Nurit Eliash - Academia.edu (original) (raw)

Papers by Nurit Eliash

BMC Biology

Background Vector-borne viral diseases threaten human and wildlife worldwide. Vectors are often v... more Background Vector-borne viral diseases threaten human and wildlife worldwide. Vectors are often viewed as a passive syringe injecting the virus. However, to survive, replicate and spread, viruses must manipulate vector biology. While most vector-borne viral research focuses on vectors transmitting a single virus, in reality, vectors often carry diverse viruses. Yet how viruses affect the vectors remains poorly understood. Here, we focused on the varroa mite (Varroa destructor), an emergent parasite that can carry over 20 honey bee viruses, and has been responsible for colony collapses worldwide, as well as changes in global viral populations. Co-evolution of the varroa and the viral community makes it possible to investigate whether viruses affect vector gene expression and whether these interactions affect viral epidemiology. Results Using a large set of available varroa transcriptomes, we identified how abundances of individual viruses affect the vector’s transcriptional network. ...

The effect of selected compounds on Varroa host choice between a nurse and a forager bee

A. Experimental setup. The test compound did not contact the mite, an... more A. Experimental setup. The test compound did not contact the mite, and the mite could move around and choose between a freshly killed nurse or forager. B. Effect of cy{4,1}: data are the percentage of Varroa that selected a particular host in the presence of hexane (control) or disrupting compound cy{4,1} at different doses (0.01 µg, 0.1 µg, 10 µg). Numbers within the bars show the number of Varroa choosing each of the hosts. C. Effect of 3b{2,2}. D. Effect of 3c{2,2}.</p

Electrophysiology with the Varroa foreleg

A. Electrophysiology setup of an isolated Varroa f... more A. Electrophysiology setup of an isolated Varroa foreleg that was stimulated with the headspace volatiles of freshly caught honey bees in a jar. B. Typical traces of Varroa foreleg responses to air (left) and honey bee volatiles (right). C. Varroa foreleg electrophysiological response amplitude. Comparison between the responses to the headspaces of different numbers of bees: no bee (empty jar), 1, 5 and 10 bees. ANOVA repeated measures: bars marked by different letters are significantly different, p<0.05, n = 6.</p

The effect of selected compounds on Varroa ability to reach any host

Effect of 3 selected compounds on the percentage of mites reaching any of the hosts in t... more Effect of 3 selected compounds on the percentage of mites reaching any of the hosts in the choice bioassay, 180 min from the beginning of the experiment. The data are percentage of viable mites in the presence of hexane (control) or disrupting compound at each of three tested doses (0.01 µg, 0.1 µg, 10 µg) Chi-square test, ns.</p

Active space and structure-activity of host choice alteration activity

A. Overlay of energy minimized conformers of cy{&l... more A. Overlay of energy minimized conformers of cy{4,1} and 3b{2,2}. The Connolly molecular surface of the overlaid molecules is shown in light blue. Hydrogen atoms and lone pairs have been omitted on the structures, but are included in the surfaces. Distances: a∼8.6 Å, b∼10 Å, c∼8.5 Å, d∼6.9 Å, e∼5.9 Å. B and C. Examples of the two structure-activity correlations found. B. Correlation between the highest occupied molecular orbital (HOMO) energy and the difference in short-term inhibition (%) between the “Bee before” and “Bee + compound” treatments (Δ STI (%)). Only the aromatic compounds (3c series, 3a{2,2}, 3b{2,2} and DEET) are included. C. Correlation between the polar accessible surface area (ASA_P) and the difference in long-term inhibition (%) between the “Bee before” and “Bee after” treatments (Δ LTI (%)).</p

Detailed evaluation of the long-term inhibitory effect of the most active compounds

The effect of 0.1 µg cy{4,1} (A... more The effect of 0.1 µg cy{4,1} (A) or 3b{2,2} (B), with and without a simultaneous stimulus of the headspace volatiles from 5 nurse bees, on the electrophysiological response of the Varroa foreleg. The data are normalized values (%, average+SE): bars marked by different letters are significantly different, ANOVA repeated measures, p<0.05, p<0.05, n = 6. The longevity of the inhibitory effect of 0.1 µg cy{4,1} (C) or 0.1 µg 3b{2,2} (D) on Varroa foreleg electrophysiological responses. The time interval between the mixed stimulus (Bee + compound) and the pure bee stimulus was varied. Values are normalized against the response to air (%, average+SE): bars marked by different letters are significantly different, ANOVA repeated measures, p<0.05; n = 6.</p

