Transient expression analysis revealed the importance of VTC2 expression level in light/dark regulation of ascorbate
Kazuya Yoshimura1, Tomono Nakane, Seina Kume
1a Department of Food and Nutritional Science, College of Bioscience and Biotechnology , Chubu University , Kasugai , Japan.
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.
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