Figure 6. Alleles on all three Sk chromosomes show drive (independent of mitochondrial DNA type).

(A) Sk alleles were inherited by significantly more than 50% of the viable spores produced by Sk/Sp hybrids, except ura1 and ura4 (G-test p<0.01; n >100 for each). The markers nearest to the meiotic drive loci (i.e., those showing the greatest bias towards Sk inheritance) are shown in boldface. The color scheme is the same as that in Figure 4. The data underlying these numbers are shown in Figure 4—figure supplement 3, and Figure 6—figure supplement 1. (B) The Sk alleles of lys1, his5 and ade6 show significant drive both in the presence and absence of recombination (**p<0.01, n >300 for lys1 and his5, n >80 for ade6). The amount of his5 drive is greater in the absence to Rec12 due to enhanced linkage with the driving locus. The data underlying this graph are shown in Figure 6—figure supplement 1. (C) Incompatibilities between the Sk mitochondrial DNA and Sp nuclear genes are not responsible for the drive phenotype because we observed the same drive in rec12Δ Sk/Sp hybrids with either Sk or Sp-derived mitochondrial DNA (**p<0.01, n >200 for lys1 and his5, n >50 for ade6). The data underlying this graph are shown in Figure 6—figure supplement 4.

DOI: http://dx.doi.org/10.7554/eLife.02630.024

Figure 6—figure supplement 1. Summary of Sk/Sp hybrid and pure species diploid meiotic phenotypes and distribution of alleles in their progeny.

We induced Sk/Sp hybrids as well as Sk/Sk and Sp/Sp control diploids to undergo meiosis and measured their fertility using a viable spore yield assay (VSY). All diploids were heterozygous for genetic markers on chromosome 1 (lys1), chromsome 2 (his5) and chromsome 3 (ade6). We genotyped the viable spores from each diploid using these markers. In the rec12⁺ Sk/Sp hybrids, the Sk parent contributed the his5⁺, lys1⁻, and ade6⁻ alleles. In cases where the diploids had co-dominant markers on chromosomes 2 and 3, we were also able to determine the number of chromosome 3 aneuploids and diploids amongst the viable spores. Parts of these data are also presented in Figure 1H, Figure 3, Figure 5, Figure 6, Figure 8, and Figure 8—figure supplement 2.

DOI: http://dx.doi.org/10.7554/eLife.02630.025

Figure 6—figure supplement 2. Biased transmission favoring Sk alleles on chromosomes 1 and 2 is observed in aneuploid and haploid spores.

The Sk/Sp rec12⁺ data presented in Figure 6B and Figure 6—figure supplement 1 were sorted to display aneuploid and haploid spores seperately. The diploid was heterozygous for genetic markers on chromosome 1 (lys1), chromsome 2 (his5) and chromsome 3 (ade6). We genotyped the viable spores of each diploid using these markers. The Sk parent contributed the his5⁺ and lys1⁻ alleles.

DOI: http://dx.doi.org/10.7554/eLife.02630.026

Figure 6—figure supplement 3. Distribution of progeny from rec12Δ Sk/Sp hybrid meiosis.

rec12Δ Sk/Sp hybrid diploids were sporulated and we genotyped the viable spores using genetic markers that distinguished each chromosome (n = 589). Chromosomes 2 and 3 contained codominant markers, which allowed us to definitively determine which strains had two copies of these chromosomes. We assumed that all strains that inherited two copies of chromosome 2 and chromosme 3 were diploids, because chromosome 1 aneuploids are inviable in Sp (Niwa et al., 2006). We assume the same is likely true in Sk and Sk/Sp hybrids because we very rarely recover marker combinations consistent with aneuploidy for chromosomes 1 or 2 from rec12Δ crosses. We assume that the few such progeny we do recover are rare recombinants (Davis and Smith, 2003). The plot shows the distribution of the viable spores that inherited each chromosome. Sp chromosomes are designated P1-P3, Sk chromosomes are designated K1-K3. This analysis is limited in that it assumes no recombination. However, recombination does occur at a low frequency (Davis and Smith, 2003). For example, all strains tested that have P2 K3 or K2 P3 (incompatible combinations) were recombinant.

DOI: http://dx.doi.org/10.7554/eLife.02630.027

Figure 6—figure supplement 4. Meiotic drive in Sk/Sp hybrids is independent of mitochondrial DNA.

We induced Sk/Sp hybrids heterozygous for genetic markers on chromosome 1 (lys1), chromosome 2 (his5) and chromosome 3 (ade6) containing either Sk or Sp mitochondrial (mt) DNA to undergo meiosis. We genotyped the viable spores using these markers and indicated the number that inherited each allele. The Sk parent contributed the his5⁻, lys1⁺, and ade6⁻ alleles.

DOI: http://dx.doi.org/10.7554/eLife.02630.028