title: Evaluating the within-host fitness effects of mutations fixed during virus adaptation to different ecotypes of a new host.
abstract: The existence of genetic variation for resistance in host populations is assumed to be essential to the spread of an emerging virus. Models predict that the rate of spread slows down with the increasing frequency and higher diversity of resistance alleles in the host population. We have been using the experimental pathosystem Arabidopsis thaliana-tobacco etch potyvirus (TEV) to explore the interplay between genetic variation in host's susceptibility and virus diversity. We have recently shown that TEV populations evolving in A. thaliana ecotypes that differ in susceptibility to infection gained within-host fitness, virulence and infectivity in a manner compatible with a gene-for-gene model of host-parasite interactions: hard-to-infect ecotypes were infected by generalist viruses, whereas easy-to-infect ecotypes were infected by every virus. We characterized the genomes of the evolved viruses and found cases of host-driven convergent mutations. To gain further insights in the mechanistic basis of this gene-for-gene model, we have generated all viral mutations individually as well as in specific combinations and tested their within-host fitness effects across ecotypes. Most of these mutations were deleterious or neutral in their local ecotype and only a very reduced number had a host-specific beneficial effect. We conclude that most of the mutations fixed during the evolution experiment were so by drift or by selective sweeps along with the selected driver mutation. In addition, we evaluated the ruggedness of the underlying adaptive fitness landscape and found that mutational effects were mostly multiplicative, with few cases of significant epistasis.
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-UPV, València 46022, Spain.
authors.forename: Julia
authors.initials: J
authors.lastname: Hillung
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-UPV, València 46022, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Cuevas
authors.affiliation: Instituto de Biología Molecular y Celular de Plantas, Consejo Superior de Investigaciones Científicas-UPV, València 46022, Spain The Santa Fe Institute, Santa Fe, NM 87501, USA santiago.elena@csic.es.
authors.forename: Santiago F
authors.identifier: http://orcid.org/0000-0001-8249-5593
authors.initials: SF
authors.lastname: Elena
mesh_terms: D000222:Adaptation, Physiological; D017360:Arabidopsis / Q000145:classification / Q000235:genetics* / Q000821:virology*; D019020:Directed Molecular Evolution; D005814:Genes, Viral; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D058507:Host Specificity; D054884:Host-Pathogen Interactions / Q000235:genetics* / Q000502:physiology; D008957:Models, Genetic; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010935:Plant Diseases / Q000235:genetics / Q000821:virology; D017800:Potyvirus / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology; D012367:RNA, Viral / Q000235:genetics
chemical_list: D012367:RNA, Viral
keywords: adaptive mutations; epistasis; experimental evolution; host-range expansion; virus evolution; virus–plant interaction