Cloning and Expression of Putative Rac/Rop GTPase Genes, Am-rac1 and Am-rac2, Involved in Methyl Jasmonate-Induced Transcriptional Activation of Farnesyl Diphosphate Synthase in Cell Cultures of Aquilaria microcarpa

A homology-based cloning strategy yielded two cDNA clones presumably encoding Rac/Rop GTPases, Am-rac1 and Am-rac2, from callus cultures of Aquilaria microcarpa. Transcriptional levels of Am-rac1, measured using reverse transcription polymerase chain reaction, remained steady, while those of Am-rac2 increased dramatically following treatment of cultured cells with either a yeast extract or methyl jasmonate. These results suggested that Am-rac1 was a constitutively expressed homologue, while Am-rac2 was induced in A. microcarpa cells. Moreover, a farnesyl diphosphate synthase gene of A. microcarpa, Am-FaPS1, was transcriptionally activated in A. microcarpa cells grown in the presence of methyl jasmonate; however, expression levels were markedly lowered in the presence of various signal transduction-related inhibitors involved in Ca²⁺-, Rap/Rop GTPase-, or ubiquitin-dependent signaling processes. Whereas, expression of Am-FaPS1 was markedly increased, even in the absence of methyl jasmonate in A. microcarpa cells over-expressing Am-rac2. These findings suggested that Rac/Rop GTPase proteins played important roles in jasmonate-induced enhancement of terpenoid metabolism in A. microcarpa.