Dataset Information

Fertility costs of cryptic viral infections in a model social insect.

ABSTRACT: Declining insect populations emphasize the importance of understanding the drivers underlying reductions in insect fitness. Here, we investigated viruses as a threat to social insect reproduction, using honey bees as a model species. We report that in two independent surveys (N = 93 and N = 54, respectively) of honey bee (Apis mellifera) queens taken from a total of ten beekeeping operations across British Columbia, high levels of natural viral infection are associated with decreased ovary mass. Failed (poor quality) queens displayed higher levels of viral infection, reduced sperm viability, smaller ovaries, and altered ovary protein composition compared to healthy queens. We experimentally infected queens with Israeli acute paralysis virus (IAPV) and found that the ovary masses of IAPV-injected queens were significantly smaller than control queens, demonstrating a causal relationship between viral infection and ovary size. Queens injected with IAPV also had significantly lower expression of vitellogenin, the main source of nutrition deposited into developing oocytes, and higher levels of heat-shock proteins, which are part of the honey bee's antiviral response. This work together shows that viral infections occurring naturally in the field are compromising queen reproductive success.

SUBMITTER: Chapman A

PROVIDER: S-EPMC9508145 | biostudies-literature | 2022 Sep

REPOSITORIES: biostudies-literature

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Fertility costs of cryptic viral infections in a model social insect.

Chapman Abigail A Amiri Esmaeil E Han Bin B McDermott Erin E Rueppell Olav O Tarpy David R DR Foster Leonard J LJ McAfee Alison A

Scientific reports 20220923 1

Declining insect populations emphasize the importance of understanding the drivers underlying reductions in insect fitness. Here, we investigated viruses as a threat to social insect reproduction, using honey bees as a model species. We report that in two independent surveys (N = 93 and N = 54, respectively) of honey bee (Apis mellifera) queens taken from a total of ten beekeeping operations across British Columbia, high levels of natural viral infection are associated with decreased ovary mass. ...[more]

PMID: 36151143

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Project description:BackgroundThe gut microbiome can influence life history traits associated with host fitness such as fecundity and longevity. In most organisms, these two life history traits are traded-off, while they are positively linked in social insects. In ants, highly fecund queens can live for decades, while their non-reproducing workers exhibit much shorter lifespans. Yet, when fertility is induced in workers by death or removal of the queen, worker lifespan can increase. It is unclear how this positive link between fecundity and longevity is achieved and what role the gut microbiome and the immune system play in this. To gain insights into the molecular regulation of lifespan in social insects, we investigated fat body gene expression and gut microbiome composition in workers of the ant Temnothorax rugatulus in response to an experimental induction of fertility and an immune challenge.ResultsFertile workers upregulated several molecular repair mechanisms, which could explain their extended lifespan. The immune challenge altered the expression of several thousand genes in the fat body, including many immune genes, and, interestingly, this transcriptomic response depended on worker fertility. For example, only fertile, immune-challenged workers upregulated genes involved in the synthesis of alpha-ketoglutarate, an immune system regulator, which extends the lifespan in Caenorhabditis elegans by down-regulating the TOR pathway and reducing oxidant production. Additionally, we observed a dramatic loss in bacterial diversity in the guts of the ants within a day of the immune challenge. Yet, bacterial density did not change, so that the gut microbiomes of many immune challenged workers consisted of only a single or a few bacterial strains. Moreover, the expression of immune genes was linked to the gut microbiome composition, suggesting that the ant host can regulate the microbiome in its gut.ConclusionsImmune system flare-ups can have negative consequence on gut microbiome diversity, pointing to a previously underrated cost of immunity. Moreover, our results provide important insights into shifts in the molecular regulation of fertility and longevity associated with insect sociality.

Project description:BackgroundIn social insects, identical genotypes can show extreme lifespan variation providing a unique perspective on age-associated microbial succession. In honey bees, short- and long-lived host phenotypes are polarized by a suite of age-associated factors including hormones, nutrition, immune senescence, and oxidative stress. Similar to other model organisms, the aging gut microbiota of short-lived (worker) honey bees accrue Proteobacteria and are depleted of Lactobacillus and Bifidobacterium, consistent with a suite of host senescence markers. In contrast, long-lived (queen) honey bees maintain youthful cellular function with much lower expression of oxidative stress genes, suggesting a very different host environment for age-associated microbial succession.ResultsWe sequenced the microbiota of 63 honey bee queens exploring two chronological ages and four alimentary tract niches. To control for genetic and environmental variation, we quantified carbonyl accumulation in queen fat body tissue as a proxy for biological aging. We compared our results to the age-specific microbial succession of worker guts. Accounting for queen source variation, two or more bacterial species per niche differed significantly by queen age. Biological aging in queens was correlated with microbiota composition highlighting the relationship of microbiota with oxidative stress. Queens and workers shared many major gut bacterial species, but differ markedly in community structure and age succession. In stark contrast to aging workers, carbonyl accumulation in queens was significantly associated with increased Lactobacillus and Bifidobacterium and depletion of various Proteobacteria.ConclusionsWe present a model system linking changes in gut microbiota to diet and longevity, two of the most confounding variables in human microbiota research. The pattern of age-associated succession in the queen microbiota is largely the reverse of that demonstrated for workers. The guts of short-lived worker phenotypes are progressively dominated by three major Proteobacteria, but these same species were sparse or significantly depleted in long-lived queen phenotypes. More broadly, age-related changes in the honey bee microbiota reflect the regulatory anatomy of reproductive host metabolism. Our synthesis suggests that the evolution of colony-level reproductive physiology formed the context for host-microbial interactions and age-related succession of honey bee microbiota.

