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:Emerging infectious diseases are of great concern for both wildlife and humans. Several highly virulent fungal pathogens have recently been discovered in natural populations, highlighting the need for a better understanding of fungal-vertebrate host-pathogen interactions. Because most fungal pathogens are not fatal in the absence of other predisposing conditions, host-pathogen dynamics for deadly fungal pathogens are of particular interest. The chytrid fungus Batrachochytrium dendrobatidis (hereafter Bd) infects hundreds of species of frogs in the wild. It is found worldwide and is a significant contributor to the current global amphibian decline. However, the mechanism by which Bd causes death in amphibians, and the response of the host to Bd infection, remain largely unknown. Here we use whole-genome microarrays to monitor the transcriptional responses to Bd infection in the model frog species, Silurana (Xenopus) tropicalis, which is susceptible to chytridiomycosis. To elucidate the immune response to Bd and evaluate the physiological effects of chytridiomycosis, we measured gene expression changes in several tissues (liver, skin, spleen) following exposure to Bd. We detected a strong transcriptional response for genes involved in physiological processes that can help explain some clinical symptoms of chytridiomycosis at the organismal level. However, we detected surprisingly little evidence of an immune response to Bd exposure, suggesting that this susceptible species may not be mounting efficient innate and adaptive immune responses against Bd. The weak immune response may be partially explained by the thermal conditions of the experiment, which were optimal for Bd growth. However, many immune genes exhibited decreased expression in Bd-exposed frogs compared to control frogs, suggesting a more complex effect of Bd on the immune system than simple temperature-mediated immune suppression. This study generates important baseline data for ongoing efforts to understand differences in response to Bd between susceptible and resistant frog species and the effects of chytridiomycosis in natural populations.
Project description:Naphthenic acids (Nas) are carboxylic acids present in crude oil and classfied as emergent pollutants. The mechanisms underlaying the toxicity of such mixtures are unknown. Changes in gene expression are expected to reflect te teratogenenic effects of the exposure to NAs. The objective of these experiments is to determine the changes in the gene expression profile of Silurana (Xenopus) tropicalis embryos due to the exposition to two NA mixtures.
