Linalool and linalool oxide production in transgenic carnation flowers expressing the Clarkia breweri linalool synthase gene

Most modern cut-flower cultivars, including those of carnation (Dianthus caryophyllus), lack distinct fragrance. Carnation cv. Eilat flowers produce and emit various fragrance compounds, including benzoic acid derivatives and sesquiterpenes, but not monoterpenes. Based on GC-MS analysis, benzoic acid, benzyl benzoate, phenylethyl benzoate, methyl benzoate, cis-3-hexenyl benzoate and β-caryophyllene are the major fragrance compounds, representing ca. 60% of the total volatiles generated by these flowers. The level of these compounds increases dramatically during petal development. To evaluate the possibility of producing monoterpenes in carnation cv. Eilat, we generated transgenic plants expressing the linalool synthase gene from Clarkia breweri under the regulation of the CaMV 35S constitutive promoter. The product of this gene catalyzes the production of the monoterpene linalool from geranyl diphosphate. Headspace GC-MS analysis revealed that leaves and flowers of transgenic, but not control plants, emit linalool and its derivatives, cis- and trans-linalool oxide. GC-MS analysis of petal extract revealed the accumulation of trans-linalool oxide but not linalool. The emission of linalool by the transgenic flowers did not lead to detectable changes in flower scent for human olfaction.