Presence of non-supressive, M2-related dsRNAs molecules in Saccharomyces cerevisiae strains isolated from spontaneous fermentations

Total dsRNA extractions in five killer K2 strains of Saccharomyces cerevisi ae isolated from spontaneous fermentations revealed the presence of a novel dsRNA fragment (which we named NS dsRNA) of approximately 1.30 kb, togethe r with L and M2 dsRNAs. NS dsRNA appeared to be encapsidated in the same ki nd of viral particles as L and M2 dsRNA. Northern blot hybridization experi ments indicated that NS dsRNA was derived from M2 dsRNA, likely by deletion of the internal A + U-rich region. However, unlike S dsRNAs (suppressive f orms derived from M1 dsRNA in K1 killers), NS dsRNA did not induce exclusio n of the parental M2 dsRNA when the host strain was maintained for up to 18 0 generations of growth. (C) 1999 Federation of European Microbiological So cieties. Published by Elsevier Science B.V. All rights reserved.