The regulation of ascorbate biosynthesis

[Display omitted] •Ascorbate is an essential reductant/antioxidant in plants.•The concentration of ascorbate varies between plant tissues and different plants.•GDP-galactose phosphorylase is controlled translationally and transcriptionally.•Seven other genes that regulate ascorbate in Arabidopsis have been identified. We review the regulation of ascorbate (vitamin C) biosynthesis, focusing on the l-galactose pathway. We discuss the regulation of ascorbate biosynthesis at the level of gene transcription (both repression and enhancement) and translation (feedback inhibition of translation by ascorbate concentration) and discuss the eight proteins that have been demonstrated to date to affect ascorbate concentration in plant tissues. GDP-galactose phosphorylase (GGP) and GDP-mannose epimerase are critical steps that regulate ascorbate biosynthesis. These and other biosynthetic genes are controlled at the transcriptional level, while GGP is also controlled at the translational level. Ascorbate feedback on enzyme activity has not been observed unequivocally.