|Mcgrath, J Mitchell - Mitch|
Submitted to: Transgenic Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2007
Publication Date: 4/1/2008
Citation: Crowell, E.F., McGrath, J.M., Douches, D. 2008. Accumulation of vitamin E in potato (Solanum tuberosom) tubers. Transgenic Research. 17(2):205-217.
Interpretive Summary: Vitamin E is essential for human health and is synthesized only by plants. Genetic approaches were followed to examine Vitamin E in potato tubers and to evaluate whether they might be increased using modern genetic tools. Results showed that Vitamin E levels in potato tubers were small, relative to potato leaves, and that changing the expression of two key enzymes in Vitamin E biosynthesis from leaves to tubers resulted in a marginal improvement of Vitamin E levels in the potato tuber. This research is the first to demonstrate that Vitamin E levels in the fresh potato can be genetically improved, and will stimulate further research to provide potatoes to consumers with nutritionally significant levels of Vitamin E from potatoes.
Technical Abstract: Vitamin E (tocopherol) is a powerful antioxidant essential for human health and synthesized only by photosynthetic organisms. The effects of overexpression of tocopherol biosynthetic enzymes have been studied in leaves and seeds, but not in a non-photosynthetic, below-ground plant organ. Genetic and molecular approaches were used to determine if increased levels of tocopherols can be accumulated in potato (Solanum tuberosum L.) tubers through metabolic engineering. Two transgenes were constitutively overexpressed in potato: Arabidopsis thaliana p-hydroxyphenylpyruvate dioxygenase (At-HPPD) and A. thaliana homogentisate phytyltransferase (At-HPT). Alpha-Tocopherol levels in the transgenic plants were determined by high performance liquid chromatography (HPLC). In potato tubers, overexpression of At-HPPD resulted in a maximum 266% increase in alpha-tocopherol, and overexpression of At-HPT yielded a 106% increase. However, tubers from transgenic plants still accumulated approximately 10- and 100-fold less alpha-tocopherol than leaves or seeds, respectively. The results indicate that physiological and regulatory constraints may be the most limiting factors for tocopherol accumulation in potato tubers. Studying regulation and induction of tocopherol biosynthesis should reveal approaches to more effectively engineer crops with enhanced tocopherol content.