A Cluster of MYB Transcription Factors Regulates Anthocyanin Biosynthesis in Carrot ( Daucus carota L.) Root and Petiole

• Published in: Frontiers in plant science 2019-01, Vol.9, p.1927-1927
• Main Authors: Iorizzo, Massimo, Cavagnaro, Pablo F, Bostan, Hamed, Zhao, Yunyang, Zhang, Jianhui, Simon, Philipp W
• Format: Article
• Language: English
• Subjects: anthocyanin accumulation; Daucus carota L; fine mapping; Plant Science; regulation; root and petiole; transcriptome
• ISSN: 1664-462X; 1664-462X
• DOI: 10.3389/fpls.2018.01927

Purple carrots can accumulate large quantities of anthocyanins in their roots and -in some genetic backgrounds- petioles, and therefore they represent an excellent dietary source of antioxidant phytonutrients. In a previous study, using linkage analysis in a carrot F mapping population segregating for root and petiole anthocyanin pigmentation, we identified a region in chromosome 3 with co-localized QTL for all anthocyanin pigments of the carrot root, whereas petiole pigmentation segregated as a single dominant gene and mapped to one of these "root pigmentation" regions conditioning anthocyanin biosynthesis. In the present study, we performed fine mapping combined with gene expression analyses (RNA-Seq and RT-qPCR) to identify candidate genes controlling anthocyanin pigmentation in the carrot root and petiole. Fine mapping was performed in four carrot populations with different genetic backgrounds and patterns of pigmentation. The regions controlling root and petiole pigmentation in chromosome 3 were delimited to 541 and 535 kb, respectively. Genome wide prediction of transcription factor families known to regulate the anthocyanin biosynthetic pathway coupled with orthologous and phylogenetic analyses enabled the identification of a cluster of six transcription factors, denominated to , associated with the regulation of anthocyanin biosynthesis. No anthocyanin biosynthetic genes were present in this region. Comparative transcriptome analysis indicated that upregulation of was always associated with anthocyanin pigmentation in both root and petiole tissues, whereas was only upregulated with pigmentation in petioles. In the petiole, the level of expression of was higher than . , a gene previously suggested as a key regulator of carrot anthocyanin biosynthesis, was not consistently associated with pigmentation in either tissue. These results strongly suggest that is a candidate gene for root anthocyanin pigmentation in all the genetic backgrounds included in this study. is a candidate gene for petiole pigmentation in all the purple carrot sources in this study. Since is co-expressed with in purple petioles, the latter gene may act also as a co-regulator of anthocyanin pigmentation in the petioles. This study provides linkage-mapping and functional evidence for the candidacy of these genes for the regulation of carrot anthocyanin biosynthesis.