Dataset Information

Global gene expression profiles for life stages of the deadly amphibian pathogen Batrachochytrium dendrobatidis.

ABSTRACT: Amphibians around the world are being threatened by an emerging pathogen, the chytrid fungus Batrachochytrium dendrobatidis (Bd). Despite intensive ecological study in the decade since Bd was discovered, little is known about the mechanism by which Bd kills frogs. Here, we compare patterns of global gene expression in controlled laboratory conditions for the two phases of the life cycle of Bd: the free-living zoospore and the substrate-embedded sporangia. We find zoospores to be transcriptionally less complex than sporangia. Several transcripts more abundant in zoospores provide clues about how this motile life stage interacts with its environment. Genes with higher levels of expression in sporangia provide new hypotheses about the molecular pathways involved in metabolic activity, flagellar function, and pathogenicity in Bd. We highlight expression patterns for a group of fungalysin metallopeptidase genes, a gene family thought to be involved in pathogenicity in another group of fungal pathogens that similarly cause cutaneous infection of vertebrates. Finally we discuss the challenges inherent in developing a molecular toolkit for chytrids, a basal fungal lineage separated by vast phylogenetic distance from other well characterized fungi.

SUBMITTER: Rosenblum EB

PROVIDER: S-EPMC2566996 | biostudies-literature | 2008 Nov

REPOSITORIES: biostudies-literature

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Global gene expression profiles for life stages of the deadly amphibian pathogen Batrachochytrium dendrobatidis.

Rosenblum Erica Bree EB Stajich Jason E JE Maddox Nicole N Eisen Michael B MB

Proceedings of the National Academy of Sciences of the United States of America 20081013 44

Amphibians around the world are being threatened by an emerging pathogen, the chytrid fungus Batrachochytrium dendrobatidis (Bd). Despite intensive ecological study in the decade since Bd was discovered, little is known about the mechanism by which Bd kills frogs. Here, we compare patterns of global gene expression in controlled laboratory conditions for the two phases of the life cycle of Bd: the free-living zoospore and the substrate-embedded sporangia. We find zoospores to be transcriptionall ...[more]

PMID: 18852473

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Project description:Projected changes in climate conditions are emerging as significant risk factors to numerous species, affecting habitat conditions and community interactions. Projections suggest species range shifts in response to climate change modifying environmental suitability and is supported by observational evidence. Both pathogens and their hosts can shift ranges with climate change. We consider how climate change may influence the distribution of the emerging infectious amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), a pathogen associated with worldwide amphibian population losses. Using an expanded global Bd database and a novel modeling approach, we examined a broad set of climate metrics to model the Bd-climate niche globally and regionally, then project how climate change may influence Bd distributions. Previous research showed that Bd distribution is dependent on climatic variables, in particular temperature. We trained a machine-learning model (random forest) with the most comprehensive global compilation of Bd sampling records (~5,000 site-level records, mid-2014 summary), including 13 climatic variables. We projected future Bd environmental suitability under IPCC scenarios. The learning model was trained with combined worldwide data (non-region specific) and also separately per region (region-specific). One goal of our study was to estimate of how Bd spatial risks may change under climate change based on the best available data. Our models supported differences in Bd-climate relationships among geographic regions. We projected that Bd ranges will shift into higher latitudes and altitudes due to increased environmental suitability in those regions under predicted climate change. Specifically, our model showed a broad expansion of areas environmentally suitable for establishment of Bd on amphibian hosts in the temperate zones of the Northern Hemisphere. Our projections are useful for the development of monitoring designs in these areas, especially for sensitive species and those vulnerable to multiple threats.

Project description:The rapid worldwide emergence of the amphibian pathogen Batrachochytrium dendrobatidis (Bd) is having a profound negative impact on biodiversity. However, global research efforts are fragmented and an overarching synthesis of global infection data is lacking. Here, we provide results from a community tool for the compilation of worldwide Bd presence and report on the analyses of data collated over a four-year period. Using this online database, we analysed: 1) spatial and taxonomic patterns of infection, including amphibian families that appear over- and under-infected; 2) relationships between Bd occurrence and declining amphibian species, including associations among Bd occurrence, species richness, and enigmatic population declines; and 3) patterns of environmental correlates with Bd, including climate metrics for all species combined and three families (Hylidae, Bufonidae, Ranidae) separately, at both a global scale and regional (U.S.A.) scale. These associations provide new insights for downscaled hypothesis testing. The pathogen has been detected in 52 of 82 countries in which sampling was reported, and it has been detected in 516 of 1240 (42%) amphibian species. We show that detected Bd infections are related to amphibian biodiversity and locations experiencing rapid enigmatic declines, supporting the hypothesis that greater complexity of amphibian communities increases the likelihood of emergence of infection and transmission of Bd. Using a global model including all sampled species, the odds of Bd detection decreased with increasing temperature range at a site. Further consideration of temperature range, rather than maximum or minimum temperatures, may provide new insights into Bd-host ecology. Whereas caution is necessary when interpreting such a broad global dataset, the use of our pathogen database is helping to inform studies of the epidemiology of Bd, as well as enabling regional, national, and international prioritization of conservation efforts. We provide recommendations for adaptive management to enhance the database utility and relevance.

Project description:UnlabelledBatrachochytrium dendrobatidis is the causative agent of chytridiomycosis, which is considered one of the driving forces behind the worldwide decline in populations of amphibians. As a member of the phylum Chytridiomycota, B. dendrobatidis has diverged significantly to emerge as the only pathogen of adult vertebrates. Such shifts in lifestyle are generally accompanied by various degrees of genomic modifications, yet neither its mode of pathogenicity nor any factors associated with it have ever been identified. Presented here is the identification and characterization of a unique expansion of the carbohydrate-binding module family 18 (CBM18), specific to B. dendrobatidis. CBM (chitin-binding module) expansions have been likened to the evolution of pathogenicity in a variety of fungus species, making this expanded group a prime candidate for the identification of potential pathogenicity factors. Furthermore, the CBM18 expansions are confined to three categories of genes, each having been previously implicated in host-pathogen interactions. These correlations highlight this specific domain expansion as a potential key player in the mode of pathogenicity in this unique fungus. The expansion of CBM18 in B. dendrobatidis is exceptional in its size and diversity compared to other pathogenic species of fungi, making this genomic feature unique in an evolutionary context as well as in pathogenicity.ImportanceAmphibian populations are declining worldwide at an unprecedented rate. Although various factors are thought to contribute to this phenomenon, chytridiomycosis has been identified as one of the leading causes. This deadly fungal disease is cause by Batrachochytrium dendrobatidis, a chytrid fungus species unique in its pathogenicity and, furthermore, its specificity to amphibians. Despite more than two decades of research, the biology of this fungus species and its deadly interaction with amphibians had been notoriously difficult to unravel. Due to the alarming rate of worldwide spread and associated decline in amphibian populations, it is imperative to incorporate novel genomic and genetic techniques into the study of this species. In this study, we present the first reported potential pathogenicity factors in B. dendrobatidis. In silico studies such as this allow us to identify putative targets for more specific molecular analyses, furthering our hope for the control of this pathogen.

Dataset Information

Global gene expression profiles for life stages of the deadly amphibian pathogen Batrachochytrium dendrobatidis.

Publications

Global gene expression profiles for life stages of the deadly amphibian pathogen Batrachochytrium dendrobatidis.

Similar Datasets

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