Enhancing ascorbate in fruits and tubers through over-expression of the l-galactose pathway gene GDP-l-galactose phosphorylase
Article first published online: 1 DEC 2011
© 2011 The Authors. Plant Biotechnology Journal © 2011 Society for Experimental Biology, Association of Applied Biologists and Blackwell Publishing Ltd
Plant Biotechnology Journal
Volume 10, Issue 4, pages 390–397, May 2012
How to Cite
Bulley, S., Wright, M., Rommens, C., Yan, H., Rassam, M., Lin-Wang, K., Andre, C., Brewster, D., Karunairetnam, S., Allan, A. C. and Laing, W. A. (2012), Enhancing ascorbate in fruits and tubers through over-expression of the l-galactose pathway gene GDP-l-galactose phosphorylase. Plant Biotechnology Journal, 10: 390–397. doi: 10.1111/j.1467-7652.2011.00668.x
- Issue published online: 2 APR 2012
- Article first published online: 1 DEC 2011
- Received 10 August 2011;revised 24 October 2011;accepted 26 October 2011.
- genetic engineering;
Ascorbate, or vitamin C, is obtained by humans mostly from plant sources. Various approaches have been made to increase ascorbate in plants by transgenic means. Most of these attempts have involved leaf material from model plants, with little success reported using genes from the generally accepted l-galactose pathway of ascorbate biosynthesis. We focused on increasing ascorbate in commercially significant edible plant organs using a gene, GDP-l-galactose phosphorylase (GGP or VTC2), that we had previously shown to increase ascorbate concentration in tobacco and Arabidopsis thaliana. The coding sequence of Actinidia chinensis GGP, under the control of the 35S promoter, was expressed in tomato and strawberry. Potato was transformed with potato or Arabidopsis GGP genes under the control of the 35S promoter or a polyubiquitin promoter (potato only). Five lines of tomato, up to nine lines of potato, and eight lines of strawberry were regenerated for each construct. Three lines of tomato had a threefold to sixfold increase in fruit ascorbate, and all lines of strawberry showed a twofold increase. All but one line of each potato construct also showed an increase in tuber ascorbate of up to threefold. Interestingly, in tomato fruit, increased ascorbate was associated with loss of seed and the jelly of locular tissue surrounding the seed which was not seen in strawberry. In both strawberry and tomato, an increase in polyphenolic content was associated with increased ascorbate. These results show that GGP can be used to raise significantly ascorbate concentration in commercially significant edible crops.