Gut bacteria induce oviposition preference through ovipositor recognition in fruit fly.

Gut bacteria play important roles in insect life cycle, and various routes can be used by insects to effectively transmit their gut bacteria. However, it is unclear if the gut bacteria can spread by actively attracting their insect hosts, and the recognition mechanisms of host insects are poorly understood. Here, we explore chemical interactions between Bactrocera dorsalis and its gut bacterium Citrobacter sp. (CF-BD). We found that CF-BD could affect the development of host ovaries and could be vertically transmitted via host oviposition. CF-BD could attract B. dorsalis to lay eggs by producing 3-hexenyl acetate (3-HA) in fruits that were hosts of B. dorsalis. Furthermore, we found that B. dorsalis could directly recognize CF-BD in fruits with their ovipositors in which olfactory genes were expressed to bind 3-HA. This work reports an important mechanism concerning the active spread of gut bacteria in their host insects.