Gut bacteria prime and reinforce mature leaf oviposition preference in beetles via plant mediated feedback

The gut microbiota can profoundly influence host behavior, yet underlying mechanisms for microbiota-driven behavioral adaptation remain elusive. We previously observed that female Plagiodera versicolora leaf beetles preferentially oviposit on mature leaves despite feeding on new leaves. Here, we demonstrate that this oviposition preference is gut microbiota-dependent, as it is abolished by microbiota depletion and restored by microbiota transplantation. Gut Pseudomonas putida emerges as the key driver, with its abundance positively correlating with mature-leaf preference. Further investigation reveals that beetle feeding induces elevated indole-3-acetic acid (IAA) levels, promoting bacterial translocation from feeding sites to new leaves. This colonization facilitates bacterial dissemination while reducing F1 fitness during larval feeding. Comparative transcriptomics implicates the takeout gene (TO1) in regulating oviposition preference, and TO1 knockdown abolishes this behavior. Moreover, P. putida supplementation restores TO1 expression and mature-leaf preference in germ-free females. These findings reveal an insect–microbe–plant feedback loop driving microbiota-associated behavioral adaptation. Gut bacteria influence where willow leaf beetles lay their eggs. A specific bacterium transmits between insects via damaged host plants, reinforcing egg-laying behaviors linked to offspring performance.