Gene expression and functional analyses of odorant receptors in small hive beetles (Aethina tumida)

Authors: LIU, YUANZHEN - University Of Bern; BEAUREPAIRE, ALEXIS - (NCE, CECR)networks Of Centres Of Exellence Of Canada, Centres Of Excellence For Commercilization A; Rogers, Curtis; Lopez, Dawn; Evans, Jay; STRAUB, LARS - University Of Bern; NEUMANN, PETER - University Of Bern; Cook, Steven; HUANG, QIANG - Jiangxi Agricultural University

Submitted to: International Journal of Molecular Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/25/2020
Publication Date: 6/27/2020
Citation: Liu, Y., Beaurepaire, A., Rogers, C.W., Lopez, D.L., Evans, J.D., Straub, L., Neumann, P., Cook, S.C., Huang, Q. 2020. Gene expression and functional analyses of odorant receptors in small hive beetles (Aethina tumida). International Journal of Molecular Sciences. 21(13):4582. https://doi.org/10.3390/ijms21134582.
DOI: https://doi.org/10.3390/ijms21134582

Interpretive Summary: The small hive beetle (SHB) is an invasive pest and a key nuisance parasite of honey bee colonies, spoiling honey bee products and driving bees out from colonies, resulting in colony mortality. SHB are especially damaging for declining bee colonies and small colonies used in bee breeding. SHB locate bee colonies by both smell and visual cues. Here we address the means used by beetles to find honey bee colonies, by describing a broad class of proteins (olfactory receptors) used to locate bee colonies and, potentially, other beetles for mating. We were able to name these proteins, compare them to those used by other beetles, and show how some of them respond to the presence of honey bees. The results will improve the search for novel controls of this pest, from improved baits for beetle traps to attempts to repel beetles from their honey bee hosts.

Technical Abstract: The ability of insects to respond to chemical cues in the environment is primarily determined by odorant receptors (Ors). Comparative analyses of the Or gene family between species may therefore shed light on the evolution and the relative importance of olfaction across different life histories. The small hive beetle, Aethina tumida, is a parasite of social bee colonies, depends on olfactory cues to locate host colonies. However, it is unclear how the Or gene family evolved as an adaptation towards infesting bee colonies. Here, we queried Or orthologues and conducted phylogenetic analyses of the Or gene family in A. tumida and three other species (Apis mellifera, Tribolium castaneum, Nasonia vitripennis) with different ecological niches. Our results show fewer Or gene family members in A. tumida. Structural analyses of odorant co-receptor (Orco) genes further suggest that A. tumida Orco is highly conserved compared with T. castaneum. These results may reflect the adaptation of A. tumida to a specialized parasitic life style in colonies and may also foster parasite control via Orco gene silencing. We also confirmed sex-specific expression of three SHB OR's and showed differences in gene expression with respect to exposure of beetles to honey bees, a first step in establishing functional roles of distinct OR's.