Browsing by Author "Evans, Jay D."

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Colony-Level Effects of Amygdalin on Honeybees and Their Microbes
(Mdpi, 2020) Tauber, James P.; Tozkar, Cansu O.; Schwarz, Ryan S.; Lopez, Dawn; Irwin, Rebecca E.; Adler, Lynn S.; Evans, Jay D.
Simple Summary Nectar compounds have the potential to affect microbial communities and pollinator immunity. Here, we investigated how the almond compound, amygdalin, influences the microbial community of the western honeybee. Using RNA sequencing technology to count microbial reads and bee gene transcripts, we show relatively no large change of bacterial counts, fungal counts or bee transcripts due to amygdalin treatment at the colony level. Larger fluctuations, perhaps due to amygdalin, were observed for pathogenic viruses and the pathogen Lotmaria passim; however, these changes could have been seasonal. Overall, amygdalin consumption at field-relevant, colony-levels may not have a large impact on bee symbionts or immune gene expression. Amygdalin, a cyanogenic glycoside, is found in the nectar and pollen of almond trees, as well as in a variety of other crops, such as cherries, nectarines, apples and others. It is inevitable that western honeybees (Apis mellifera) consistently consume amygdalin during almond pollination season because almond crops are almost exclusively pollinated by honeybees. This study tests the effects of a field-relevant concentration of amygdalin on honeybee microbes and the activities of key honeybee genes. We executed a two-month field trial providing sucrose solutions with or without amygdalin ad libitum to free-flying honeybee colonies. We collected adult worker bees at four time points and used RNA sequencing technology and our HoloBee database to assess global changes in microbes and honeybee transcripts. Our hypothesis was that amygdalin will negatively affect bee microbes and possibly immune gene regulation. Using a log(2) fold-change cutoff at two and intraday comparisons, we show no large change of bacterial counts, fungal counts or key bee immune gene transcripts, due to amygdalin treatment in relation to the control. However, relatively large titer decreases in the amygdalin treatment relative to the control were found for several viruses. Chronic bee paralysis virus levels had a sharp decrease (-14.4) with titers then remaining less than the control, Black queen cell virus titers were lower at three time points (<-2) and Deformed wing virus titers were lower at two time points (<-6) in amygdalin-fed compared to sucrose-fed colonies. Titers of Lotmaria passim were lower in the treatment group at three of the four dates (<-4). In contrast, Sacbrood virus had two dates with relative increases in its titers (>2). Overall, viral titers appeared to fluctuate more so than bacteria, as observed by highly inconstant patterns between treatment and control and throughout the season. Our results suggest that amygdalin consumption may reduce several honeybee viruses without affecting other microbes or colony-level expression of immune genes.
Immune Gene Expression and Locomotor Activity in Response To Vairimorpha Ceranae Infection Across Five Honey Bee Subspecies
(Mdpi, 2025) Tozkar, Cansu Ozge; Evans, Jay D.
This study evaluated immune gene expression and locomotor behavior across five Apis mellifera subspecies (Carniolan, Caucasian, Syrian, Mu & gbreve;la ecotype, and Y & imath;& gbreve;& imath;lca ecotype) following controlled Vairimorpha ceranae infection. Six days post-infection, Caucasian, Carniolan, and Y & imath;& gbreve;& imath;lca bees exhibited a significant upregulation of antimicrobial peptide (AMP) transcripts-hymenoptaecin, abaecin, defensin, and apidaecin-indicating a robust humoral response. Conversely, Syrian and Mu & gbreve;la bees showed weaker AMP expression and higher V. ceranae mRNA levels, indicating lower immunity and higher susceptibility. Positive correlations among AMP transcripts, especially in Caucasian, Carniolan, and Y & imath;& gbreve;& imath;lca bees, suggested a coordinated response. Eater gene expression, critical for cellular immunity, decreased in infected Caucasian and Y & imath;& gbreve;& imath;lca bees, coinciding with AMP upregulation. Vitellogenin expression, linked to immunity and longevity, increased in Carniolan and Syrian bees, correlating with higher early locomotor activity. Locomotor analysis revealed subspecies-specific behavioral responses. Syrian bees maintained the highest activity despite elevated V. ceranae mRNA and minimal AMP expression, suggesting unique resilience possibly mediated by vitellogenin. Mu & gbreve;la bees, despite high pathogen loads, exhibited decreased activity. Caucasian bees showed strong immune responses but reduced activity post-infection, reflecting potential physiological trade-offs. Overall, these findings underscore the role of genetic variability in shaping honey bee immune and behavioral responses to Vairimorpha and support subspecies-targeted breeding and disease management strategies to enhance resilience.
Nectar and Pollen Phytochemicals Stimulate Honey Bee (Hymenoptera: Apidae) Immunity To Viral Infection
(Oxford Univ Press inc, 2017) Palmer-Young, Evan C.; Tozkar, Cansu O.; Schwarz, Ryan S.; Chen, Yanping; Irwin, Rebecca E.; Adler, Lynn S.; Evans, Jay D.
Parasites and pathogens are implicated in honey bee colony losses, and honey bees may also spread infection to wild pollinators. Bees consume nectar and pollen, which contain phytochemicals that can positively or negatively affect pollinator health. Certain phytochemicals can reduce parasite loads in humans and other animals. Understanding how phytochemicals affect honey bee infection and survival could help identify optimal forage sources and phytochemical treatments to ameliorate disease. We fed honey bees seven dietary phytochemicals to evaluate whether phytochemical consumption would treat preexisting infection in mature bees, or mitigate infection in young bees either inside or outside of their colonies. Phytochemicals were generally well-tolerated at levels documented in nectar, honey, and pollen, although clove oil and thymol increased mortality at high doses. Six of seven tested phytochemicals significantly increased antimicrobial peptide expression by 12.9 to 61-fold in older bees after 7 d consumption. Short-term (< 24 h) phytochemical consumption reduced levels of Deformed wing virus (DWV) up to 500-fold in young bees released into field colonies. However, with the exception of high-dose clove oil, our phytochemical treatments did not alter infection with Lotmaria passim or Nosema ceranae. Phytochemicals also lacked antiviral effects for pollen-deprived bees reared outside the colony. Our results suggest that phytochemicals have potential therapeutic value for honey bees infected with DWV. Short-term phytochemical consumption may be sufficient to confer benefits against infection. Phytochemical concentrations that reduced disease were comparable with naturally occurring floral concentrations, suggesting that flowers could serve as seasonally varied, serially consumed pollinator medicines.