Enrichment of carotenoids in flaxseed by introducing a bacterial phytoene synthase gene

Carotenoids are well-known natural pigments, typically ranging from yellow to red. Carotenoids are industrially utilized as functional materials due to their strong antioxidant properties. Phytoene synthesis is known to be a rate-determining step in the entire carotenoid biosynthetic pathway in plants. We show methods of pathway engineering for the enrichment of carotenoids in flaxseed (linseed; Linum usitatissimum L.), which is an industrially important oleaginous crop. A phytoene synthase gene (crtB) derived from a soil bacterium Pantoea ananatis (formerly called Erwinia uredovora) strain 20D3 was introduced into L. usitatissimum WARD cultivar. The resulting transgenic flax plants formed orange seeds, which contained phytoene, alpha-carotene, beta-carotene, and lutein. The total carotenoid amount in the transgenic seeds was 156 microg/g fresh weight at the maximum, corresponding to 18.6-fold increase compared with that of untransformed controls.