Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2013
Publication Date: March 24, 2013
Repository URL: http://handle.nal.usda.gov/10113/56790
Citation: Yildiz, M., Willis, D.K., Cavagnaro, P.F., Iorizzo, M., Abak, K., Simon, P.W. 2013. Expression and mapping of anthocyanin biosynthesis genes in carrot. Theoretical and Applied Genetics. 126(7):1689-1702. Interpretive Summary: Most carrots today are orange in color, but until about 1500 purple carrots were common. This color is due to pigments called anthocyanins, and they are synthesized by the anthocyanin biochemical pathway, which includes over 20 enzymes. In past research we had discovered that one gene, called P1, is responsible for purple carrot root color. In this research we located the P1, gene on the carrot genetic map, and we also evaluated the expression and genetic map location of six enzymes of the anthocyanin pathway. We discovered that five of the six anthocyanin biosynthetic genes are much more active in purple carrots than in carrots that do no accumulate anthocyanins. Two of the six anthocyanin biosynthetic genes are on the same chromosome as the P1, gene. This information is of interest to plant geneticists and biochemists, and to carrot breeders.
Technical Abstract: Anthocyanin gene expression has been extensively studied in leaves, fruits and flowers of numerous plants. Little, however, is known about anthocyanin accumulation in roots, or in carrots or other Apiaceae. We quantified expression of six anthocyanin biosynthetic genes (phenylalanine ammonia-lyase (PAL3), chalcone synthase (CHS1), flavanone 3-hydroxylase (F3H), dihydroflavonol 4-reductase (DFR1), leucoanthocyanidin dioxygenase (LDOX2), and UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGT)) in three carrot inbreds with contrasting root color: solid purple (phloem and xylem); purple outer phloem/orange xylem; and orange phloem and xylem. Transcripts for five of these genes (PAL3, CHS1, F3H, DFR1, LDOX2) accumulated at high levels in solid purple carrots, less in purple orange carrot, and low or no transcript in orange carrots. Gene expression coincided with anthocyanin accumulation. In contrast, UFGT expression was comparable in purple and orange carrots, and relatively unchanged during root development. We genetically mapped five of the anthocyanin biosynthesis genes (FLS1 (flavonol synthase), DFR1, F3H, LDOX2, and PAL3) and two anthocyanin transcription factors (DcMYB3 and DcMYB5) in a population segregating for the P1 locus that conditions purple storage root color. The F3H and FLS1 genes were < 1 cM apart on chromosome 3, and < 3 cM from P1, while LDOX2 and PAL3 were unlinked to P1. The gene expression and mapping data suggests a coordinated regulatory control of anthocyanin expression in carrot root and establish a framework for studying the anthocyanin pathway in carrots, and they also suggest that none of the genes evaluated is a candidate for P1.