Cloning and gene expression analysis of ascorbic acid biosynthesis enzymes in Moringa oleifera

Moringa (Moringa oleifera), which is a semi-tropical plant, is used as food and for the production of medicines and oil products, because of a large amount of various nutrients including ascorbic acid (AsA). Although Moringa leaf has a high AsA content, the molecular mechanisms of AsA accumulation in Moringa have received little attention. In this study, we isolated Moringa cDNAs for enzymes, belonging to the major AsA biosynthesis pathway (Smirnoff-Wheeler pathway) in higher plants. The predicted amino acid sequences showed 70% or more similarity to those of Arabidopsis. Quantitative RT-PCR indicated that Moringa GDP-L-galactose phosphorylase (GGP) is most highly expressed in Moringa during leaf development and light exposure. A significant high promoter activity of the Moringa GGP gene was detected by promoter assay in Arabidopsis protoplast.   Key words: Moringa oleifera, ascorbic acid, biosynthesis enzymes, gene expression.