title: Regulation of L-ascorbic acid content in strawberry fruits.
abstract: Plants have several L-ascorbic acid (AsA) biosynthetic pathways, but the contribution of each one to the synthesis of AsA varyies between different species, organs, and developmental stages. Strawberry (Fragaria×ananassa) fruits are rich in AsA. The pathway that uses D-galacturonate as the initial substrate is functional in ripe fruits, but the contribution of other pathways to AsA biosynthesis has not been studied. The transcription of genes encoding biosynthetic enzymes such as D-galacturonate reductase (FaGalUR) and myo-inositol oxygenase (FaMIOX), and the AsA recycling enzyme monodehydroascorbate reductase (FaMDHAR) were positively correlated with the increase in AsA during fruit ripening. Fruit storage for 72 h in a cold room reduced the AsA content by 30%. Under an ozone atmosphere, this reduction was 15%. Ozone treatment increased the expression of the FaGalUR, FaMIOX, and L-galactose-1-phosphate phosphatase (FaGIPP) genes, and transcription of the L-galactono-1,4-lactone dehydrogenase (FaGLDH) and FAMDHAR genes was higher in the ozone-stored than in the air-stored fruits. Analysis of AsA content in a segregating population from two strawberry cultivars showed high variability, which did not correlate with the transcription of any of the genes studied. Study of GalUR protein in diverse cultivars of strawberry and different Fragaria species showed that a correlation between GalUR and AsA content was apparent in most cases, but it was not general. Three alleles were identified in strawberry, but any sequence effect on the AsA variability was eliminated by analysis of the allele-specific expression. Taken together, these results indicate that FaGalUR shares the control of AsA levels with other enzymes and regulatory elements in strawberry fruit.
authors.affiliation: Instituto de Hortofruticultura Subtropical y Mediterránea, Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Departamento de Biología Molecular y Bioquímica, Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos s/n, E-29071 Málaga, Spain.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Cruz-Rus
authors.forename: Iraida
authors.initials: I
authors.lastname: Amaya
authors.forename: José F
authors.initials: JF
authors.lastname: Sánchez-Sevilla
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Botella
authors.forename: Victoriano
authors.initials: V
authors.lastname: Valpuesta
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D001205:Ascorbic Acid / Q000096:biosynthesis / Q000378:metabolism*; D001483:Base Sequence; D053898:Biosynthetic Pathways / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D031985:Fragaria / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D005638:Fruit / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D064430:NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D018744:DNA, Plant; D010940:Plant Proteins; D012333:RNA, Messenger; D000429:Alcohol Oxidoreductases; D064430:NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases; C477073:D-galacturonate reductase; D001205:Ascorbic Acid