Alterations in Ascorbic Acid Levels by Transformation of the L-galactono-1,4-lactone Dehydrogenase Gene in Solanum tuberosum

Abstract

L-galactono-1, 4-lactone dehydrogenase (GLDH) is an important enzyme that catalyzes the last step of the ascorbate biosynthetic pathways in plants. A full-length cDNA clone encoding GLDH was isolated from potato (Solanum tuberosum L. ‘Favorita’) leaf and subcloned into a binary vector, pBI121, to construct sense and antisense recombinant plant expression vectors. The recombinants were introduced into potato via Agrobacterium-mediated transformation, and plants were confirmed as transgenic using PCR and quantitative real-time PCR. Two anti-sense potato lines (G1 and G2) and three sense lines (G3, G4 and G5) were obtained. The GLDH activity of G4 and G5 were increased in vivo. Moreover, the ascorbic acid (AsA) and dehydroascorbate (DHA) contents were up-regulated in both leaves and tubers. However, the shoots of G1 were suppressed and its leaves were deformed. Additionally, the AsA contents in G1 leaves and tubers decreased by 28.8% and 10.3%, respectively. The GLDH activity in leaves treated with L-galactono-1,4-lactone (L-GalL) increased in all lines, as did the AsA and DHA contents. These results indicate that GLDH activity plays an important role in regulating the AsA level as well as the growth and development of potato plants.