Gene expression in honey bee (Apis mellifera) larvae exposed to pesticides and Varroa mites (Varroa destructor)

Honey Bee Research and Extension Laboratory, Department of Entomology and Nematology, University of Florida, Natural Area Drive, Gainesville, FL 32611, USA.
Journal of insect physiology (Impact Factor: 2.47). 04/2012; 58(8):1042-9. DOI: 10.1016/j.jinsphys.2012.03.015
Source: PubMed

ABSTRACT Honey bee (Apis mellifera) larvae reared in vitro were exposed to one of nine pesticides and/or were challenged with the parasitic mite, Varroa destructor. Total RNA was extracted from individual larvae and first strand cDNAs were generated. Gene-expression changes in larvae were measured using quantitative PCR (qPCR) targeting transcripts for pathogens and genes involved in physiological processes, bee health, immunity, and/or xenobiotic detoxification. Transcript levels for Peptidoglycan Recognition Protein (PGRPSC), a pathogen recognition gene, increased in larvae exposed to Varroa mites (P<0.001) and were not changed in pesticide treated larvae. As expected, Varroa-parasitized brood had higher transcripts of Deformed Wing Virus than did control larvae (P<0.001). Varroa parasitism, arguably coupled with virus infection, resulted in significantly higher transcript abundances for the antimicrobial peptides abaecin, hymenoptaecin, and defensin1. Transcript levels for Prophenoloxidase-activating enzyme (PPOact), an immune end product, were elevated in larvae treated with myclobutanil and chlorothalonil (both are fungicides) (P<0.001). Transcript levels for Hexameric storage protein (Hsp70) were significantly upregulated in imidacloprid, fluvalinate, coumaphos, myclobutanil, and amitraz treated larvae. Definitive impacts of pesticides and Varroa parasitism on honey bee larval gene expression were demonstrated. Interactions between larval treatments and gene expression for the targeted genes are discussed.

