Immune gene expression in developing honey bees (Apis mellifera L.) simultaneously exposed to imidacloprid and Varroa (Varroa destructor Anderson and Trueman) in laboratory conditions

Authors: TESCOVNIK, TANJA - University Of Ljubljana; ZORC, MINJA - University Of Ljubljana; GREGORC, ALES - Mississippi State University; Rinehart, Timothy - Tim; Adamczyk, John; NARAT, MOJCA - University Of Ljubljana

Submitted to: Journal of Apicultural Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2019
Publication Date: 7/4/2019
Citation: Tescovnik, T., Zorc, M., Gregorc, A., Rinehart, T.A., Adamczyk Jr, J.J., Narat, M. 2019. Immune gene expression in developing honey bees (Apis mellifera L.) simultaneously exposed to imidacloprid and Varroa (Varroa destructor Anderson and Trueman) in laboratory conditions . Journal of Apicultural Research. 730-739. doi.org/10.1080/00218839.2019.1634463.
DOI: https://doi.org/10.1080/00218839.2019.1634463

Interpretive Summary: The impact of widespread pesticide use in agriculture has been a major concern to the beekeeping industry. Accumulating evidence suggests that pesticides have a negative impact on honey bees. Additionally, honey bees exposed to different stressors, such as parasites and the pathogens they vector, may further affect their health. The aim of this study was to investigate the combined or sole effect of two stressors on developing honey bees under laboratory conditions where larvae were treated with realistic field doses of the insecticide, imidacloprid, and later infested with the parasitic mite, Varroa destructor (varroa). Here we present a gene expression profile of 15 immune related genes in different honey bee development stages. Our results show that pesticide consumed in the larval stage led to a decrease in the immune response in early development stages while in later stages, an increase in honey bee immune response was observed. The gene expression pattern of varroa infested honey bees changed during development, whereby a number of significantly elevated genes increased during development. The effect of both stressors had significant effect on antimicrobial peptides and genes involved in defense in different developmental stages. All tested honey bees exposed to varroa had significantly elevated of a virus that causes deformed wings (DMV virus). In the imidacloprid plus varroa group we observed high levels of DWV virus, but only significance was in newly emerged bees.

Technical Abstract: The impact of widespread pesticide use in agriculture has been a major concern to the beekeeping industry. Accumulating evidence suggests that pesticides have a negative impact on honey bees. Additionally, honey bees exposed to different stressors, such as parasites and the pathogens they vector, may further affect their health. The aim of this study was to investigate the combined or sole effect of two stressors on developing honey bees under laboratory conditions where larvae were per os treated with realistic field doses of imidacloprid and later infested with Varroa destructor (varroa). Here we present a gene expression profile of 15 immune related genes in different honey bee development stages (white-eyed, brown-eyed pupae, and emerged honey bees). Our results show that pesticide consumed in larval stage lead to decrease in the immune response of bees in early development stages (white- and brown-eyed pupae) while in later stages, an increase in honey bee immune response was observed. The gene expression pattern of varroa infested honey bees changed during development, whereby the number of significantly elevated genes increased from white-eyed pupae to newly emerged honey bees. The effect of both stressors have significant effect on antimicrobial peptides and genes involved in defense (apidaecin, hymenoptaecin, defensin-1, lysozyme-2, and PPO) of honey bees in different developmental stages. All tested hone