Common frog (Rana temporaria) transcriptomes following Exposure to Ranavirus and Batrachochytrium dendrobatidis
ABSTRACT: This experiment examined the transcriptional response of juvenile amphibian hosts (common frog, Rana temporaria) to two important amphibian pathogens: Batrachochytrium dendrobatidis (Bd) and Ranavirus. Common frogs are non-model organisms which do not have a reference genome.
Project description:Amphibian populations around the world are threatened by an emerging infectious pathogen, the chytrid fungus Batrachochytrium dendrobatidis (Bd). How can a fungal skin infection kill such a broad range of amphibian hosts? And why are certain species particularly susceptible to the impacts of Bd? Here we use a genomics approach to understand the genetic response of multiple susceptible frog species to Bd infection. We characterize the transcriptomes of two closely-related endangered frog species (Rana muscosa and Rana sierrae) and analyze whole genome expression profiles from frogs in controlled Bd-infection experiments. We integrate the Rana results with a comparable dataset from a more distantly-related susceptible species (Silurana tropicalis). We demonstrate that Bd-infected frogs show massive disruption of skin function and show no evidence of a robust immune response. The genetic response to infection is shared across the focal susceptible species, suggesting a common effect of Bd on susceptible frogs. A total of five (12-plex) chips were analyzed from 60 samples comprising 2 conditions (control and infected), 3 tissues (skin, liver and spleen) and 2 timepoints (early and late). Three biological replicates were used for each condition and tissue at each time point. Twentyfour arrays were analyzed for skin samples, 24 for liver, and 12 for spleen. The same dye, Cy5, was used for all samples.
Project description:Chytridiomycosis is an emerging infectious disease of amphibians caused by the chytrid Batrachochytrium dendrobatidis (Bd). The disease has been associated with global amphibian declines and is driving the species in the wild to extinction. Using DNA microarray technology we have analysed transcriptional changes in Xenopus tropicalis during the course (7 and 42 days) of infection by Bd under warm (26oC) and cold (18oC) temperatures.
Project description:In the past century, recently emerged infectious diseases have become major drivers of species decline and extinction. Amphibian declines have occurred due to the fungal disease chytridiomycosis, which has exacerbated the conservation crisis of this taxonomic group. Biologists are beginning to understand what traits are important for susceptibility to this disease, but more work is needed to determine why some species succumb to disease while others do not. We conducted a laboratory experiment to examine how two toad species respond to infection in controlled environment. We selected two related species thought to differ in susceptibility – Bufo marinus (an invasive and putatively resistant species) and B. boreas (an endangered and putatively susceptible species). We measured infection intensity, body weight, histological changes at the site of infection, and genome-wide gene expression changes using a custom assay developed from transcriptome sequencing. Our results confirmed that the two species differ in susceptibility. The more susceptible species, B. boreas, experienced higher infection intensities, loss in body weight, more dramatic histological changes, and larger perturbations in gene expression. We found key differences in skin expression responses in multiple pathways including up-regulation of skin integrity-related genes in the resistant B. marinus. Together our results show intrinsic differences in host response between related species, which are likely to be an important factor in explaining variation in response to a deadly emerging pathogen in wild populations. We processed 72 tissue samples in total: six biological replicates, three tissue types (ventral skin, liver, spleen), two treatment groups (pathogen exposed, control), and two host species (Bufo marinus, Bufo boreas). The custom Nimblegen microarray design included 135,200 60-bp probes (excluding control probes) targeting 31,367 transcript contigs from Bufo marinus, Bufo boreas, and model species Xenopus tropicalis, with 4 probes per probe-set. We used the 12-plex microarray platform (12 arrays per glass slide). Differential expression analyses were performed separately for each tissue type and host species.
Project description:The impact of pesticides on amphibian metamorphosis may vary depending on developmental stage of individuals during the exposure period. Some anurans experience increased rates of development when exposure to the insecticide carbaryl occurs later in larval development. We exposed developing northern green frog tadpoles (Lithobates clamitans) to a 3 day pulsatile exposure of 1 mg/L carbaryl at 16 weeks relative to the starting free-swimming Gosner stage 25 (Gosner, 1960) and examined treatment effects on brain mRNA abundance profiles of Gosner stage 46 metamorphs using an amphibian cDNA microarray. Five individuals from control non exposed tadpoles and six animals that had been exposed transiently for 3 days to carbaryl at week 16 and allowed to continue development until Gosner stage 46 were randomly selected for analysis of brain mRNA levels evaluated using the MAGEX DNA microarray.
Project description:Pregnane X receptor (PXR) is generally considered the most important sensor of natural and anthropogenic xenobiotics in vertebrates. In Xenopus, however, PXR plays a role in neural development and it is irresponsive to xenobiotics. We report a first broad-spectrum amphibian xenobiotic receptor, which is an ortholog of the mammalian constitutive androstane receptor (CAR). The low basal activity and pronounced responsiveness to activators such as drugs and steroids displayed by the Xenopus CAR resemble PXR, which both trace back to a common ancestor early in the divergence of land vertebrates. The constitutive activity of CAR emerged first in Sauropsida (reptiles and birds) and it is common to all fully terrestrial land vertebrates (Amniota). This activity can be mimicked by humanizing just two amino acids of the Xenopus CAR. These results demonstrate a remarkable plasticity of CAR which enabled its employment as Xenopus xenosensors. They open way to toxicogenomic and bioaugmentation studies in amphibians, a critically endangered taxon of land vertebrates. Taken together, we provide evidence for a much earlier origin of CAR, for its conservation in tetrapods which exceeds that of PXR, and for its remarkable functional plasticity which enabled its role as a PXR-like xenosensor in Amphibia. We used microarrays to detect global transcriptional changes in Xenopus laevis livers following pregnenolone and artemisinin treatment in order to identify target genes of xlCAR. Arteminisin or pregnenolone were injected intraperitoneally into three frogs on two consecutive days. The control group received in parallel two DMSO injections. All frogs were sacrificed 24 h after the second injection by decapitation, and livers were immediately frozen in liquid nitrogen. After RNA isolation, specimens within the same experimental group were pooled.
