Biology subjects

vanEngelsdorp, D.

Publications and source records attributed to vanEngelsdorp, D..

5 recordsLinked to original sources

bioRxiv2022

Kleptocytosis: A Novel Parasitic Strategy for Accelerated Reproduction via Host Protein Stealing in Varroa destructor

Varroa destructor must produce mature offspring within the inflexible nine-day window framing the pupal development of their honey bee host. Missing this deadline renders the foundress mites fitness zero, establishing evolutionary pressure to accelerate reproduction and development. Through micro-computed tomography and modeling Varroas energy budget, we found each egg grows to constitute [~]18% of the foundresss body volume in 30 hours, yet accounts for less than 10% of her energy usage. We hypothesized that this small energy investment is a successful strategy because of Varroas long-ignored ability to traffic intact host proteins. Through gel electrophoresis, concomitant immunodetection, and MS/MS, we detected several intact, bee-derived proteins in mite eggs, including metamorphic proteins (hexamerins) and egg-yolk precursors (vitellogenin and apolipophorin) which likely reduce the parasites direct reproductive investment. We then expressed recombinant Halotag labelled Apis vitellogenin to determine the route conveying exogenous proteins into the mites oocyte. We detected fluorescent vitellogenin in the lyrate organ and observed a tube-like extension of the lyrate organ connecting to the ovum, likely providing an avenue for intact host proteins. Finally, we tested the hypothesis that exogenous proteins maintain functionality in the parasite. Varroa metamorphose despite their inability to produce hexamerins, critical metamorphic proteins. Through label-free quantification of proteins in metamorphosing mites, we observed a hexamerin depletion pattern consistent with usage as a metamorphic amino acid reservoir. We describe this process as "kleptocytosis," denoting movement of stolen intact macromolecules from host to a parasite cell. Given their fixed developmental timeline, this pathway presents a promising target for novel Varroa management strategies. Significance StatementGlobal honey bee health is threatened by the parasitic mite Varroa destructor; its success due in part to its rapid reproduction and accelerated development. By combining biological modeling, micro-computed tomography, fluorescence imaging, and quantitative proteomics, we show that Varroa siphon intact, ostensibly functional host proteins conveying them directly to their oocyte. This avoids the energetically inefficient process of digesting and reconstructing ingested proteins and affords the capacity to utilize proteins that it does not produce de novo facilitating rapid reproduction and accelerated development. We call this process "kleptocytosis," and identify anatomical adaptations which apparently facilitate protein movement. This work exposes a new target in Varroas physiology, providing a promising direction for more effective management strategies.

zoology↗

bioRxiv2021

Resistance to amitraz in the parasitic honey bee mite Varroa destructor is associated with mutations in the β-adrenergic-like octopamine receptor

Varroa destructor is considered a major reason for high loss rate of Western honey bee (Apis mellifera) colonies. To prevent colony losses caused by V. destructor it is necessary to actively manage the mite population. Beekeepers, particularly commercial beekeepers, have few alternative treatments other than synthetic acaricides to control the parasite, resulting in intensive treatment regimens that led to the evolution of resistance in mite populations. To investigate the mechanism of the resistance to amitraz detected in V. destructor mites from French and U.S. apiaries, we identified and characterized octopamine and tyramine receptors (the known targets of amitraz) in this species. The comparison of sequences obtained from mites collected from different apiaries with different treatment regimens, showed that the amino acid substitutions N87S or Y215H in the Oct{beta}R were associated with treatment failures reported in French or U.S. apiaries, respectively. Based on our findings, we have developed and tested two high throughput diagnostic assays based on TaqMan(R) able to accurately detect mites carrying the mutations in this receptor. This valuable information may be of help for beekeepers when selecting the most suitable acaricide to manage V. destructor.

genetics↗

bioRxiv2020

Mutations associated with pyrethroid resistance in Varroa mites, a parasite of honey bees, are widespread across the USA

BACKGROUNDManaged honey bees are key pollinators of many crops and play an essential role in the United States food production. For more than 10 years, beekeepers in the US have been reporting high rate of colony losses. One of the drivers of this colony loss is the parasitic mite Varroa destructor. Preserving healthy honey bee colonies in the US is dependent on a successful control of this mite. The pyrethroid tau-fluvalinate (Apistan(R)) was among the first synthetic varroacide registered in the US. With over 20 years of use, population of mites resistant to Apistan(R) have emerged, and so it is unsurprising that treatment failures have been reported. Resistance in US mite populations to tau-fluvalinate is associated with point mutations at position 925 of the voltage-gated sodium channel, L925I and L925M. RESULTSHere, we have generated a distribution map of pyrethroid resistance alleles in Varroa samples collected from US apiaries in 2016 and 2017, using a high throughput allelic discrimination assay based on TaqMan(R). Our results evidence that these kdr-type mutations are widely distributed in Varroa populations across the country showing high variability among apiaries. CONCLUSIONWe highlight the relevance of monitoring the resistance in mite populations to achieve an efficient control of this pest, and the benefit of implementing this methodology in pest management programs for varroosis.