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Available from: Aleš Gregorc, Sep 26, 2015
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    • "LeConte et al. (2011) found that the levels of CYP4G11 expression in the brains of A. mellifera varied according to hygienic behaviour, suggesting that the enzyme 'might catalyse a reaction in some metabolic pathways that could be involved in hygienic behavior'. Additionally, honeybee larvae in colonies infested with varroa mites significantly decreased CYP4G11 expression by threefold (Gregorc et al., 2012) and adult honeybees in colonies diagnosed with Colony Collapse Disorder were characterized by significantly down-regulated CYP4G11 expression (Johnson et al., 2009). In the closely related congener Apis cerana cerana, the eastern honeybee, AccCYP4G11 was maximally expressed in epidermal tissue within an individual, and, across life stages, in 14-day-old adults (Shi et al., 2014). "
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    ABSTRACT: In insects, cytochrome P450 monooxygenases (P450s) contribute to phytochemical and pheromone clearance in chemoreception and xenobiotic detoxification in food processing. In eusocial species, P450 expression varies with anatomy and age-related behaviour. Adult honeybees (Apis mellifera) possess appendages differentially equipped for chemoreception; antennae and prothoracic and mesothoracic legs assess food and pheromone signals whereas metathoracic legs transport pollen over long distances. Newly eclosed bees and nurses remain in the hive and neither gather nor process food, whereas foragers collect pollen and nectar, thereby encountering phytochemicals. To understand the functions of cytochrome P450, family 4, subfamily G, polypeptide 11 (CYP4G11) in the honeybee genome, we compared its expression relative to worker age and task to expression of cytochrome P450, family 9, subfamily Q, polypeptides (CYP9Qs) known to metabolize xenobiotics. That CYP4G11 is highly expressed in forager antennae and legs, with highest expression in prothoracic and mesothoracic legs, is consistent with chemosensory perception, whereas weak expression of CYP4G11 in nurses suggests that it may process primarily exogenous rather than endogenous chemical signals. By contrast, and consistent with xenobiotic detoxification, the three CYP9Q transcripts were almost undetectable in newly eclosed workers and highest in foragers, with maximal expression in the metathoracic legs that closely contact pollen phytochemicals. These CYP4G11 expression patterns suggest a role in processing environmental signals, particularly those associated with food. © 2015 The Royal Entomological Society.
    Insect Molecular Biology 07/2015; 24(5). DOI:10.1111/imb.12183 · 2.59 Impact Factor
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    • "However, in a recent study (Boncristiani et al., 2012) examining five different pesticides (including coumaphos and two other pesticides commonly applied to manage Varroa mites, thymol and formic acid) the only P450 to be upregulated was CYP6A514 by thymol; however, several other detoxification, immune, and developmental genes were either up or downregulated by thymol, coumaphos, and formic acid. Another study examining the effects of pesticides (including coumaphos and fluvalinate) on larval development (Gregorc et al., 2012), found no changes in P450 gene expression, but expression of several genes involved in immune function and behavioral maturation were significantly impacted. Finally, exposure to neonicotinoids results in reduced activity of the NF-jB immune signaling pathway and increased titers of Deformed Wing Virus (Nazzi et al., 2012), suggesting that honey bees compromised by pesticide exposure may be more susceptible to pathogen infection. "
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    ABSTRACT: Populations of pollinators are in decline worldwide. These declines are best documented in honey bees and are due to a combination of stressors. In particular, pesticides have been linked to decreased longevity and performance in honey bees; however, the molecular and physiological pathways mediating sensitivity and resistance to pesticides are not well characterized.We explored the impact of coumaphos and fluvalinate, the two most abundant and frequently detected pesticides in the hive, on genome-wide gene expression patterns of honey bee workers. We found significant changes in 1118 transcripts, including genes involved in detoxification, behavioral maturation, immunity, and nutrition. Since behavioral maturation is regulated by juvenile hormone III (JH), we examined effects of these miticides on hormone titers; while JH titers were unaffected, titers of methyl farnesoate (MF), the precursor to JH, were decreased. We further explored the association between nutrition- and pesticide-regulated gene expression patterns and demonstrated that bees fed a pollen-based diet exhibit reduced sensitivity to a third pesticide, chlorpyrifos. Finally, we demonstrated that expression levels of several of the putative pesticide detoxification genes identified in our study and previous studies are also upregulated in response to pollen feeding, suggesting that these pesticides and components in pollen modulate similar molecular response pathways.Our results demonstrate that pesticide exposure can substantially impact expression of genes involved in several core physiological pathways in honey bee workers. Additionally, there is substantial overlap in responses to pesticides and pollen-containing diets at the transcriptional level, and subsequent analyses demonstrated that pollen-based diets reduce workers' pesticide sensitivity. Thus, providing honey bees and other pollinators with high quality nutrition may improve resistance to pesticides.
    Journal of Insect Physiology 12/2014; 71:177-90. DOI:10.1016/j.jinsphys.2014.10.002 · 2.47 Impact Factor
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    • "Similar to all other insects, the honeybees lack a classically adaptive immune system as in the case of mammalian [6]. To survive, they have evolved cellular and humoral immune responses to cope with microbial infections. A. mellifera may develop cellular and humoral immune responses to various pathogens such as bacteria [13], [14], viruses [15], microsporidian [16]–[18] and Varroa mites [19], [20]. Usually, the viral infection causes cell apoptosis, tissue damage and even functional disorder of the whole organism and all these changes can be further reflected in proteome alteration [21]. "
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    ABSTRACT: Chinese honeybee Apis cerana (Ac) is one of the major Asian honeybee species for local apiculture. However, Ac is frequently damaged by Chinese sacbrood virus (CSBV), whereas Apis mellifera (Am) is usually resistant to it. Heterospecific royal jelly (RJ) breeding in two honeybee species may result in morphological and genetic modification. Nevertheless, knowledge on the resistant mechanism of Am to this deadly disease is still unknown. In the present study, heterospecific RJ breeding was conducted to determine the effects of food change on the larval mortality after CSBV infection at early larval stage. 2-DE and MALDI-TOF/TOF MS proteomic technology was employed to unravel the molecular event of the bees under heterospecific RJ breeding and CSBV challenge. The change of Ac larval food from RJC to RJM could enhance the bee resistance to CSBV. The mortality rate of Ac larvae after CSBV infection was much higher when the larvae were fed with RJC compared with the larvae fed with RJM. There were 101 proteins with altered expressions after heterospecific RJ breeding and viral infection. In Ac larvae, 6 differential expression proteins were identified from heterospecific RJ breeding only, 21 differential expression proteins from CSBV challenge only and 7 differential expression proteins from heterospecific RJ breeding plus CSBV challenge. In Am larvae, 17 differential expression proteins were identified from heterospecific RJ breeding only, 26 differential expression proteins from CSBV challenge only and 24 differential expression proteins from heterospecific RJ breeding plus CSBV challenge. The RJM may protect Ac larvae from CSBV infection, probably by activating the genes in energy metabolism pathways, antioxidation and ubiquitin-proteasome system. The present results, for the first time, comprehensively descript the molecular events of the viral infection of Ac and Am after heterospecific RJ breeding and are potentially useful for establishing CSBV resistant populations of Ac for apiculture.
    PLoS ONE 08/2014; 9(8):e102663. DOI:10.1371/journal.pone.0102663 · 3.23 Impact Factor
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