The invention provides compositions and methods for modulating GDP-L-Galactose Guanyltransferase (also known as GDP-L-Galactose phosphorylase) activity; and/or GDP-D-Mannose epimerase activity; and/or ascorbate content in plants. The invention provides plants and plant cells with increased GDP-L-Galactose Guanyltransferase activity; and/or GDP-D-Mannose epimerase activity. The invention provides plants and plant cells with increased ascorbate content as a result of: over-expression of GDP-L-Galactose Guanyltransferase; over-expression of GDP-D-Mannose epimerase; or in particular over-expression of a combination of GDP-L-Galactose Guanyltransferase and GDP-D-Mannose epimerase.