Parallels between mutualism and pathogenesis: A comparison of lichen and pathogenic symbioses
E. M. MEDINA (1), O. Mueller (1), D. Armaleo (1), F. Lutzoni (1). (1) Duke University, Durham, NC, U.S.A.
Symbiotic interactions involving fungi are ubiquitous and form a continuum from mutualism to parasitism. The two ends of this spectrum were thought to generate disparate evolutionary patterns, but current understanding of these symbioses suggests that both interactions coincide in many mechanisms (such as defense and infection) and genomic signatures. Additionally, there is an ongoing debate on evolutionary signatures of these interactions (i.e., “arms race” versus “mutualistic environment”). The lichen symbiosis has been mostly absent from this debate because of the lack of knowledge about the genes at play in establishing and maintaining this type of symbiosis. Here we use nine lichen mycobiont genomes encompassing Lecanoromycetes, Lichinomycetes, Eurotiomycetes and Arthoniomycetes, to explore the genomic signatures of symbiosis and compare these patterns with more than 30 Pezizomycotina genomes encompassing pathogenic (on animals and plants), non-pathogenic, and beneficial interactions. Specifically, we compare patterns of repetitive sequences and transposable elements as potential mechanisms to promote adaptation, as well as gene density and evolutionary rates as putative hallmarks of symbiosis. Complementarily, we use congruence of mechanisms between beneficial and parasitic interactions as a proxy to predict genes of importance in mycobiont-photobiont interactions using key genes in host-pathogen interactions.
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