MicroRNA ame-let-7 targets Amdop2 to increase sucrose sensitivity in honey bees (Apis mellifera).

Background: As an important catecholamine neurotransmitter in invertebrates and vertebrates, dopamine plays multiple roles in the life of the honey bee. Dopamine receptors (DA), which specifically bind to dopamine to activate downstream cascades, have been reported to be involved in honey bee reproduction, division of labour, as well as learning and motor behaviour. However, how dopamine receptors regulate honey bee behavior remains uninvestigated.

Results: The expression level of Amdop2 in the brain increased with the age of worker bees, which was just the opposite trend of ame-let-7. Inhibition of ame-let-7 through feeding an inhibitor upregulated Amdop2 expression; conversely, overexpression of ame-let-7 through a mimic downregulated Amdop2. Moreover, knockdown of Amdop2 in forager brain led to significantly higher sucrose responsiveness, which is similar to the phenotype of overexpression of ame-let-7. Finally, we confirmed that ame-let-7 directly targets Amdop2 in vitro by a luciferase reporter assay.

Conclusions: ame-let-7 is involved in the dopamine receptor signaling pathway to modulate the sucrose sensitivity in honey bees. Specifically, it down-regulates Amdop2, which then induces higher responses to sucrose. These results further unraveled the diverse mechanisms of the dopamine pathway in the regulation of insect behavior.