title: Color genes in the orchid Oncidium Gower Ramsey: identification, expression, and potential genetic instability in an interspecific cross.
abstract: Orchids are one of the most unique and evolved of flowering plants, with many being valuable floricultural crops. Spatial localization of pigments within the flower of the commercially important bi-color Oncidium Gower Ramsey demonstrated a mixture of carotenoids and anthocyanins concentrated in the adaxial epidermis. Chromatography identified the predominant yellow pigment to be an equal mixture of all-trans and 9-cis isomers of violaxanthin, with esterification specific to the 9-cis isomer. Red ornamentation was comprised of the anthocyanins cyanidin and its methylated derivate, peonidin. Five key pigment biosynthesis genes encoding dihydroflavonol 4-reductase (DFR), phytoene synthase (PSY), phytoene desaturase, carotenoid isomerase, and the downstream 9-cis epoxycarotenoid dioxygenase were isolated and their expression profiles determined. Northern analyses showed both phytoene desaturase and carotenoid isomerase expression to be up-regulated in floral tissue relative to leaves whereas PSY was not. Three closely related DFR genes were isolated, including one with an insertion in the 3' coding region. DFR expression occurred throughout flower development in Oncidium, unlike in Dendrobium and Bromheadia orchids. A number of the isolated anthocyanin and carotenoid genes showed variations due to insertion events. These findings raise questions about the genetic stability in interspecific crosses in orchids, such as the tri-specific Oncidium Gower Ramsey.
authors.affiliation: Department of Tropical Plant and Soil Sciences, University of Hawaii at Manoa, 3190 Maile Way, St. John Rm 102, Honolulu, HI 96822, USA. hieber@hawaii.edu
authors.forename: A David
authors.initials: AD
authors.lastname: Hieber
authors.forename: Rasika G
authors.initials: RG
authors.lastname: Mudalige-Jayawickrama
authors.forename: Adelheid R
authors.initials: AR
authors.lastname: Kuehnle
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D019883:Alkyl and Aryl Transferases / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000872:Anthocyanins / Q000032:analysis / Q000096:biosynthesis* / Q000302:isolation & purification; D001483:Base Sequence; D002338:Carotenoids / Q000032:analysis / Q000096:biosynthesis* / Q000302:isolation & purification; D003433:Crosses, Genetic; D049308:Dioxygenases; D017343:Genes, Plant; D042822:Genomic Instability; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase; D007535:Isomerases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D029595:Orchidaceae / Q000033:anatomy & histology / Q000201:enzymology / Q000235:genetics*; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism; D010858:Pigmentation; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment
chemical_list: D000872:Anthocyanins; D010940:Plant Proteins; D002338:Carotenoids; D010088:Oxidoreductases; D000429:Alcohol Oxidoreductases; C056570:dihydroflavanol 4-reductase; D010105:Oxygenases; D049308:Dioxygenases; C109043:9-cis-epoxy-carotenoid dioxygenase; C022398:phytoene dehydrogenase; D019883:Alkyl and Aryl Transferases; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase; D007535:Isomerases