Isolation and characterization of terpene synthases potentially involved in flavor development of ripening olive (Olea europaea) fruits

The flavor and taste of fruits are often determined by terpenes. We identified three cDNAs encoding putative terpene synthases from olive fruits of cv. Frantoio and Grignano. Heterologous expression in a bacterial system demonstrated that one of the terpene synthases, OeGES1, was an active monoterpene synthase that converted geranyl diphosphate to the monoterpene alcohol geraniol. The transcript accumulation pattern of this gene showed a peak during fruit ripening in both genotypes, indicating that the enzyme may be involved in the production of monoterpene flavor compounds in olive fruit. Although the putative terpene synthases OeTPS2 and OeTPS3 clustered with alpha-farnesene synthases and angiosperm monoterpene synthases, no detectable in vitro activity was found after expression in a bacterial system. Nevertheless, their transcripts sharply accumulated during fruit ripening starting from veraison.