COLLABORATIVE RESEARCH: GENOMIC DETERMINANTS OF PATHOGENICITY AND SUSCEPTIBILITY IN AN EMERGING FUNGAL PATHOGEN AND ITS VERTEBRATE HOSTS

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Amphibians around the world are disappearing at an alarming rate. Many recent declines have been caused by a deadly chytrid fungus called Batrachochytrium dendrobatidis (Bd). Bd has recently spread around the world and infects hundreds of amphibian species. This project focuses on understanding the interaction between the Bd pathogen and its amphibian hosts. Specifically the investigators will learn 1) why some amphibian species are devastated by Bd while others are not harmed and 2) why some strains of Bd are more deadly than others. The investigators will conduct an integrative and worldwide study of numerous Bd isolates and a diversity of frog species. Results from this project will help guide conservation efforts be targeted to the most vulnerable species and to areas where Bd will have the most devastating impact. Further the general understanding of host-pathogen interactions resulting from this project can be applied to other systems where wildlife are threatened with new emerging diseases. The project also provides training opportunities for undergraduate and graduate students, with a focus on broadening participation of underrepresented groups. In addition to scientific research, the project will provides education about biodiversity and conservation to the public and local public elementary school children through popular press publications, museum exhibits, and an outreach event called "Save the Frogs Day". The researchers in this project have taken genetic, genomic, immunological, and organismal approaches to accomplish their objectives. First, they will use a comparative approach to identify genomic variations in 60 Bd isolates gathered from around the world that vary in infectivity towards various amphibian hosts. Second, they will study variations in in vitro growth phenotypes that they propose directly relate to infectivity. Last, they will examine in vivo and cell culture-based phenotypes, in parallel with host tissue profiling. A key aspect of the third goal is that the applicants have selected 6 congeneric amphibian host pairs (2 species in each of three different genera) that vary in susceptibility to Bd. They will utilize Illumina-based sequencing techniques to obtain genome-wide association studies of the phenotypes of interest. In vivo infection phenotypes such as Bd burden under the common garden conditions tested will be coupled with transcriptomic analysis of host gene expression to evaluate differential responses by susceptible/tolerant hosts. To address this important problem, the investigators have blended evolutionary, ecological and physiological perspectives and this integrative approach promises to bring new insight into this field.