title: Carotenoid isomerase is key determinant of petal color of Calendula officinalis.
abstract: Orange petals of calendula (Calendula officinalis) accumulate red carotenoids with the cis-configuration at the C-5 or C-5' position (5-cis-carotenoids). We speculated that the orange-flowered calendula is a carotenoid isomerase (crtiso) loss-of-function mutant that impairs the cis-to-trans conversion of 5-cis-carotenoids. We compared the sequences and enzyme activities of CRTISO from orange- and yellow-flowered calendulas. Four types of CRTISO were expressed in calendula petals. The deduced amino acid sequence of one of these genes (CoCRTISO1) was different between orange- and yellow-flowered calendulas, whereas the sequences of the other three CRTISOs were identical between these plants. Analysis of the enzymatic activities of the CoCRTISO homologs showed that CoCRTISO1-Y, which was expressed in yellow petals, converted carotenoids from the cis-to-trans-configuration, whereas both CoCRTISO1-ORa and 1-ORb, which were expressed in orange petals, showed no activity with any of the cis-carotenoids we tested. Moreover, the CoCRTISO1 genotypes of the F2 progeny obtained by crossing orange and yellow lines linked closely to petal color. These data indicate that CoCRTISO1 is a key regulator of the accumulation of 5-cis-carotenoids in calendula petals. Site-directed mutagenesis showed that the deletion of Cys-His-His at positions 462-464 in CoCRTISO1-ORa and a Gly-to-Glu amino acid substitution at position 450 in CoCRTISO1-ORb abolished enzyme activity completely, indicating that these amino acid residues are important for the enzymatic activity of CRTISO.
authors: National Institute of Floricultural Science, National Agriculture and Food Research Organization, Fujimoto 2-1, Tsukuba, Ibaraki 305-8519, Japan.
authors: Sanae
authors: S
authors: Kishimoto
authors: National Institute of Floricultural Science, National Agriculture and Food Research Organization, Fujimoto 2-1, Tsukuba, Ibaraki 305-8519, Japan. Electronic address: ohmiya@affrc.go.jp.
authors: Akemi
authors: A
authors: Ohmiya
mesh_terms: D000595:Amino Acid Sequence; D020838:Calendula / Q000033:anatomy & histology* / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D002338:Carotenoids / Q000378:metabolism*; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant; D005838:Genotype; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010858:Pigmentation; D018515:Plant Leaves / Q000033:anatomy & histology* / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D019745:cis-trans-Isomerases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D002338:Carotenoids; D019745:cis-trans-Isomerases