title: Increased antioxidant capacity in tomato by ectopic expression of the strawberry D-galacturonate reductase gene.
abstract: Increasing L-ascorbic acid (AsA, vitamin C) content in fruits is a common goal in current breeding programs due to its beneficial effect on human health. Attempts to increase AsA content by genetic engineering have resulted in variable success likely due to AsA's complex regulation. Here, we report the effect of ectopically expressing in tomato the D-galacturonate reductase (FaGalUR) gene from strawberry, involved in AsA biosynthesis, either under the control of the constitutive 35S or the tomato fruit-specific polygalucturonase (PG) promoters. Although transgenic lines showed a moderate increase on AsA content, complex changes in metabolites were found in transgenic fruits. Metabolomic analyses of ripe fruits identified a decrease in citrate, glutamate, asparagine, glucose, and fructose, accompanied by an increase of sucrose, galactinol, and chlorogenic acid. Significant metabolic changes also occurred in leaves of 35S-FaGalUR lines, which showed higher non-photochemical fluorescence quenching (NPQ), indicative of a higher constitutive photo-protective capacity. Overall, overexpression of FaGalUR increased total antioxidant capacity in fruits and the results suggest a tight control of AsA content, probably linked to a complex regulation of cellular redox state and metabolic adjustment.
authors.affiliation: Instituto Andaluz de Investigación y Formación Agraria y Pesquera (IFAPA), Centro de Churriana, Málaga, Spain.
authors.forename: Iraida
authors.initials: I
authors.lastname: Amaya
authors.forename: Sonia
authors.initials: S
authors.lastname: Osorio
authors.forename: Elsa
authors.initials: E
authors.lastname: Martinez-Ferri
authors.forename: Viviana
authors.initials: V
authors.lastname: Lima-Silva
authors.forename: Veronica G
authors.initials: VG
authors.lastname: Doblas
authors.forename: Rafael
authors.initials: R
authors.lastname: Fernández-Muñoz
authors.forename: Alisdair R
authors.initials: AR
authors.lastname: Fernie
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Botella
authors.forename: Victoriano
authors.initials: V
authors.lastname: Valpuesta
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D001205:Ascorbic Acid / Q000378:metabolism; D000066630:Ectopic Gene Expression; D031985:Fragaria / Q000201:enzymology*; D005638:Fruit / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D006801:Humans; D018551:Solanum lycopersicum / Q000235:genetics* / Q000378:metabolism; D055432:Metabolomics / Q000379:methods; D064430:NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000378:metabolism*; D011401:Promoter Regions, Genetic
chemical_list: D000975:Antioxidants; D064430:NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases; C477073:D-galacturonate reductase; D001205:Ascorbic Acid
keywords: Antioxidants; Ascorbic acid; Galacturonate reductase; Redox; Solanum lycopersicum