title: Molecular characterization and expression studies during melon fruit development and ripening of L-galactono-1,4-lactone dehydrogenase.
abstract: The last step of ascorbic acid (AA) biosynthesis is catalysed by the enzyme L-galactono-1,4-lactone dehydrogenase (GalLDH, EC 1.3.2.3), located on the inner mitochondrial membrane. The enzyme converts L-galactono-1,4-lactone to ascorbic acid (AA). In this work, the cloning and characterization of a GalLDH full-length cDNA from melon (Cucumis melo L.) are described. Melon genomic DNA Southern analysis indicated that CmGalLDH was encoded by a single gene. CmGalLDH mRNA accumulation was detected in all tissues studied, but differentially expressed during fruit development and seed germination. It is hypothesized that induction of CmGalLDH gene expression in ripening melon fruit contributes to parallel increases in the AA content and so playing a role in the oxidative ripening process. Higher CmGalLDH message abundance in light-grown seedlings compared with those raised in the dark suggests that CmGalLDH expression is regulated by light. Finally, various stresses and growth regulators resulted in no significant change in steady state levels of CmGalLDH mRNA in 20-d-old melon seedlings. To the authors' knowledge, this is the first report of GalLDH transcript induction in seed germination and differential gene expression during fruit ripening.
authors.affiliation: Group of Biotechnology of Pharmaceutical Plants, Laboratory of Pharmacognocy, Department of Pharmaceutical Sciences, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece.
authors.forename: Irene
authors.initials: I
authors.lastname: Pateraki
authors.forename: Maite
authors.initials: M
authors.lastname: Sanmartin
authors.forename: Mary S
authors.initials: MS
authors.lastname: Kalamaki
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Gerasopoulos
authors.forename: Angelos K
authors.initials: AK
authors.lastname: Kanellis
mesh_terms: D000595:Amino Acid Sequence; D001205:Ascorbic Acid / Q000032:analysis / Q000096:biosynthesis; D003001:Cloning, Molecular; D028463:Cucumis melo / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D005638:Fruit / Q000235:genetics / Q000254:growth & development*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D044925:Oxidoreductases Acting on CH-CH Group Donors; C093910:galactonolactone dehydrogenase; D001205:Ascorbic Acid