Demonstration of de Novo pheromone biosynthesis in Ips duplicatus (Coleoptera: Scolytidae): inhibition of Ipsdienol and E-Myrcenol production by compactin

The biosynthesis of ipsdienol and E-myrcenol was studied in the bark beetle Ips duplicatus by using the enzyme inhibitor compactin. The inhibitor specifically blocks the action of the enzyme hydroxy-methylglutaryl-coenzyme A reductase, that operates early in terpene biosynthesis prior to the formation of mevalonate. Compactin was injected in the beetle's abdomen using a thin tapered glass needle; controls were injected with saline blank. The release of ipsdienol and E-myrcenol was reduced by 70 and 40% respectively in I. duplicatus beetles injected with compactin over a period of 17–25 h after injection. Thus, ipsdienol and E-myrcenol can be synthesized de novo and not only by the hydroxylation of exogenous myrcene, from the resin of the attacked host trees. To test the possibility that the inhibitor causes a non-specific metabolic depression of the beetles, I. typographus was subjected similarly and monitored for the hydroxylation of (−)-α-pinene, forming cis-verbenol. The production of cis-verbenol is not affected by compactin.