Dose responses of long-term inhibitory compounds cy{4,1}, 3b{2,2} and cy{2,2}

The responses of the Varroa forelegs to stimulation with different am... more The responses of the Varroa forelegs to stimulation with different amounts of each compound and with the headspace from 5 nurse bees (normalized values against the response to air %, average+SE). Bars within each dose, marked by different letters, are significantly different, ANOVA repeated measures, p<0.05, n = 7.</p

Electrophysiological screening of the compounds

A. Order of the Varroa foreleg stimulations and te... more A. Order of the Varroa foreleg stimulations and terminology used for the corresponding responses. The time interval between each stimulus was 30 s, unless otherwise stated. The stimuli were: Air, Headspace of five nurse bees (bee stimulus), Bee stimulus together with the compound (Bee stimulus + comp) or of the hexane control (Bee stimulus + hexane). In italics, below the stimuli, are the names of the values presented in the results. B. Initial screen of the Varroa foreleg electrophysiological response to different stimuli, all loaded at 10 µg in the stimulus cartridge (normalized values against the response to air %, average+SE). For the bee stimuli, the headspace from 5 nurse bees was used. Bars marked by different letters are significantly different, ANOVA repeated measures, p<0.05, n = 10.C. Testing of the individual components of the blend HCO-2169 at 10 µg doses (n = 10). D. Experiment with the three isomers of diethyoxybenzene at 10 µg doses (n = 6).</p

Compounds used in this study

A. Structures of the dialkoxybenzenes; their codenames are explained ... more A. Structures of the dialkoxybenzenes; their codenames are explained in ref <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0106889#pone.0106889-Paduraru1" target="_blank">[17]</a>. B. Structures of the 5(2′-methoxyethyl) cyclopent-2-en-1-alkoxy diethers (cy{R1,1} compounds). C. Synthesis of the cy{R1,1} compounds. Abbreviations: rt = room temperature; TBDMSCl = tert-butyl dimethylsilyl chloride; THF = tetrahydrofuran.</p

bioRxiv, 2021

Vector-borne viral diseases threaten human and wildlife worldwide. Vectors are often viewed as a ... more Vector-borne viral diseases threaten human and wildlife worldwide. Vectors are often viewed as a passive syringe injecting the virus, however to survive, replicate and spread, viruses must manipulate vector biology. While most vector-borne viral research focuses on vectors transmitting a single virus, in reality vectors often carry diverse viruses. Yet how viruses affect the vectors remains poorly understood. Here we focused on the varroa mite, an emergent parasite that vectors over 20 honey bee viruses, and has been responsible for colony collapses worldwide, as well as changes in global viral populations. Co-evolution of the varroa and the viral community makes it possible to investigate whether viruses affect vector gene expression, and whether these interactions affect viral epidemiology. Using a large set of available varroa transcriptomes we identified how abundances of individual viruses affect the vector’s transcriptional network. Perhaps surprisingly, we found no evidence o...

Nowadays, commercial mass rearing of honeybee queens combined with their storage in cages or in m... more Nowadays, commercial mass rearing of honeybee queens combined with their storage in cages or in mating hives (ca. 2500 bees) is a standard procedure, particularly in Central Europe, e.g. in Poland. The cage environment, however, is significantly different from the hive one. It may be assumed that the commercial intensification of queen rearing, particularly the cage storage of queens, leads to reduction in their quality, including their biochemical defense system, which comprises, i.a. the hemolymph antioxidant system. The aim of the research was to determine enzymatic antioxidant activities (SOD (superoxide dismutase) and CAT (catalase)) and TAC (total antioxidant capacity) levels in the hemolymph of 8-dayold virgin queens which had been kept in queen cages or in mating hives from their emergence. Two queen groups were created on the day of their emergence. In the first one, the queens (n = 70) were individually placed into 70 queen cages, 10 worker bees with candy in each, and kep...

