title: Tyrosine Hydroxylation in Betalain Pigment Biosynthesis Is Performed by Cytochrome P450 Enzymes in Beets (Beta vulgaris).
abstract: Yellow and red-violet betalain plant pigments are restricted to several families in the order Caryophyllales, where betacyanins play analogous biological roles to anthocyanins. The initial step in betalain biosynthesis is the hydroxylation of tyrosine to form L-DOPA. Using gene expression experiments in beets, yeast, and Arabidopsis, along with HPLC/MS analysis, the present study shows that two novel cytochrome P450 (CYP450) enzymes, CYP76AD6 and CYP76AD5, and the previously described CYP76AD1 can perform this initial step. Co-expressing these CYP450s with DOPA 4,5-dioxygenase in yeast, and overexpression of these CYP450s in yellow beets show that CYP76AD1 efficiently uses L-DOPA leading to red betacyanins while CYP76AD6 and CYP76AD5 lack this activity. Furthermore, CYP76AD1 can complement yellow beetroots to red while CYP76AD6 and CYP76AD5 cannot. Therefore CYP76AD1 uniquely performs the beet R locus function and beets appear to be genetically redundant for tyrosine hydroxylation. These new functional data and ancestral character state reconstructions indicate that tyrosine hydroxylation alone was the most likely ancestral function of the CYP76AD alpha and beta groups and the ability to convert L-DOPA to cyclo-DOPA evolved later in the alpha group.
authors.affiliation: Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America.
authors.forename: Rasika
authors.initials: R
authors.lastname: Sunnadeniya
authors.affiliation: Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America.
authors.forename: Alexander
authors.initials: A
authors.lastname: Bean
authors.affiliation: Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America.
authors.forename: Matthew
authors.initials: M
authors.lastname: Brown
authors.affiliation: Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America.
authors.forename: Neda
authors.initials: N
authors.lastname: Akhavan
authors.affiliation: Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America.
authors.forename: Gregory
authors.initials: G
authors.lastname: Hatlestad
authors.affiliation: Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America.
authors.forename: Antonio
authors.initials: A
authors.lastname: Gonzalez
authors.affiliation: Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
authors.forename: V Vaughan
authors.initials: VV
authors.lastname: Symonds
authors.affiliation: Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, United States of America.
authors.forename: Alan
authors.initials: A
authors.lastname: Lloyd
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D027461:Beta vulgaris / Q000235:genetics / Q000378:metabolism*; D050859:Betacyanins / Q000096:biosynthesis; D050858:Betalains / Q000096:biosynthesis* / Q000737:chemistry; D017124:Conserved Sequence; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D020869:Gene Expression Profiling; D006900:Hydroxylation / Q000235:genetics; D007980:Levodopa / Q000378:metabolism; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D056510:Position-Specific Scoring Matrices; D014443:Tyrosine / Q000378:metabolism*
chemical_list: D050859:Betacyanins; D050858:Betalains; D014443:Tyrosine; D007980:Levodopa; D003577:Cytochrome P-450 Enzyme System; D010105:Oxygenases