Dataset Information

Immune related gene expression in worker honey bee (Apis mellifera carnica) pupae exposed to neonicotinoid thiamethoxam and Varroa mites (Varroa destructor).

ABSTRACT: Varroa destructor is one of the most common parasites of honey bee colonies and is considered as a possible co-factor for honey bee decline. At the same time, the use of pesticides in intensive agriculture is still the most effective method of pest control. There is limited information about the effects of pesticide exposure on parasitized honey bees. Larval ingestion of certain pesticides could have effects on honey bee immune defense mechanisms, development and metabolic pathways. Europe and America face the disturbing phenomenon of the disappearance of honey bee colonies, termed Colony Collapse Disorder (CCD). One reason discussed is the possible suppression of honey bee immune system as a consequence of prolonged exposure to chemicals. In this study, the effects of the neonicotinoid thiamethoxam on honey bee, Apis mellifera carnica, pupae infested with Varroa destructor mites were analyzed at the molecular level. Varroa-infested and non-infested honey bee colonies received protein cakes with or without thiamethoxam. Nurse bees used these cakes as a feed for developing larvae. Samples of white-eyed and brown-eyed pupae were collected. Expression of 17 immune-related genes was analyzed by real-time PCR. Relative gene expression in samples exposed only to Varroa or to thiamethoxam or simultaneously to both Varroa and thiamethoxam was compared. The impact from the consumption of thiamethoxam during the larval stage on honey bee immune related gene expression in Varroa-infested white-eyed pupae was reflected as down-regulation of spaetzle, AMPs abaecin and defensin-1 and up-regulation of lysozyme-2. In brown-eyed pupae up-regulation of PPOact, spaetzle, hopscotch and basket genes was detected. Moreover, we observed a major difference in immune response to Varroa infestation between white-eyed pupae and brown-eyed pupae. The majority of tested immune-related genes were upregulated only in brown-eyed pupae, while in white-eyed pupae they were downregulated.

SUBMITTER: Tesovnik T

PROVIDER: S-EPMC5663428 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Immune related gene expression in worker honey bee (Apis mellifera carnica) pupae exposed to neonicotinoid thiamethoxam and Varroa mites (Varroa destructor).

Tesovnik Tanja T Cizelj Ivanka I Zorc Minja M Čitar Manuela M Božič Janko J Glavan Gordana G Narat Mojca M

PloS one 20171031 10

Varroa destructor is one of the most common parasites of honey bee colonies and is considered as a possible co-factor for honey bee decline. At the same time, the use of pesticides in intensive agriculture is still the most effective method of pest control. There is limited information about the effects of pesticide exposure on parasitized honey bees. Larval ingestion of certain pesticides could have effects on honey bee immune defense mechanisms, development and metabolic pathways. Europe and A ...[more]

PMID: 29088251

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Project description:BACKGROUND: The parasitic mite, Varroa destructor, is the most serious pest of the western honey bee, Apis mellifera, and has caused the death of millions of colonies worldwide. This mite reproduces in brood cells and parasitizes immature and adult bees. We investigated whether Varroa infestation induces changes in Apis mellifera gene expression, and whether there are genotypic differences that affect gene expression relevant to the bee's tolerance, as first steps toward unravelling mechanisms of host response and differences in susceptibility to Varroa parasitism. RESULTS: We explored the transcriptional response to mite parasitism in two genetic stocks of A. mellifera which differ in susceptibility to Varroa, comparing parasitized and non-parasitized full-sister pupae from both stocks. Bee expression profiles were analyzed using microarrays derived from honey bee ESTs whose annotation has recently been enhanced by results from the honey bee genome sequence. We measured differences in gene expression in two colonies of Varroa-susceptible and two colonies of Varroa-tolerant bees. We identified a set of 148 genes with significantly different patterns of expression: 32 varied with the presence of Varroa, 116 varied with bee genotype, and 2 with both. Varroa parasitism caused changes in the expression of genes related to embryonic development, cell metabolism and immunity. Bees tolerant to Varroa were mainly characterized by differences in the expression of genes regulating neuronal development, neuronal sensitivity and olfaction. Differences in olfaction and sensitivity to stimuli are two parameters that could, at least in part, account for bee tolerance to Varroa; differences in olfaction may be related to increased grooming and hygienic behavior, important behaviors known to be involved in Varroa tolerance. CONCLUSION: These results suggest that differences in behavior, rather than in the immune system, underlie Varroa tolerance in honey bees, and give an indication of the specific physiological changes found in parasitized bees. They provide a first step toward better understanding molecular pathways involved in this important host-parasite relationship.

Project description:Worldwide, the ecto-parasitic mite Varroa destructor has been assigned as an important driver of honey bee (Apis mellifera) colony losses. Unlike the subspecies of European origin, the honey bees in some African countries such as Uganda and Ethiopia may not be as threatened or suffer less from mite-infestations. However, only little is known about the factors or traits that enable them to co-exist with the mite without beekeepers' intervention. Hence, this study was designed to investigate these factors or traits that limit the Varroa mite population in Ethiopian honey bees (Apis mellifera simensis). The study was conducted in the primary honey producing region of Ethiopia, i.e. Tigray. Mite infestation levels were shown to be lower in traditional hives (when compared to framed hives) and when colonies were started up from swarm catching (when compared to colony splitting). However, the influence of the comb cell size on mite infestation was not observed. With respect to the bee biology, the hygienic behavior was shown to be high (pin-test: 92.2% removal in 24 hours) and was negatively correlated with phoretic mite counts (Pearson; r = -0.79; P < 0.01) and mite infestation levels in brood (Pearson; r = -0.46; P < 0.001). Efforts to estimate the Varroa mite reproductive capacity were seriously hampered by an extremely low brood infestation level. From the 133 founder mites found (in 6727 capped brood cells) only 18.80% were capable of producing a reproductive progeny. Failure to produce adult male progeny was unexpectedly high (79.70%). We have suggested a few adaptations to the test protocols allowing to estimate the protective traits of honey bee colonies under very low Varroa pressure. Apart from that, this study demonstrates that the honey bees from Ethiopia are suitable targets to further decipher the genetic predisposition of resistance against V. destructor. It is still unclear to what extent simensis differs from the more common scutellata subspecies.

Dataset Information

Immune related gene expression in worker honey bee (Apis mellifera carnica) pupae exposed to neonicotinoid thiamethoxam and Varroa mites (Varroa destructor).

Publications

Immune related gene expression in worker honey bee (Apis mellifera carnica) pupae exposed to neonicotinoid thiamethoxam and Varroa mites (Varroa destructor).

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