RNAi targeting the gene for 1,8-cineole synthase induces recomposition of leaf essential oil in lavandin (Lavandula × intermedia Emeric)

Recomposition of volatile compounds is an effective way to alter the fragrance of an essential oil. Using RNA interference (RNAi), we attempted to reduce the production of 1,8-cineole, a major monoterpene in essential oils, to alter the composition of the essential oil in lavandin. We obtained 12 transgenic regenerants via inoculation with Agrobacterium tumefaciens, including an RNAi inducing vector targeting five regions of the gene for 1,8-cineole synthase (CINS). Of these, two regenerants, targeting a coding region about 250 nt upstream with 5′-UTR and a coding region about 300 nt downstream of CINS mRNA (CINS I and V), respectively, showed a significant decrease of 1,8-cineole production in leaf essential oil, although the overall composition was barely altered because the production of other compounds decreased concurrently. By contrast, in two other regenerants, targeting a coding region about 1000 nt in the middle and a coding region about 300 nt downstream of CINS mRNA (CINS IV and V), respectively, 1,8-cineole production could be barely observed, without any decrease in production of other compounds. Expression of CINS in these transgenic regenerants was extremely suppressed to 0.02 and 0.08 of that of a nontransgenic regenerant control. The composition of leaf essential oil in the transgenic regenerants was changed by the RNAi. Specifically, the major compounds changed from 1,8-cineole, camphor, and borneol, to linalool, camphor, and borneol. Consequently, the fragrance of essential oils of these plants was perceived as more citrusy than the fragrance of the nontransgenic regenerant. These results suggest that the knockdown strategy was a useful tool for altering the fragrance in lavandin.