Project description:Determining the mechanisms of host-pathogen interaction is critical for understanding and mitigating infectious disease. Mechanisms of fungal pathogenicity are of particular interest given the recent outbreaks of fungal diseases in wildlife populations. Our study focuses on Batrachochytrium dendrobatidis (Bd), the chytrid pathogen responsible for amphibian declines around the world. Previous studies have hypothesized a role for several specific families of secreted proteases as pathogenicity factors in Bd, but the expression of these genes has only been evaluated in laboratory growth conditions. Here we conduct a genome-wide study of Bd gene expression under two different nutrient conditions. We compare Bd gene expression profiles in laboratory growth media and in host tissue (i.e., frog skin). A large proportion of genes in the Bd genome show increased expression when grown in host tissue, indicating the importance of studying pathogens in their infection environment. A number of gene classes show particularly high levels of expression in host tissue, including three families of secreted proteases (metallo-, serine- and aspartyl-proteases), adhesion genes, lipase-3 encoding genes, and a group of phylogenetically unusual crinkler-like effectors. We discuss the roles of these different genes as putative pathogenicity factors and discuss what they can teach us about Bd's metabolic targets, host invasion, and pathogenesis. One 12-plex chip was analyzed from 12 RNA samples extracted from Batrachochytrium dendrobatidis grown in 2 substrates. Six biological replicates were used for each substrate - sterile frog skin and tryptone nutrient broth. The same dye, Cy5, was used for all samples.
Project description:Understanding dynamics of antigen specific B cell responses and link between BCR and B cell differentiation is crucial for our ability to direct immune responses and to generate memory and plasma cells responses to protective targets. Here we have infected mice with IAV-PR8 and sacrificed them at different days after infection (7-14-28). 2 naive mice were used as controls (spleen and lungs). From individual spleen, lungs and mediastinal lymph nodes we have sorted Hemagglutinin (HA)-specific IgD- B cells and single cell sequenced RNA and BCR. We identify several known and novel B cell subpopulations forming after infection and find organ-specific difference that persist over the course of the response. We found important transcriptional differences between memory cells in lungs and immune organs and describe organ-restricted clonal expansion. Strikingly, by combining BCR mutational analysis, monoclonal antibody expression and affinity measurements we found no differences between germinal center (GC)-derived memory and plasma cells, at odds with an affinity-based selection model. These finding provide the most comprehensive picture to date of organ specific antiviral B cell responses, differentiation, clonal-proliferation and dynamics.
Project description:The oomycete P. infestans is the causal agent of late blight, the most devastating potato disease. In contrast to potato, A. thaliana is able to successfully prevent colonization of the pathogen due to a multi-layered nonhost resistance. Several mutants have been isolated which are impaired in penetration resistance. A mutation in the gene PEN2, which encodes for an enzyme involved in indole glucosinolate metabolism (Bednarek et al. (2009)), results in the loss of penetration resistance against P. infestans (Lipka et al. (2005)). Despite its ability to penetrate epidermal cells of pen2 mutant plants, P. infestans is still not able to colonize these plants. Additional mutants were isolated by Kopischke et al. (2013) which show enhanced defense responses upon infection with P. infestans: pen2erp1 and pen2erp2, and backcrossed mutants erp140 and erp2D. We used six different plant lines, the wildtype-like gl1, and the five different mutants (pen2, pen2erp1, pen2erp2, erp2D, erp140). The plants were either infected with P. infestans spores or treated with water as control, and harvested 6h and 12h after treatment. The experiment was repeated three times with different P. infestans cultures, resulting in biological triplicates, for an overall of 6 x 2 x 2 x 3 = 72 samples. A metabolomics data set from the same set of samples has been submitted to MetaboLights database at EMBL-EBI (http://www.ebi.ac.uk/metabolights/index) under accession number MTBLS18 .
Project description:Endocrine disruption (ED) can trigger far-reaching effects on environmental populations, justifying a refusal of market approval for chemicals with ED properties. For the assessment of ED effects on the thyroid system, regulatory decisions mostly rely on amphibian studies. Here we present a rapid and reproducible data dependent proteomics approach for identifying comprehensive molecular signatures of interference with the thyroid system in zebrafish (Danio rerio) embryos as an alternative to animal testing. For this, we have analysed the thyroid hormone thyronin (T3) as model substances for thyroidal activity in a modified zebrafish embryo toxicity test (zFET). These fingerprints allow for a definition of solid biomarkers as tools in screening approaches and for integration in chronic toxicity studies for suspect substances, such as the fish early life-stage test (OECD TG 210).