Transcriptional activation of sesquiterpene biosynthetic enzyme δ-guaiene synthase gene in cell cultures of Aquilaria microcarpa overexpressing cam1 and rac2 encoding calmodulin and Rac GTPase

Expression level of a sesquiterpene biosynthetic enzyme gene, δ-GS, encoding δ-guaiene synthase of Aquilaria microcarpa markedly elevated when cultured cells of the plant were treated with methyl jasmonate. The methyl jasmonate-induced expression of δ-GS was, however, appreciably reduced in a dose-dependent manner in the presence of N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and NSC23766, the specific inhibitors for calmodulin- and Rac GTPase-dependent cellular processes. Transformation of A. microcarpa cell culture by cam1 and rac2, calmodulin and Rac GTPase genes isolated from the plant, triggered the transcriptional activation of δ-GS even in the absence of methyl jasmonate. In contrast, A. microcarpa cultures overexpressing mutated rac2 of which translate is lacking in binding ability toward GTP did not show the significant expression of δ-GS gene. These results suggest that calmodulin and Rac GTPase proteins function as the important mediators in jasmonate-induced activation of sesquiterpene biosynthesis in A. microcarpa.