This project will investigate the mechanisms by which pathogens evolve new host ranges; despite the direct relevance of host-range evolution to wildlife disease, agriculture, and human health, these mechanisms are still poorly understood. The common, ecologically important and widely studied insect-pathogenic fungus Metarhizium is an ideal model for studying the evolution of pathogens, pathogenesis and infectious disease. Closely related strains of these fungi have independently evolved as either broad-spectrum generalists (infecting a broad range of insects) or as specialists with narrow, specific host ranges (with particular strains infecting only locusts, grasshoppers, scarab beetles, or other particular insect groups). Some of the generalist insect pathogens also form beneficial associations with plant roots. Atlases of genomic diversity and gene expression will be assembled for four generalist and seven specialist Metarhizium strains, and coupled with bioinformatic analysis and hypothesis-driven experiments on select candidate genes, to determine: 1) the number, nature and networking of genes that regulate and execute infection processes; 2) the factors controlling virulence, host-range specificity and host-switching; 3) key targets for engineering alterations of pathogen performance for environmentally benign management of insect pests, and 4) development of a tractable model for studying mutation rates over evolutionary time. The focus of this research on the genetic basis of transitions between specialist and generalist host ranges will provide a much-needed model for understanding the evolution of new diseases. Finally, this project is excellent for research training as it exposes students to genomics, bioinformatics, molecular biology, microbiology, microscopy and fundamental scientific principles of host-pathogen biology and evolution. In addition to training a postdoctoral associate and two graduate students, this study will provide research opportunities for undergraduate students, including six from underrepresented groups; research activities will also be used to develop lesson plans for various classroom projects.
