Effect of a thymol application on olfactory memory and gene expression levels in the brain of the honeybee Apis mellifera
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Essential oils are used by beekeepers to control the Varroa mites that infest honeybee colonies. So, bees can be exposed to thymol formulations in the hive. The effects of the monoterpenoid thymol were explored on olfactory memory and gene expression in the brain of the honeybee. In bees previously exposed to thymol (10 or 100 ng/bee), the specificity of the response to the conditioned stimulus (CS) was lost 24 h after learning. Besides, the octopamine receptor OA1 gene Amoa1 showed a significant decrease of expression 3 h after exposure with 10 or 100 ng/bee of thymol. With the same doses, expression of Rdl gene, coding for a GABA receptor subunit, was not significantly modified but the trpl gene was upregulated 1 and 24 h after exposure to thymol. These data indicated that the genes coding for the cellular targets of thymol could be rapidly regulated after exposure to this molecule. Memory and sensory processes should be investigated in bees after chronic exposure in the hive to thymol-based preparations.
KeywordsHoneybee Olfactory conditioning Thymol TRPL RDL OA1 Real-time PCR
Proboscis extension reflex
Resistant to dieldrin
Transient receptor potential-like channel
We wish to thank Genome & Transcriptome center (Rangueil, Toulouse) for technical assistance. The work was supported by the Conseil Régional Midi-Pyrénées, the Centre National de la Recherche Scientifique, and the Centre Universitaire de Formation et de Recherche J.F. Champollion (Project 10051284). We thank Dr. P. Winterton for English language improvement.
Conflict of interest
The authors declare that there are no conflicts of interest.
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