title: Transient expression analysis revealed the importance of VTC2 expression level in light/dark regulation of ascorbate biosynthesis in Arabidopsis.
abstract: Ascorbate (AsA) is an important antioxidant and an enzyme cofactor involved in various metabolic pathways. In this study, we investigated the effects of estrogen (ES)-inducible transient expression of genes encoding enzymes involved in the d-mannose/l-galactose (d-Man/l-Gal) pathway for plant AsA biosynthesis on AsA levels under light and dark conditions. No significant difference was observed in AsA levels between Arabidopsis plants transiently expressing phosphomannose isomerase (PMI1), GDP-d-Man pyrophosphorylase (GMP/VTC1), GDP-Man-3',5'-epimerase (GME), and l-Gal 1-phosphate phosphatase (GPP/VTC4), but AsA levels in the plants transiently expressing GDP-l-Gal phosphorylase (GGP/VTC2) were 2.5-fold higher than those in control plants 7 d after ES treatment. The increase in AsA levels under continuous light conditions and the decrease in AsA levels under dark conditions were enhanced and suppressed, respectively, in the ES-treated plants. These results suggest that GGP/VTC2 acts as a rate-limiting step regulating AsA biosynthesis in response to light and dark conditions.
authors.affiliation: a Department of Food and Nutritional Science, College of Bioscience and Biotechnology , Chubu University , Kasugai , Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Yoshimura
authors.forename: Tomono
authors.initials: T
authors.lastname: Nakane
authors.forename: Seina
authors.initials: S
authors.lastname: Kume
authors.forename: Yuki
authors.initials: Y
authors.lastname: Shiomi
authors.forename: Takanori
authors.initials: T
authors.lastname: Maruta
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishikawa
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shigeoka
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001205:Ascorbic Acid / Q000096:biosynthesis* / Q000378:metabolism; D055162:Biocatalysis; D003624:Darkness; D004967:Estrogens / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects / Q000528:radiation effects; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics* / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D004967:Estrogens; C522629:GDP-L-galactose phosphorylase, Arabidopsis; D010744:Phosphoric Monoester Hydrolases; D001205:Ascorbic Acid
keywords: GDP-l-galactose phosphorylase; VTC2; ascorbate; biosynthesis; light and dark regulation