Antennally mediated negative feedback regulation of pheromone production in the pine engraver beetle, Ips pini

Abstract

Bark beetles use monoterpenoid aggregation pheromones to coordinate host colonization and mating. These chemical signals are produced de novo in midgut cells via the mevalonate pathway, and pheromone production may be regulated by a negative feedback system mediated through the antennae. In this study, we explored the effect of antennectomy on pheromone production and transcript levels of key mevalonate pathway genes in juvenile hormone III-treated male pine engraver beetles, Ips pini (Say). Antennectomized males produced significantly greater amounts of pheromone than podectomized males and those with intact antennae. Likewise, mRNA levels of three mevalonate pathway genes important in pheromone biosynthesis were measured by quantitative real-time PCR and found to be induced to a greater extent with antennectomy, suggesting a transcriptional regulation of pheromone production.

Pheromone production in bark beetles

“…Similarly, teneral male D. jeffreyi HMGR mRNA levels are not induced by JH III to the same extent as those in fully mature insects (Barkawi, 2002), suggesting developmental regulation. An antennally-mediated negative-feedback regulation in I. pini suggests possible neural influences (Ginzel et al, 2007) similar to that observed in L. decemliniata (Dickens et al, 2002). Finally, mevalonate pathway genes show a pulse of mRNA induction in fed male I. pini, whereas unfed, JH III-treated males show a steady increase in mRNA levels over time (Keeling et al, 2004.…”

“…Antennae also play a role in regulation in I. pini (Ginzel et al, 2007). Male beetles without antenna had higher levels of pheromone, a phenomena first demonstrated in the Colorado potato beetle (Dickens et al, 2002).…”

Cross-scale Drivers of Natural Disturbances Prone to Anthropogenic Amplification: The Dynamics of Bark Beetle Eruptions

“…This strategy of mass attack necessitates crowding, which reduces the resources available to each colonizer. Beetles minimize overcrowding by oxidizing aggregation pheromones into antiaggregants, both through their own and their microbial symbionts' biosynthetic pathways (Brand et al 1976) and through antennally mediated negative feedback to pheromone biosynthesis in the gut (Ginzel et al 2007). Once a tree's resistance is exhausted, the entered beetles cease production of attractive pheromones and begin production of repellant pheromones, thus limiting further arrivals to the host (Wood 1982).…”

Isolation, endocrine regulation and transcript distribution of a putative primary JH-responsive gene from the pine engraver, Ips pini (Coleoptera: Scolytidae)

“…It is thus possible that Ipi10G08 functions in JH III signaling. Given the evident complexity of regulating pheromone biosynthesis in I. pini (Ginzel et al, 2007), it is not clear if its role is direct, or as a modulator of other JH signaling components. In this respect it is interesting to note the putative kinase/phosphatase activities associated with the conserved domains in Ipi10G08-like proteins, and that phosphorylation of nuclear proteins and/or transcription factors can affect their activities at JHREs (Zhou et al, 2002;Kethidi et al, 2006).…”