title: Evaluation of transgenic tomato plants expressing an additional phytoene synthase in a fruit-specific manner.
abstract: Phytoene synthase from the bacterium Erwinia uredovora (crtB) has been overexpressed in tomato (Lycopersicon esculentum Mill. cv. Ailsa Craig). Fruit-specific expression was achieved by using the tomato polygalacturonase promoter, and the CRTB protein was targeted to the chromoplast by the tomato phytoene synthase-1 transit sequence. Total fruit carotenoids of primary transformants (T(0)) were 2-4-fold higher than the controls, whereas phytoene, lycopene, beta-carotene, and lutein levels were increased 2.4-, 1.8-, and 2.2-fold, respectively. The biosynthetically related isoprenoids, tocopherols plastoquinone and ubiquinone, were unaffected by changes in carotenoid levels. The progeny (T(1) and T(2) generations) inherited both the transgene and phenotype. Determination of enzyme activity and Western blot analysis revealed that the CRTB protein was plastid-located and catalytically active, with 5-10-fold elevations in total phytoene synthase activity. Metabolic control analysis suggests that the presence of an additional phytoene synthase reduces the regulatory effect of this step over the carotenoid pathway. The activities of other enzymes in the pathway (isopentenyl diphosphate isomerase, geranylgeranyl diphosphate synthase, and incorporation of isopentenyl diphosphate into phytoene) were not significantly altered by the presence of the bacterial phytoene synthase.
authors.affiliation: School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 OEX, United Kingdom.
authors.forename: Paul D
authors.initials: PD
authors.lastname: Fraser
authors.forename: Susanne
authors.initials: S
authors.lastname: Romer
authors.forename: Cathie A
authors.initials: CA
authors.lastname: Shipton
authors.forename: Philippa B
authors.initials: PB
authors.lastname: Mills
authors.forename: Joy W
authors.initials: JW
authors.lastname: Kiano
authors.forename: Norihiko
authors.initials: N
authors.lastname: Misawa
authors.forename: Rachel G
authors.initials: RG
authors.lastname: Drake
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schuch
authors.forename: Peter M
authors.initials: PM
authors.lastname: Bramley
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics*; D002338:Carotenoids / Q000378:metabolism; D015870:Gene Expression; D005798:Genes, Bacterial; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase; D018551:Solanum lycopersicum / Q000201:enzymology* / Q000235:genetics* / Q000378:metabolism; D016973:Pectobacterium carotovorum / Q000201:enzymology / Q000235:genetics; D030821:Plants, Genetically Modified; D014018:Tissue Distribution
chemical_list: D002338:Carotenoids; D019883:Alkyl and Aryl Transferases; D051232:Geranylgeranyl-Diphosphate Geranylgeranyltransferase