Characterization of alpha-humulene synthases responsible for the production of sesquiterpenes induced by methyl jasmonate in Aquilaria cell culture

摘要

The resinous portions of Aquilaria and Gyrinops plants are known as 'agarwood' and have a distinctive fragrance. To examine the biosynthesis of these fragrant compounds, we previously established cell cultures of Aquilaria crassna in which the production of three sesquiterpenes (alpha-guaiene, alpha-humulene, and delta-guaiene) could be induced by methyl jasmonate (MJ), and showed that cloned delta-guaiene synthase from MJ-treated cells is involved in the synthesis of these three compounds, although only very small amounts of alpha-humulene are produced. In the present study, cDNAs encoding alpha-humulene synthases were also isolated. Three putative sesquiterpene synthase clones (AcHS1-3) isolated from the MJ-treated cells had very similar amino acid sequences and shared 52 % identity with delta-guaiene synthases. The recombinant enzymes catalyzed the formation of alpha-humulene as a major product. Expression of transcripts of the alpha-humulene synthase and delta-guaiene synthase genes in cultured cells increased after treatment with MJ. These results revealed that these alpha-humulene and delta-guaiene synthases are involved in the synthesis of three sesquiterpenes induced by MJ treatment.