RNA viruses, M satellites, chromosomal killer genes, and killer/nonkiller phenotypes in the 100-genomes S. cerevisiae strains

We characterized previously identified RNA viruses (L-A, L-BC, 20S, and 23S), L-A–dependent M satellites (M1, M2, M28, and Mlus), and M satellite–dependent killer phenotypes in the Saccharomyces cerevisiae 100-genomes genetic resource population. L-BC was present in all strains, albeit in 2 distinct levels, L-BC(hi) and L-BC(lo); the L-BC level is associated with the L-BC genotype. L-BC(hi), L-A, 20S, 23S, M1, M2, and Mlus (M28 was absent) were in fewer strains than the similarly inherited 2µ plasmid. Novel L-A–dependent phenotypes were identified. Ten M(+) strains exhibited M satellite–dependent killing (K(+)) of at least 1 of the naturally M(0) and cured M(0) derivatives of the 100-genomes strains; in these M(0) strains, sensitivities to K1(+), K2(+), and K28(+) strains varied. Finally, to complement our M satellite–encoded killer toxin analysis, we assembled the chromosomal KHS1 and KHR1 killer genes and used naturally M(0) and cured M(0) derivatives of the 100-genomes strains to assess and characterize the chromosomal killer phenotypes.