pharmacology and toxicology↗

bioRxiv2020

Social Disruption: Sublethal pesticides in pollen lead to Apis mellifera queen events and brood loss

Eusocial Apis mellifera colonies depend on queen longevity and brood viability to survive, as the queen is the sole reproductive individual and the maturing brood replenishes the shorter lived worker bees. Production of many crops rely on both pesticides and bee pollination to improve crop quantity and quality. We looked at the resiliency of queens and their brood after one month of sublethal exposure to field relevant doses of pesticides that mimic exposure during commercial pollination contracts. We exposed full size colonies to pollen contaminated with field-relevant doses of the fungicides (chlorothalonil and propicanizole), insecticides (chlorypyrifos and fenpropathrin) or both, noting a significant reduction in pollen consumption in colonies exposed to fungicides compared to control. While we found no difference in the total amount of pollen collected per colony, a higher proportion of pollen to non-pollen foragers was detected in all pesticide exposed colonies. After ceasing treatments we measured brood development, discovering a significant increase in brood loss and/or cannibalism across all pesticide exposed groups. Sublethal pesticide exposure in general was linked to reduced production of replacement workers and a change in protein acquisition (pollen vs. non-pollen foraging). Fungicide exposure also resulted in increased loss of the reproductive queen.

animal behavior and cognition↗

bioRxiv2019

Dynamic evolution in the key honey bee pathogen Deformed wing virus

The impacts of invertebrate RNA virus population dynamics on virulence and infection outcomes are poorly understood. Deformed wing virus (DWV), the main viral pathogen of honey bees, negatively impacts bee health which can lead to colony death. Despite previous reports on the reduction of DWV diversity following the arrival of the parasitic mite Varroa destructor, the key DWV vector, we found high genetic diversity of DWV in infested United States (US) honey bee colonies. Phylogenetic analysis showed that the divergent US DWV genotypes are of monophyletic origin, which were likely generated as a result of diversification after a genetic bottleneck. To investigate the population dynamics of this divergent DWV, we designed a series of novel infectious cDNA clones corresponding to co-existing DWV genotypes, thereby devising a reverse genetic system for an invertebrate RNA virus quasispecies. Equal replication rates were observed for all clone-derived DWV variants in single infections. Surprisingly, individual clones replicated to the same high levels as their mixtures and even the parental highly diverse natural DWV population, suggesting that complementation between genotypes was not required to replicate to high levels. Mixed clone-derived infections showed a lack of strong competitive exclusion, suggesting that the DWV genotypes were adapted to co-exist. Mutational and recombination events were observed across clone progeny providing new insights into the forces that drive and constrain virus diversification. Accordingly, herein we propose a new model of Varroa-induced DWV dynamics whereby an initial selective sweep is followed by virus diversification fueled by negative frequency-dependent selection for new genotypes. This selection likely reflects the ability of rare lineages to evade host defenses, specifically antiviral RNA interference (RNAi). In support of this, we show that RNAi induced against one DWV strain is less effective against an alternate strain from the same population.\n\nAuthor SummaryVirulence of Deformed wing virus (DWV), a major pathogen of honey bees, showed a sharp and significant increase following the introduction of its vector, the mite Varroa destructor. Varroa vectoring resulted in genetic changes of DWV, including reduction of DWV diversity to nearly clonal levels in the UK and Hawaii. Contrary to the previous reports, we discovered that virulent DWV populations circulating across the Varroa-infested United States included many divergent genotypes generated following a strong bottleneck event. We designed a series of the full-length infectious cDNA clones that captured the diversity of a typical virulent DWV population from a declining Varroa-infested colony, effectively establishing first reverse genetic system for an invertebrate RNA virus quasispecies, in order to investigate interactions between the virus genotypes. We demonstrated that individual co-existing DWV genotypes and diverse natural DWV populations replicated equally well indicating that complementation between isolates was not required to enable DWV replication to high levels. Also, no obvious competitive exclusion was detected between genotypes in mixed infections suggesting DWV genotypes are adapted to co-exist to maintain overall population diversity. We suggest that introduction of Varroa resulted in an initial selective sweep of DWV diversity which was followed by DWV diversification driven by selection for new genotypes capable of evading host defenses, specifically antiviral RNA interference.

microbiology↗