Microbial Mediators of Pine Defense Resistance: Stage-Specific Gut Symbionts Enable Acantholyda posticalis to Overcome Terpenoid Barriers.

Acantholyda posticalis (Matsumura) is a globally significant forest pest that inflicts substantial economic losses through its feeding activity on Pinus species. As an oligophagous insect, A. posticalis relies critically on its gut microbiota to overcome the defensive secondary metabolites of pine needles, particularly α- and β-pinene terpenoids. This study investigated the dynamic compositional changes of gut bacterial communities across different developmental stages of A. posticalis and characterized their functional roles in host adaptation. Through traditional culturing methods, two pinene-degrading bacterial strains-Klebsiella variicola and Enterobacter hormaechei-were isolated from the larval gut. In vitro assays demonstrated their significant capacity to degrade the two pinenes. High-throughput 16S rRNA sequencing revealed stage-specific bacterial enrichment patterns. Functional prediction suggested these microbial communities participate in critical metabolic processes, including phosphotransferase systems, GST activity, and detoxification pathways. This work advances understanding of insect-microbe symbiosis in oligophagous systems and proposes novel strategies for ecologically sustainable A. posticalis control through manipulation of its gut microbiota.