Project description:The exoskeleton gives to insects its shape, waterproofing and a range of other roles, besides serving as means of locomotion, the motor function being accomplished by the attachment of somatic muscles. Exoskeleton is renewed every time the insect molts under the control of ecdysteroid hormones. The last molt, which in the holometabolous transforms pupae in adults, involves biosynthesis of the definitive exoskeleton by the subjacent epidemis, followed by progressive differentiation. We used whole genome-based oligonucleotide microarray hybridization and RNA extracted from the honey bee thoracic dorsum, at three time-points of the pupal-to-adult molt, as a strategy to screen genes involved in exoskeleton formation. Gene ontology analysis separated the differentially expressed genes (DEGs) in distinct Biological Processes and Molecular Functions dependently on the time-point approached, thus revealing the functional categories required for adult exoskeleton formation. Approximately 546 of a list of 1253 unique DEGs were up-regulated in the thoracic dorsum during adult cuticle formation, including 23 among the 24 identified cuticle protein (CP) genes, and 29 muscle-related genes. Conserved sequence motifs allowed to include the CP genes in the CPR, Tweedle, Apidermin, CPF, CPLCP1 and Analogous-to-Peritrophins families. Two genes, which do not pertain to any known CP families, were abundantly expressed in the epidermis during adult cuticle formation as shown by in situ hybridization, thus strongly suggesting that they are genuine CP genes. The search for cis-regulatory motifs in the 5M-bM-^@M-^Yuntranslated region of the DEGs revealed potential binding sites for known transcript factors. Several of them were shared by CP genes and thoracic muscle genes, thus allowing to infer that they are co-regulated during differentiation of the thoracic exoskeleton. Together, these data add new information on molecular aspects of exoskeleton formation in the context of the ecdysteroid-coordinated pupal-to-adult molt. The microarray experiments compared differential gene expression in the thoracic integuments of newly-ecdysed pupae (Pw phase), pupae-in-apolysis (Pp phase) and pharate-adults (Pbl phase) collected at the same time from a single honey bee colony. Two separate pools of 10 thoracic integuments each were prepared for each developmental phase (Pw, Pp and Pbl). Dye swaps were done for each comparison and two slides were used to evaluate the differential expression.

Project description:The exoskeleton gives to insects its shape, waterproofing and a range of other roles, besides serving as means of locomotion, the motor function being accomplished by the attachment of somatic muscles. Exoskeleton is renewed every time the insect molts under the control of ecdysteroid hormones. The last molt, which in the holometabolous transforms pupae in adults, involves biosynthesis of the definitive exoskeleton by the subjacent epidemis, followed by progressive differentiation. We used whole genome-based oligonucleotide microarray hybridization and RNA extracted from the honey bee thoracic dorsum, at three time-points of the pupal-to-adult molt, as a strategy to screen genes involved in exoskeleton formation. Gene ontology analysis separated the differentially expressed genes (DEGs) in distinct Biological Processes and Molecular Functions dependently on the time-point approached, thus revealing the functional categories required for adult exoskeleton formation. Approximately 546 of a list of 1253 unique DEGs were up-regulated in the thoracic dorsum during adult cuticle formation, including 23 among the 24 identified cuticle protein (CP) genes, and 29 muscle-related genes. Conserved sequence motifs allowed to include the CP genes in the CPR, Tweedle, Apidermin, CPF, CPLCP1 and Analogous-to-Peritrophins families. Two genes, which do not pertain to any known CP families, were abundantly expressed in the epidermis during adult cuticle formation as shown by in situ hybridization, thus strongly suggesting that they are genuine CP genes. The search for cis-regulatory motifs in the 5’untranslated region of the DEGs revealed potential binding sites for known transcript factors. Several of them were shared by CP genes and thoracic muscle genes, thus allowing to infer that they are co-regulated during differentiation of the thoracic exoskeleton. Together, these data add new information on molecular aspects of exoskeleton formation in the context of the ecdysteroid-coordinated pupal-to-adult molt.

Dataset Information

Fertility costs of cryptic viral infections in a model social insect.

Publications

Fertility costs of cryptic viral infections in a model social insect.

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