title: A population study of killer viruses reveals different evolutionary histories of two closely related Saccharomyces sensu stricto yeasts.
abstract: Microbes have evolved ways of interference competition to gain advantage over their ecological competitors. The use of secreted killer toxins by yeast cells through acquiring double-stranded RNA viruses is one such prominent example. Although the killer behaviour has been well studied in laboratory yeast strains, our knowledge regarding how killer viruses are spread and maintained in nature and how yeast cells co-evolve with viruses remains limited. We investigated these issues using a panel of 81 yeast populations belonging to three Saccharomyces sensu stricto species isolated from diverse ecological niches and geographic locations. We found that killer strains are rare among all three species. In contrast, killer toxin resistance is widespread in Saccharomyces paradoxus populations, but not in Saccharomyces cerevisiae or Saccharomyces eubayanus populations. Genetic analyses revealed that toxin resistance in S. paradoxus is often caused by dominant alleles that have independently evolved in different populations. Molecular typing identified one M28 and two types of M1 killer viruses in those killer strains. We further showed that killer viruses of the same type could lead to distinct killer phenotypes under different host backgrounds, suggesting co-evolution between the viruses and hosts in different populations. Taken together, our data suggest that killer viruses vary in their evolutionary histories even within closely related yeast species.
authors.affiliation: Genomics Research Center, Academia Sinica, 128 Sec. 2, Academia Road, Nankang, Taipei, 115, Taiwan.
authors.forename: Shang-Lin
authors.initials: SL
authors.lastname: Chang
authors.affiliation: Institute of Molecular Biology, Academia Sinica, 128 Sec. 2, Academia Road, Taipei, 115, Taiwan.
authors.forename: Jun-Yi
authors.initials: JY
authors.lastname: Leu
authors.affiliation: Genomics Research Center, Academia Sinica, 128 Sec. 2, Academia Road, Nankang, Taipei, 115, Taiwan.
authors.forename: Tien-Hsien
authors.identifier: http://orcid.org/0000-0002-1747-4478
authors.initials: TH
authors.lastname: Chang
mesh_terms: D005075:Biological Evolution; D055646:Killer Factors, Yeast / Q000737:chemistry*; D008969:Molecular Sequence Data; D010641:Phenotype; D012328:RNA Viruses / Q000502:physiology*; D012440:Saccharomyces / Q000235:genetics* / Q000821:virology*; D017422:Sequence Analysis, DNA
chemical_list: D055646:Killer Factors, Yeast
keywords: interference competition; toxin resistance; virus-host co-evolution; yeast killer virus