Gut-Associated Bacteria of Dendroctonus valens and their Involvement in Verbenone Production

Abstract

Bark beetles are the most important mortality agent in coniferous forests, and pheromones play important roles in their management. Dendroctonus valens LeConte was introduced from North America to China and has killed millions of healthy pines there. Trapping with semiochemicals and pheromones was deployed in D. valens management in the last decade, but little is known about the ability of gut bacteria to produce the pheromone. In this study, we analyzed the volatiles in D. valens guts and frass after antibiotic treatment versus control. Then, we isolated and identified the bacteria in D. valens guts and frass, examined verbenone (a multifunctional pheromone of D. valens) production by 16 gut bacterial isolates from the precursor cis-verbenol at three concentrations, and further compared the cytotoxicities between the cis-verbenol and verbenone to the bacterial isolates. cis-Verbenol was not detected in the frass in the control group, but it was in the antibiotic treatment. The amount of verbenone was significantly suppressed in D. valens guts after antibiotic treatment versus control. Thirteen out of 16 gut bacterial isolates were capable of cis-verbenol to verbenone conversion, and cis-verbenol had stronger cytotoxicities than verbenone to all tested gut bacterial isolates. The bacterial species capable of verbenone production largely exists in D. valens guts and frass, suggesting that gut-associated bacteria may help the bark beetle produce the pheromone verbenone in guts and frass. The bacteria may benefit from the conversion due to the reduced cytotoxicity from the precursor to the beetle pheromone.

Expression, purification and characterization of an endoglucanase from Serratia proteamaculans CDBB-1961, isolated from the gut of Dendroctonus adjunctus (Coleoptera: Scolytinae)

“…Serratia spp. have been recurrently isolated from the gut of the Dendroctonus species (Morales-Jiménez et al 2009; Hu et al 2014; Vasanthakumar et al 2006; Xu et al 2015), and their relative abundance and persistence in this habitat suggest that they are part of the microbiome core of these insects (Hernández-García, personal communication). Thus, it appears probable that the cellulolytic activity from Serratia sp.…”

Pine Defensive Monoterpene α-Pinene Influences the Feeding Behavior of Dendroctonus valens and Its Gut Bacterial Community Structure

“…Gut microbiota are ubiquitous for insect herbivores and are often critical to insect biological performance and ecological functioning, such as augmentation of nutritional availability [1,2,3], protection of insects from pathogens and parasites [4,5], facilitation of pheromone production [6,7], and detoxification of harmful toxins produced by the host plant defense system [8,9]. The gut microbiome has also been recognized as a major force in shaping insect-plant interactions [10,11,12].…”

Semiochemicals in the Natural History of Southern Pine Beetle Dendroctonus frontalis Zimmermann and Their Role in Pest Management

“…Verbenone (and verbenol) can be generated through autoxidation of host-released α-pinene coming into contact with atmospheric oxygen (Hunt et al, 1989;Moore et al, 1956). Microbes including bark beetle symbionts and incidental associates are also capable of oxidizing α-pinene to verbenol and/or verbenol to verbenone Brand et al, 1975;Hunt and Borden, 1990;Xu et al, 2015). A fungus carried in the mycangium of female D. frontalis (Ceratocystiopsis ranaculosus J.R. Bridges and T.J. Perry) was shown to convert verbenol to verbenone (Brand et al, 1976).…”