The effect of <i>XRN1</i> evolution on the restriction of the L-A and killer viruses of <i>S</i>. <i>cerevisiae</i>.

<p>(A) (<i>Top row</i>) dsRNA extraction from <i>S</i>. <i>cerevisiae xrn1</i>Δ with or without complementation by <i>XRN1</i> from different species of <i>Saccharomyces</i> (<i>S</i>. <i>cer—S</i>. <i>cerevisiae</i>; <i>S</i>. <i>mik—S</i>. <i>mikatae</i>; <i>S</i>. <i>kud—S</i>. <i>kudriavzevii; S</i>. <i>bay—S</i>. <i>bayanus</i>). From the same agarose gel, the first two lanes were spliced to the last three lanes for clarity. (<i>Bottom two rows</i>) Western blots showing the expression of HA-tagged Xrn1p and Adh1p (control) within each complemented strain. (B) (<i>Top</i>) Domain diagrams of Xrn1p showing the position of the catalytic residue E176 and the location of the C-terminal truncations of Xrn1p (dashed line). Xrn1p with the E176G mutation or the Δ1206–1528 truncation are catalytically inactive, as described previously [<a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1005890#ppat.1005890.ref049" target="_blank">49</a>]. (<i>Bottom</i>) dsRNA extraction from <i>S</i>. <i>cerevisiae xrn1</i>Δ expressing wild type <i>XRN1</i>, the catalytically inactive <i>XRN1</i>(E176G) or truncation mutants of Xrn1p (all derived from <i>S</i>. <i>cerevisiae</i>). (C) A representative picture of <i>S</i>. <i>cerevisiae</i> killer (L-A⁺ Killer⁺) and non-killer (L-A^- Killer^-) yeasts and the effect of killer toxin expression on the growth of a lawn of sensitive yeast. (D) The effect of Xrn1p expression on the diameter of the kill zones around killer yeast. Asterisks are indicative of a significant difference in mean kill zone area compared to all other samples tested (Tukey-Kramer test p<0.05). See <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1005890#ppat.1005890.s002" target="_blank">S2 Fig</a> for representative images of the kill zones.