Abstract
VTC2 and VTC5 genes, encoding GDP-L-galactose phosphorylase, play a central role of D-mannose/L-galactose pathway for ascorbic acid (AsA) biosynthesis in Arabidopsis thaliana (Plant J., 2007; JXB, 2007). In this study, we focus on the analysis of the VTC2 and VTC5 gene expression levels under illumination and germination, affecting cellular AsA contents. The AsA level in mature green leaves exhibited a diurnal rhythm and the expression of VTC2 increased after illumination, while the expression of VTC5 was much less than that of VTC2. At the very early growth stage after sprouting, the expression level of VTC2 was approximately two fold higher than that of VTC5. In the promoter::LUC transformed lines, at different seedling stages, the luminescence signals were consistent with the expression data obtained by quantitative PCR. These results suggest that VTC2 dominantly contributes to AsA supply in all the stage of plant growth and light environment, and VTC5 may compensate the function of VTC2 in germination period.