Olfaction as a Target for Control of Honeybee Parasite Mite Varroa destructor

Olfactory Concepts of Insect Control - Alternative to insecticides, 2019

The mite Varroa destructor Anderson & Trueman (Acari: Varroidae) is a major global threat to ... more The mite Varroa destructor Anderson & Trueman (Acari: Varroidae) is a major global threat to the European honeybee Apis mellifera. The mite is an obligatory ectoparasite. It feeds on the hemolymph of bees and also serves as an active vector for pathogenic viruses, which have become more abundant and virulent since the invasion of the mite. The Varroa life cycle is tightly linked to that of a honeybee. The cycle can be generally divided into two main phases: a reproductive phase, in which the female Varroa parasitizes bee pupae and reproduce within sealed brood cells, and a phoretic phase, in which it parasitizes adult bees. Between these phases Varroa mites can wander on comb surfaces. Hive volatiles, mainly from adult bees and brood, play a crucial role in the parasite’s life cycle, by guiding host finding, selection and regulating its reproduction suggesting that the mite’s olfaction may be an important target for new specific control agents. This concept was proven with some synthetic volatile compounds. Inhibition of host sensing leads to incorrect Varroa host selection or reduction in mite’s ability to reach a host. Although the mode of action of these compounds is not yet clear, this approach seems promising towards an integrated and sustainable control over this major apicultural pest.

Apidologie, 2020

The ectoparasitic mite, Varroa destructor Anderson and Trueman (Acar: Varroidae), is a major thre... more The ectoparasitic mite, Varroa destructor Anderson and Trueman (Acar: Varroidae), is a major threat for the honey bee, Apis mellifera L. Varroa behavior and physiology are influenced by compounds produced by the honey bee, as well as cues from the general colony environment. As part of our effort to disrupt varroa host chemosensing, we tested 1-allyloxy-4-propoxybenzene, 3c {3,6 }, a known feeding deterrent of Lepidoptera larvae and a repellent of mosquitoes of similar activity to DEET. Its effect on varroa mites was evaluated by electrophysiological and behavioral bioassays. Its effect on honey bee chemosensing was also assessed. Compound 3c{ 3,6 } is sensed by honey bees, but the detection of the compound alone by varroa is not clear. The electrophysiological study showed that 3c{ 3,6 } decreases the varroa foreleg responses towards head space odor of nurse bees. However, the response of honey bee antennae towards nurse bee head space odor was not affected. Consistent with electrophysiological studies, in the presence of 3c{ 3,6 } , the ability of varroa to reach any host decreased at the end of the experiment. No lethal effect to the honey bees was recorded. These data showed that 3c{ 3,6 } affects the peripheral olfactory system of varroa by disrupting the chemical recognition process. invertebrate chemoreception / host detection / olfaction / dialkoxybenzene / host choice

Current Opinion in Insect Science, 2020

While ectoparasitic Varroa mites cause minimal damage to their co-evolved ancestral host, the eas... more While ectoparasitic Varroa mites cause minimal damage to their co-evolved ancestral host, the eastern honey bee (Apis cerana), they devastate their novel host, the western 20 honey bee (Apis mellifera). The host switch caused worldwide population collapses, threatening global food security. Varroa management strategies have focused on breeding for bees for tolerance. But, can Varroa overcome these counter-adaptations in a classic coevolutionary arms race? Despite increasing evidence for Varroa genetic diversity and evolvability, this eventuality has largely been neglected. We therefore suggest a 25 more holistic paradigm for studying this host-parasite interaction, in which 'Varroatolerant' bee traits should be viewed as a shared phenotype resulting from Varroa and honey bee interaction.

Varroa chemosensory proteins: some are conserved across Arthropoda but others are arachnid specific

Insect Molecular Biology, 2018

The tight synchronization between the life cycle of the obligatory parasitic mite Varroa destruct... more The tight synchronization between the life cycle of the obligatory parasitic mite Varroa destructor (Varroa) and its host, the honeybee, is mediated by honeybee chemical stimuli. These stimuli are mainly perceived by a pit organ located at the distal part of the mite&amp;#39;s foreleg. In the present study, we searched for Varroa chemosensory molecular components by comparing transcriptomic and proteomic profiles between forelegs from different physiological stages, and rear legs. In general, a comparative transcriptomic analysis showed a clear separation of the expression profiles between the rear legs and the three groups of forelegs (phoretic, reproductive and tray-collected mites). Most of the differentially expressed transcripts and proteins in the mite&amp;#39;s foreleg were previously uncharacterized. Using a conserved domain approach, we identified 45 transcripts with known chemosensory domains belonging to seven chemosensory protein families, of which 16 were significantly up regulated in the mite&amp;#39;s forelegs when compared to rear legs. These are soluble and membrane bound proteins, including the somewhat ignored receptors of degenerin/epithelial Na+ channels (ENaCs) and transient receptor potentials (TRPs). Phylogenetic clustering and expression profiles of the putative chemosensory proteins, suggest their role in chemosensation and shed light on the evolution of these proteins in Chelicerata. This article is protected by copyright. All rights reserved.

