Characteristic alatoid ‘cineole cassette’ monoterpene synthase present in Nicotiana noctiflora

Abstract

Nicotiana species of the section Alatae emit a characteristic floral scent comprising the' cineole cassette' monoterpenes 1,8-cineole, limonene, myrcene, β-pinene, α-pinene, sabinene and α-terpineol. All previously isolated 'cineole cassette'-monoterpene synthase genes are multi product enzymes that synthesize the seven compounds of the 'cineole cassette'. Interestingly, so far this 'alatoid' trait was only shared with the eponymous species Nicotiana suaveolens of the sister section Suaveolentes. To determine the origin of the 'cineole cassette' monoterpene phenotype other potential parent species of section Noctiflorae or Petunoides as well as of the distantly related section Trigonophyllae were analysed. A monoterpene synthase producing the set of 'cineole cassette' compounds was isolated from N. noctiflorae. N. obtusifolia emitted solely 1,8-cineole and no monoterpenes were found in floral scents of N. petunoides and N. palmeri. Interestingly, the phylogenetic analysis clustered the new gene of N. noctiflora closely to the terpineol synthase genes of e.g. N. alata rather than to cineole synthase genes of e.g. N. forgetiana.