11 research outputs found
Elevated virulence of an emerging viral genotype as a driver of honeybee loss.
PublishedJournal ArticleEmerging infectious diseases (EIDs) have contributed significantly to the current biodiversity crisis, leading to widespread epidemics and population loss. Owing to genetic variation in pathogen virulence, a complete understanding of species decline requires the accurate identification and characterization of EIDs. We explore this issue in the Western honeybee, where increasing mortality of populations in the Northern Hemisphere has caused major concern. Specifically, we investigate the importance of genetic identity of the main suspect in mortality, deformed wing virus (DWV), in driving honeybee loss. Using laboratory experiments and a systematic field survey, we demonstrate that an emerging DWV genotype (DWV-B) is more virulent than the established DWV genotype (DWV-A) and is widespread in the landscape. Furthermore, we show in a simple model that colonies infected with DWV-B collapse sooner than colonies infected with DWV-A. We also identify potential for rapid DWV evolution by revealing extensive genome-wide recombination in vivo The emergence of DWV-B in naive honeybee populations, including via recombination with DWV-A, could be of significant ecological and economic importance. Our findings emphasize that knowledge of pathogen genetic identity and diversity is critical to understanding drivers of species decline.This work was supported by the Federal Ministry of Food,
Agriculture and Consumer Protection (Germany): Fit Bee project
(grant 511-06.01-28-1-71.007-10), the EU: BeeDoc (grant 244956),
iDiv (2013 NGS-Fast Track grant W47004118) and the Insect Pollinators
Initiative (IPI grant BB/I000100/1 and BB/I000151/1). The IPI is
funded jointly by the Biotechnology and Biological Sciences Research
Council, the Department for Environment, Food and Rural Affairs,
the Natural Environment Research Council, the Scottish Government
and the Wellcome Trust, under the Living with Environmental
Change Partnership
Unity in defence: honeybee workers exhibit conserved molecular responses to diverse pathogens
This is the final version of the article. Available from the publisher via the DOI in this record.Background: Organisms typically face infection by diverse pathogens, and hosts are thought to have developed specific responses to each type of pathogen they encounter. The advent of transcriptomics now makes it possible to test this hypothesis and compare host gene expression responses to multiple pathogens at a genome-wide scale. Here, we performed a meta-analysis of multiple published and new transcriptomes using a newly developed bioinformatics approach that filters genes based on their expression profile across datasets. Thereby, we identified common and unique molecular responses of a model host species, the honey bee (Apis mellifera), to its major pathogens and parasites: the Microsporidia Nosema apis and Nosema ceranae, RNA viruses, and the ectoparasitic mite Varroa destructor, which transmits viruses.
Results:
We identified a common suite of genes and conserved molecular pathways that respond to all investigated pathogens, a result that suggests a commonality in response mechanisms to diverse pathogens. We found that genes differentially expressed after infection exhibit a higher evolutionary rate than non-differentially expressed genes. Using our new bioinformatics approach, we unveiled additional pathogen-specific responses of honey bees; we found that apoptosis appeared to be an important response following microsporidian infection, while genes from the immune signalling pathways, Toll and Imd, were differentially expressed after Varroa/virus infection. Finally, we applied our bioinformatics approach and generated a gene co-expression network to identify highly connected (hub) genes that may represent important mediators and regulators of anti-pathogen responses.
Conclusions:
Our meta-analysis generated a comprehensive overview of the host metabolic and other biological processes that mediate interactions between insects and their pathogens. We identified key host genes and pathways that respond to phylogenetically diverse pathogens, representing an important source for future functional studies as well as offering new routes to identify or generate pathogen resilient honey bee stocks. The statistical and bioinformatics approaches that were developed for this study are broadly applicable to synthesize information across transcriptomic datasets. These approaches will likely have utility in addressing a variety of biological questions.This article is a joint effort of the working group TRANSBEE and an
outcome of two workshops kindly supported by sDiv, the Synthesis
Centre for Biodiversity Sciences within the German Centre for Integrative
Biodiversity Research (iDiv) Halle-Jena-Leipzig, funded by the German Science
Foundation (FZT 118). New datasets were performed thanks to the Insect
Pollinators Initiative (IPI grant BB/I000100/1 and BB/I000151/1), with participation
of the UK-USA exchange funded by the BBSRC BB/I025220/1 (datasets #4,
11 and 14). The IPI is funded jointly by the Biotechnology and Biological
Sciences Research Council, the Department for Environment, Food and Rural
Affairs, the Natural Environment Research Council, the Scottish Government
and the Wellcome Trust, under the Living with Environmental Change
Partnershi
Divergent Macroparasite Infections in Parapatric Swiss Lake-Stream Pairs of Threespine Stickleback (Gasterosteus aculeatus).
Spatial heterogeneity in diversity and intensity of parasitism is a typical feature of most host-parasite interactions, but understanding of the evolutionary implications of such variation is limited. One possible outcome of infection heterogeneities is parasite-mediated divergent selection between host populations, ecotypes or species which may facilitate the process of ecological speciation. However, very few studies have described infections in population-pairs along the speciation continuum from low to moderate or high degree of genetic differentiation that would address the possibility of parasite-mediated divergent selection in the early stages of the speciation process. Here we provide an example of divergent parasitism in freshwater fish ecotypes by examining macroparasite infections in threespine stickleback (Gasterosteus aculeatus) of four Swiss lake systems each harbouring parapatric lake-stream ecotype pairs. We demonstrate significant differences in infections within and between the pairs that are driven particularly by the parasite taxa transmitted to fish from benthic invertebrates. The magnitude of the differences tended to correlate positively with the extent of neutral genetic differentiation between the parapatric lake and stream populations of stickleback, whereas no such correlation was found among allopatric populations from similar or contrasting habitats. This suggests that genetic differentiation is unrelated to the magnitude of parasite infection contrasts when gene flow is constrained by geographical barriers while in the absence of physical barriers, genetic differentiation and the magnitude of differences in infections tend to be positively correlated
Impact of asynchronous emergence of two lethal pathogens on amphibian assemblages
Emerging diseases have been increasingly associated with population declines, with co-infections
exhibiting many types of interactions. The chytrid fungus (Batrachochytrium dendrobatidis) and
ranaviruses have extraordinarily broad host ranges, however co-infection dynamics have been largely
overlooked. We investigated the pattern of co-occurrence of these two pathogens in an amphibian
assemblage in Serra da Estrela (Portugal). The detection of chytridiomycosis in Portugal was linked
to population declines of midwife-toads (Alytes obstetricans). The asynchronous and subsequent
emergence of a second pathogen - ranavirus - caused episodes of lethal ranavirosis. Chytrid effects
were limited to high altitudes and a single host, while ranavirus was highly pathogenic across multiple
hosts, life-stages and altitudinal range. This new strain (Portuguese newt and toad ranavirus â member
of the CMTV clade) caused annual mass die-offs, similar in host range and rapidity of declines to other
locations in Iberia affected by CMTV-like ranaviruses. However, ranavirus was not always associated
with disease, mortality and declines, contrasting with previous reports on Iberian CMTV-like ranavirosis.
We found little evidence that pre-existing chytrid emergence was associated with ranavirus and the
emergence of ranavirosis. Despite the lack of cumulative or amplified effects, ranavirus drove declines
of host assemblages and changed host community composition and structure, posing a grave threat to
all amphibian populations