non-coding RNA regulation of anthocyanin carrot root pigmentation

“…Most of the known genes of the pathway and their main regulators were differentially expressed between the two genotypes (Supplementary Table S4). Several genes were induced in purple tissues and they mainly comprised genes representing: i) the early step in the flavonoid/anthocyanin pathway, like chalcone synthase ( DcCHS1 /DCAR_030786); chalcone isomerase ( DcCHI1 /DCAR_027694) and ( DcCHIL /DCAR_019805); flavanone 3-hydroxylase ( DcF3H1 /DCAR_009483), and flavonoid 3′-hydroxylase ( DcF3’H1 /DCAR_014032); ii) cytochrome P450 (CYP450) proteins, putatively related to the flavonoid and isoflavonoid biosynthesis pathways 23,44 ; iii) ATP-binding cassette (ABC) transporters, potentially related to anthocyanin transport 45,46 ; and iv) genes from the late steps of the pathway, like dihydro-flavonol 4-reductase ( DcDFR1 /DCAR_021485), leucoanthocyanidin dioxygenase ( DcLDOX1 / DCAR_006772), and UDP-glycosyltransferase ( DcUFGT /DCAR_009823) and the recently described DcUCGXT1 /DCAR_021269 and DcSAT1 /MSTRG.8365, which were confirmed to be responsible for anthocyanins glycosylation and acylation, respectively 26,47 . Finally, most significant regulatory genes of the pathway, belonging to the MYB, bHLH and WD40 TF gene families 21,23–26 were also differentially expressed between purple and orange genotypes (Supplementary Table S4).…”

“…DcbHLH3 , DcUCGXT1 and DcSAT1 ) also displayed no tissue specificity. DcbHLH3 was described as a co-regulator in anthocyanin biosynthesis, while DcUCGXT1 and DcSAT1 participate in anthocyanin glycosylation and acylation, respectively 26,47 . Additionally, seven TFs showed xylem preferential expression-specificity, while only one was preferentially expressed specifically in phloem.…”

“…In the same direction, several recent works 16,23–25,47 focused on the role of carrot TFs putatively involved in the regulation of anthocyanin biosynthesis in purple genotypes, particularly those belonging to the ‘MBW’ complex (i.e., R2R3– M YB, basic helix-loop-helix - b HLH- and W D-repeat TFs). Two recent reports showed that three R2R3–MYB TFs are involved in the P 1 and P 3 loci: DcMYB113 has been suggested to correspond to P 1 47 , while DcMYB6 and DcMYB7 were proposed as the two main candidate TFs underlying the carrot root anthocyanin pigmentation in the P 3 locus 25 . However, knockdown and overexpression functional analyses demonstrated that DcMYB7 (but not DcMYB6 ) is the P 3 gene controlling purple pigmentation in carrot roots 26 .…”

A functional chromogen geneCfrom wild rice is involved in a different anthocyanin biosynthesis pathway inindicaandjaponica

“…The R2R3-MYB TFs were often identified as determinants of variation in anthocyanin pigmentation and have been identified in many higher plant species [12][13][14][15][16][17]. In a previous study, OsC1, OsRb and OsDFR were identified as the determinants of anthocyanin biosynthesis in rice leaves [18].…”