title: Temporal and spatial regulation of anthocyanin biosynthesis provide diverse flower colour intensities and patterning in Cymbidium orchid.
abstract: This study confirmed pigment profiles in different colour groups, isolated key anthocyanin biosynthetic genes and established a basis to examine the regulation of colour patterning in flowers of Cymbidium orchid. Cymbidium orchid (Cymbidium hybrida) has a range of flower colours, often classified into four colour groups; pink, white, yellow and green. In this study, the biochemical and molecular basis for the different colour types was investigated, and genes involved in flavonoid/anthocyanin synthesis were identified and characterised. Pigment analysis across selected cultivars confirmed cyanidin 3-O-rutinoside and peonidin 3-O-rutinoside as the major anthocyanins detected; the flavonols quercetin and kaempferol rutinoside and robinoside were also present in petal tissue. β-carotene was the major carotenoid in the yellow cultivars, whilst pheophytins were the major chlorophyll pigments in the green cultivars. Anthocyanin pigments were important across all eight cultivars because anthocyanin accumulated in the flower labellum, even if not in the other petals/sepals. Genes encoding the flavonoid biosynthetic pathway enzymes chalcone synthase, flavonol synthase, flavonoid 3' hydroxylase (F3'H), dihydroflavonol 4-reductase (DFR) and anthocyanidin synthase (ANS) were isolated from petal tissue of a Cymbidium cultivar. Expression of these flavonoid genes was monitored across flower bud development in each cultivar, confirming that DFR and ANS were only expressed in tissues where anthocyanin accumulated. Phylogenetic analysis suggested a cytochrome P450 sequence as that of the Cymbidium F3'H, consistent with the accumulation of di-hydroxylated anthocyanins and flavonols in flower tissue. A separate polyketide synthase, identified as a bibenzyl synthase, was isolated from petal tissue but was not associated with pigment accumulation. Our analyses show the diversity in flower colour of Cymbidium orchid derives not from different individual pigments but from subtle variations in concentration and pattern of pigment accumulation.
authors.affiliation: The New Zealand Institute for Plant and Food Research Limited, Private Bag 11 600, Palmerston North, 4474, New Zealand.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Nick W
authors.initials: NW
authors.lastname: Albert
authors.forename: Huaibi
authors.initials: H
authors.lastname: Zhang
authors.forename: Steve
authors.initials: S
authors.lastname: Arathoon
authors.forename: Murray R
authors.initials: MR
authors.lastname: Boase
authors.forename: Hanh
authors.initials: H
authors.lastname: Ngo
authors.forename: Kathy E
authors.initials: KE
authors.lastname: Schwinn
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Davies
authors.forename: David H
authors.initials: DH
authors.lastname: Lewis
mesh_terms: D000217:Acyltransferases / Q000145:classification / Q000235:genetics / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000872:Anthocyanins / Q000096:biosynthesis*; D053898:Biosynthetic Pathways; D002851:Chromatography, High Pressure Liquid; D003116:Color; D003577:Cytochrome P-450 Enzyme System / Q000145:classification / Q000235:genetics / Q000378:metabolism; D035264:Flowers / Q000235:genetics / Q000378:metabolism*; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D005960:Glucosides / Q000096:biosynthesis; D044949:Kaempferols / Q000096:biosynthesis; D013058:Mass Spectrometry; D029595:Orchidaceae / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D010088:Oxidoreductases / Q000145:classification / Q000235:genetics / Q000378:metabolism; D010105:Oxygenases / Q000145:classification / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics; D010940:Plant Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism; D011794:Quercetin / Q000096:biosynthesis; D013045:Species Specificity; D019207:beta Carotene / Q000096:biosynthesis
chemical_list: D000872:Anthocyanins; D005960:Glucosides; D044949:Kaempferols; D010940:Plant Proteins; C000597820:peonidin-3-rutinoside; D019207:beta Carotene; C006552:kaempferol; D003577:Cytochrome P-450 Enzyme System; D011794:Quercetin; D010088:Oxidoreductases; D000429:Alcohol Oxidoreductases; C056570:dihydroflavanol 4-reductase; D010105:Oxygenases; C038888:flavonoid 3'-hydroxylase; C118159:anthocyanidin synthase; C085313:flavonol synthase; D000217:Acyltransferases; C020141:flavanone synthetase; C428983:cyanidin 3-rutinoside