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The making of tree pathogens: big data approach

Richard Hamelin: University of British Columbia

<div>Tree pathogens are responsible for some of the most devastating outbreaks in forests. In spite of their importance, we know relatively little about their origin and sources, and their basic common characteristics. A fundamental question in forest pathology is what makes a tree pathogen? Pathogenic species are often phylogenetically related to non-pathogenic species, which provides an opportunity to identify the determinants of pathogenicity. By harnessing the power of genomics we can compare fungi with a broad range of life-style, host specificity and pathogenicity. The Pathobiome and BioSAFE projects involve sequencing and comparing the genomes of multiple pathogens of trees to identify common and unique genomic determinants that can be developed into tools for monitoring and risk prediction. The genome of the wood-infecting poplar canker pathogen <em>Sphaerulina</em><em> musiva</em> was compared to the genome of a close relative that lacks that ability (i.e. <em>S. populicola</em>). <em>Sphaerulina</em><em> musiva</em> has acquired and expresses a gene arsenal, such as hemicellulose-degrading enzymes, peptidases, and metabolite transporters that are required for colonization of woody tissues. A secondary gene cluster that is activated upon interaction with the host and several carbohydrate degradation genes have the signature of horizontal transfer from both ascomycete fungi associated with wood decay and prokaryotes. These results suggest that a dynamic genome landscape can drive pathogenic potential.</div>