title: Elucidation of the first committed step in betalain biosynthesis enables the heterologous engineering of betalain pigments in plants.
abstract: Betalains are tyrosine-derived red-violet and yellow pigments, found in plants only of the Caryophyllales order. Although much progress has been made in recent years in the understanding of the betalain biosynthetic process, many questions remain open with regards to several of the proposed steps in the pathway. Most conspicuous by its absence is the characterization of the first committed step in the pathway, namely the 3-hydroxylation of tyrosine to form l-3,4-dihydroxyphenylalanine (l-DOPA). We used transcriptome analysis of the betalain-producing plants red beet (Beta vulgaris) and four o'clocks (Mirabilis jalapa) to identify a novel, betalain-related cytochrome P450-type gene, CYP76AD6, and carried out gene silencing and recombinant expression assays in Nicotiana benthamiana and yeast cells to examine its functionality. l-DOPA formation in red beet was found to be redundantly catalyzed by CYP76AD6 together with a known betalain-related enzyme, CYP76AD1, which was previously thought to only catalyze a succeeding step in the pathway. While CYP76AD1 catalyzes both l-DOPA formation and its subsequent conversion to cyclo-DOPA, CYP76AD6 uniquely exhibits only tyrosine hydroxylase activity. The new findings enabled us to metabolically engineer entirely red-pigmented tobacco plants through heterologous expression of three genes taking part in the fully decoded betalain biosynthetic pathway.
authors.affiliation: Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: Guy
authors.initials: G
authors.lastname: Polturak
authors.affiliation: Department of Metabolic Biology, John Innes Centre, Norwich, NR4 7UH, UK.
authors.forename: Dario
authors.initials: D
authors.lastname: Breitel
authors.affiliation: Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: Noam
authors.initials: N
authors.lastname: Grossman
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas, Universidad Politécnica de Valencia, Valencia, 46022, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Sarrion-Perdigones
authors.affiliation: Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: Efrat
authors.initials: E
authors.lastname: Weithorn
authors.affiliation: Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: Margarita
authors.initials: M
authors.lastname: Pliner
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas, Universidad Politécnica de Valencia, Valencia, 46022, Spain.
authors.forename: Diego
authors.initials: D
authors.lastname: Orzaez
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas, Universidad Politécnica de Valencia, Valencia, 46022, Spain.
authors.forename: Antonio
authors.initials: A
authors.lastname: Granell
authors.affiliation: Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: Ilana
authors.initials: I
authors.lastname: Rogachev
authors.affiliation: Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, 7610001, Israel.
authors.forename: Asaph
authors.initials: A
authors.lastname: Aharoni
mesh_terms: D027461:Beta vulgaris / Q000235:genetics*; D050859:Betacyanins / Q000096:biosynthesis; D050858:Betalains / Q000096:biosynthesis* / Q000737:chemistry; D050860:Betaxanthins / Q000096:biosynthesis; D053898:Biosynthetic Pathways / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004295:Dihydroxyphenylalanine / Q000096:biosynthesis; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D005818:Genetic Engineering / Q000379:methods*; D039282:Mirabilis / Q000235:genetics*; D010641:Phenotype; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics; D030821:Plants, Genetically Modified; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics
chemical_list: D050859:Betacyanins; D050860:Betaxanthins; D011994:Recombinant Proteins; D050858:Betalains; D004295:Dihydroxyphenylalanine; D003577:Cytochrome P-450 Enzyme System
keywords: Beta vulgaris; betalains; gene function; pigments; plant metabolic engineering; secondary metabolism