Scientific reports, Jan 12, 2017

Chemosensing is a primary sense in nature, however little is known about its mechanism in Chelice... more Chemosensing is a primary sense in nature, however little is known about its mechanism in Chelicerata. As a model organism we used the mite Varroa destructor, a key parasite of honeybees. Here we describe a transcriptomic analysis of two physiological stages for the Varroa foreleg, the site of primary olfactory organ. The transcriptomic analysis revealed transcripts of chemosensory related genes belonging to several groups. These include Niemann-Pick disease protein, type C2 (NPC2), gustatory receptors (GRs), ionotropic receptors (IRs), sensory neuron membrane proteins (SNMPs) and odorant binding proteins (OBP). However, no insect odorant receptors (ORs) and odorant co-receptors (ORcos) were found. In addition, we identified a homolog of the most ancient IR co-receptor, IR25a, in Varroa as well as in other members of Acari. High expression of this transcript in the mite's forelegs, while not detectable in the other pairs of legs, suggests a function for this IR25a-like in Varroa...

Apidologie, 2016

Honey bees and their ectoparasite Varroa destructor communicate through chemical signals among th... more Honey bees and their ectoparasite Varroa destructor communicate through chemical signals among themselves, but they also eavesdrop on each other's chemical cues. We summarize semiochemicals of honey bees and Varroa , and their roles in honey bee-Varroa interactions. We also give an overview of current Varroa control methods, which can be classified into three categories: (1) chemical control methods with acaricides, (2) biotechnical intervention, and (3) bee breeding programs. Widely used synthetic chemical acaricides are failing due to the emergence of resistant mites. Therefore, new methods are being sought for Varroa control, and methods that target the semiochemical interactions between bees and mites are among the candidates. We review our discovery of compounds that alter the host choice of Varroa mites (from nurse to forager) in laboratory tests. Any semiochemicalbased methods are still in the experimental stage and need validation in the field.

Identification and gene-silencing of a putative odorant receptor transcription factor in Varroa destructor: possible role in olfaction

Insect molecular biology, Jan 23, 2016

The ectoparasitic mite Varroa destructor is one of the major threats to apiculture. Using a behav... more The ectoparasitic mite Varroa destructor is one of the major threats to apiculture. Using a behavioural choice bioassay, we determined that phoretic mites were more successful in reaching a bee than reproductive mites, suggesting an energy trade-off between reproduction and host selection. We used both chemo-ecological and molecular strategies to identify the regulation of the olfactory machinery of Varroa and its association with reproduction. We focused on transcription regulation. Using primers designed to the conserved DNA binding region of transcription factors, we identified a gene transcript in V. destructor homologous to the pheromone receptor transcription factor (PRTF) gene of Pediculus humanus corporis. Quantitative PCR (qPCR) revealed that this PRTF-like gene transcript is expressed in the forelegs at higher levels than in the body devoid of forelegs. Subsequent comparative qPCR analysis showed that transcript expression was significantly higher in the phoretic as compar...

Apidologie, 2014

Varroa destructor Anderson and Trueman (Acari: Varroidae) is an obligatory ectoparasitic mite of ... more Varroa destructor Anderson and Trueman (Acari: Varroidae) is an obligatory ectoparasitic mite of honey bees. In view of limited success in mite control, the use of synthetic repellent was evaluated. The objective of the present study was to investigate the effect of common arthropod repellent N,N-diethyl-m-toluamide (DEET) on the chemosensing of the V. destructor and its hosts, the European honey bee (Apis mellifera L.), by electrophysiological and behavioural bioassays. In electrophysiological assays, the nurse headspace served as a positive stimulus for the V. destructor foreleg, whereas a queen headspace was used as a positive stimulus for honey bee antennae. Two effects of DEET on V. destructor host chemosensing were evaluated: short-term inhibition and longterm inhibition. The inhibition observed in the presence of DEET simultaneously with a positive stimulus was termed "short term inhibition", while inhibition that occurred following the administration of the compound alone was termed "long term inhibition". In V. destructor , DEET served as a long-term inhibitor to the response of the chemosensory organ to nurse bee headspace volatiles, whereas in honey bee, it caused short-term inhibition of antenna response to queen volatiles. Consistent with electrophysiological studies, DEET significantly inhibited host choice of mites, whereas even a 10 times higher dose did not alter honey bee behaviours (e.g. antennating, grooming, fanning etc.) or worker attraction to a queen. These data suggest that DEET may selectively disrupt the honey bee chemosensing of V. destructor.