Engineering ketocarotenoid biosynthesis in potato tubers

Consumption of astaxanthin is increasingly associated with a range of health benefits. Attempts to engineer ketocarotenoid biosynthesis in plants have been successful although there are no reports of nutritionally significant levels of astaxanthin in plant storage organs. Thus, in this study, ketocarotenoid biosynthesis was engineered in potato tubers. Both Solanum tuberosum and Solanum phureja transgenic lines were produced that expressed an algal bkt1 gene, encoding a beta-ketolase, and accumulated ketocarotenoids. Two major ketocarotenoids were detected, ketolutein and astaxanthin. The level of unesterified astaxanthin reached ca. 14 microg g(-1) DW in some bkt1 expressing lines of S. phureja but was much lower in the S. tuberosum background. Co-transformation of S. tuberosum with crtB, encoding phytoene synthase, and the bkt1 gene was achieved in order to determine whether this would enhance the levels of S. tuberosum ketocarotenoid.