title: Isolation and functional characterization of a lycopene beta-cyclase gene that controls fruit colour of papaya (Carica papaya L.).
abstract: The colour of papaya fruit flesh is determined largely by the presence of carotenoid pigments. Red-fleshed papaya fruit contain lycopene, whilst this pigment is absent from yellow-fleshed fruit. The conversion of lycopene (red) to beta-carotene (yellow) is catalysed by lycopene beta-cyclase. This present study describes the cloning and functional characterization of two different genes encoding lycopene beta-cyclases (lcy-beta1 and lcy-beta2) from red (Tainung) and yellow (Hybrid 1B) papaya cultivars. A mutation in the lcy-beta2 gene, which inactivates enzyme activity, controls lycopene production in fruit and is responsible for the difference in carotenoid production between red and yellow-fleshed papaya fruit. The expression level of both lcy-beta1 and lcy-beta2 genes is similar and low in leaves, but lcy-beta2 expression increases markedly in ripe fruit. Isolation of the lcy-beta2 gene from papaya, that is preferentially expressed in fruit and is correlated with fruit colour, will facilitate marker-assisted breeding for fruit colour in papaya and should create possibilities for metabolic engineering of carotenoid production in papaya fruit to alter both colour and nutritional properties.
authors.affiliation: Department of Employment, Economic Development and Innovation (DEEDI), Primary Industries and Fisheries, Queensland Agricultural Biotechnology Centre, PO Box 6097, Australia.
authors.forename: Luke C
authors.initials: LC
authors.lastname: Devitt
authors.forename: Kent
authors.initials: K
authors.lastname: Fanning
authors.forename: Ralf G
authors.initials: RG
authors.lastname: Dietzgen
authors.forename: Timothy A
authors.initials: TA
authors.lastname: Holton
mesh_terms: D000483:Alleles; D029441:Carica / Q000201:enzymology* / Q000235:genetics*; D002851:Chromatography, High Pressure Liquid; D004926:Escherichia coli; D005638:Fruit / Q000201:enzymology* / Q000235:genetics*; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D019753:Intramolecular Lyases / Q000235:genetics*; D053858:Metabolic Networks and Pathways; D008969:Molecular Sequence Data; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D019753:Intramolecular Lyases; C070925:lycopene cyclase-isomerase