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. 2020 Oct 16;9:e62337. doi: 10.7554/eLife.62337

Figure 2. Plasmid instability is a heritable trait in three natural S. cerevisiae isolates.

(A) A colony sectoring assay qualitatively measures GFP-2μ reporter plasmid loss on solid media. Whereas the majority of colonies in the BY4742 background express GFP, only a small fraction of cells in colonies from wild isolates Y9, Y12, and YPS1009 express GFP. (B) The MCM assay quantifies the frequency of 2μ loss events in different yeast strains. Haploid cells from three wild isolates (Y9, Y12, YPS1009) have significantly lower plasmid retention than haploid cells from the laboratory BY4742 strain. ***p<0.0001, Kruskal-Wallis test. (C) SCAMPR assays confirm that a significantly smaller fraction of Y9 strain haploid cells retain the GFP-2μ reporter plasmid after 24 hr, relative to haploid BY4742 cells. ***p<0.0001, Kruskal-Wallis test.

Figure 2.

Figure 2—figure supplement 1. Three natural S. cerevisiae isolates lack endogenous 2μ plasmids.

Figure 2—figure supplement 1.

(A) Representative PCR analysis shows that most of the 52 natural isolates tested harbor endogenous 2μ plasmids, except for three strains (one indicated). Drosophila melanogaster DNA was included as a negative control template. Representative gel shown for the presence of REP1 (Materials and methods) (B) Southern blot analysis confirms the absence of endogenous 2μ plasmids in the three natural isolates Y9, Y12, and YPS1009 as compared to the BY4742 positive control.
Figure 2—figure supplement 2. BY4742 and Y9 show similar growth rates.

Figure 2—figure supplement 2.

BY4742 and haploid Y9 show similar growth dynamics in defined liquid media, both without the GFP-2μ reporter plasmid (blue triangle and red circle respectively), or with the reporter plasmid in the presence of G418 selection (black square and black triangle respectively).