Graduate student University of Florida GAINESVILLE, Florida
Body of Abstract: Carotenoids, the naturally occurring pigments, are essential for human nutrition and health. Depending on their chemical properties, different carotenoids can serve as antioxidants, precursors of vitamin A, or macular pigments for visual function. Capsanthin and capsorubin are k-cyclic carotenoids, specifically known in pepper fruit. Both show excellent antioxidative ability, pharmacological activities in preclinical studies. Capsanthin-capsorubin synthase (CCS) is the enzyme responsible for the biosynthesis of capsanthin and capsorubin. CCS has been shown to have catalytic activity of lycopene beta-cyclase (LCYB) in vitro suggesting that both LCYB and CCS have catalytic function to convert lycopene into beta-carotene. Due to this bifunction, CCS is a potential candidate for altering carotenoid pathway in certain crop plants to improve the carotenoid composition and contents. Coding sequence of CCS was cloned from cDNA of ripe pepper fruit into a plant expression vector. Micro-Tom cultivar was transformed by Agrobacterium-mediated method. When CCS was introduced into tomato, the flower turned into reddish orange instead of bright yellow. Besides, tomato fruit from CCS-transgenic lines showed orange color compared to the red color of empty vector line fruit, suggesting the change of carotenoid profile. Further analyses by HPLC-Vis/UV, capsanthin was identified in both flower and fruit samples from CCS-lines, indicating its successful biosynthesis in tomato. Last but not least, beta-carotene in tomato fruit from CCS transgenic line increased by 6 to10 times compared to vector control transgenic lines, suggesting that the carotenoid pathway was altered toward the direction of accumulating more valuable carotenoids. In most tomato varieties, fruit accumulates lycopene up to 90% of total carotenoids. Effort is made by breeders and researchers to generate tomato varieties with higher contents of beta-carotene. In addition to traditional approach, the transgenic lines generated by the approach of synthetic biology are promising and will serve as an excellent example for crop improvement.