Researchers from Israel’s Newe Ya-ar Research Center recently published a study in Nature Biotechnology (published online here) using genetic modification to change the flavor and aroma of tomatoes. To do this, Davidovich-Rikanati et al. focused on enhancing the monoterpene content in tomatoes by expressing the lemon basil (Ocimum basilicum L. cv. Sweet Dani) geraniol synthase (GES) gene. Monoterpenes contribute many fruit and floral scents and are synthesized from geranyl diphosphate (GDP), an intermediate in carotenoid biosynthesis.
Although the carotenoid pathway is highly active in ripening tomato fruits, leading to the production of lycopene, ripe fruits contain only minute amounts of monoterpenes. GES catalyzes the conversion of GDP to geraniol, an acyclic monoterpene alcohol with an intense rose scent. Although the resulting transgenic fruits failed to develop the deep red color of the control fruits and experienced a 50% drop in the level of lycopene, the majority of untrained panelists preferred the flavor and smell of the modified tomatoes. These results show that using genetic engineering has potential for modifying the aroma and taste of other carotenoid-accumulating species of agricultural and horticultural importance. In addition, since volatile terpenoids possess antimicrobial, pesticidal and antifungal activities, such manipulations may also improve shelf life of stored fruits or reduce pesticide use.