Light- and ascorbate-dependent regulation of VITAMIN C DEFECTIVE 2 protein expression in Arabidopsis

Ascorbate accumulation under light conditions is regulated by GDP-L-galactose phosphorylase (GGP), which catalyzes the rate-limiting step in the ascorbate biosynthesis pathway and is encoded by the Vitamin C Defective 2 (VTC2). While the VTC2 gene expression and the GGP activity in response to light have been extensively studied, the behavior of the VTC2 protein remains unclear. To explore the role of VTC2 protein accumulation in modulating ascorbate biosynthesis, we generated transgenic plants expressing VTC2 fused with a Myc tag, driven by the native VTC2 promoter, within vtc2-4 lacking VTC2. Under normal light conditions, VTC2 transcripts, VTC2 protein levels, and GGP activity exhibited an increase during the early light period. These data highlight the importance of VTC2 protein accumulation during the early light phase in determining ascorbate biosynthesis capacity in response to light. Furthermore, our analysis demonstrated that high-ascorbate concentrations suppress VTC2 expression.