Poster: Metabolic engineering

Abs # 300: Metabolic engineering of vitamin E biosynthesis in oil seeds and photosynthetic bacteria

Presenter:	Karunanandaa, Balasulojini B, bbkaru@monsanto.com
Authors	Karunanandaa, Balasulojini B (A)   Qi, Qungang  (A)   Hao, Ming  (A)   Baszis, Susan  (A)   Jensen, Pamela  (A)   Wong, Yun-Hua  (A)   Jiang, Jian  (A)   Venkatramesh, Mylavarapu  (B)   Gruys, Kenneth J (A)   Valentin, Henry E (A)
Affiliations:	(A): Monsanto Company (B): Renessen LLC

Tocopherols are synthesized by certain photosynthetic bacteria and plants and are micronutrients with antioxidant properties that play key roles in animal and human nutrition. Biosynthesis of tocopherol can be enhanced through increasing the supply of the tocopherol precursors, homogentisic acid (HGA) and phytyldiphosphate (PPP). Increased homogentisic acid production was detected in Synechocystis through a dark coloration of culture supernatant when the p-hydroxyphenylpyruvate dioxygenase (HPPD) and bifunctional prephenate dehydrogenase (tyrA) were expressed. In transgenic Arabidopsis, seed-specific expression of the same two genes produced dark colored seeds. Alteration of HGA-levels in such seeds was confirmed by LC-MS, and oxidative byproducts of HGA are known to produce a dark coloration. Coordinated expression of HPPD, tyrA, homogentisate phytyltransferase (VTE2), and geranylgeranyldiphosphate reductase (GGR) in Synechocystis led to a total tocopherol increase of 16.5-fold compared to control cultures. Similarly, when HPPD, tyrA, and VTE2 were expressed in transgenic Arabidopsis, soybean and Canola seeds, tocopherol levels increased up to 5-, 4.12-, and 3.65-folds, respectively, with the majority of tocopherols being accumulated as tocotrienols. Tocotrienols represent another class of tocopherol compounds with their own health benefits. This work and previous studies now provide the tools for precise tailoring of oil seeds for tocopherol content and composition to enhance oil stability and nutritional value.