Fig. 1.

The genomic organization of the mating-type region in wild strains and world-wide diversity of switchers and non-switchers. a Schematic of the genetic arrangement for switcher (h⁹⁰; middle) and the two most common non-switcher phenotypes (h^–S and h^+N; top and bottom, respectively). Regions are not to scale. The switcher’s active mating-type locus mat1 (red box) switches between Plus (P) and Minus (M), using the silent cassettes as templates during cell division. The non-switcher strain h^–S contains only the minus cassette, due to deletion of part of the silent region. The non-switcher strain h^+N is the result of a duplication of almost the entire silent mating type and only expresses the P cassette at mat1 (see ref. ⁹). b The unrooted maximum-likelihood tree for 57 natural fission yeast isolates, based on the L region (results for the 3ʹ and 5ʹ flanking region of entire mating-type region in Supplementary Fig. 3), results in two main clades (indicated by brackets). Branch values show bootstrap support when >50. Colour codes indicate switching phenotypes based on (i) previous observations³⁵, (ii) our test of single-cell colony mating (mating observations) or (iii) the prediction from inferred genotype. Genotypes were predicted based on the coverage and paired-read analyses, as shown in the last two columns (only shown when differing from the h⁹⁰ haplotype). When genotypes differ from the standard configurations (a), additional information on predicted number of copies for the L- and K-region, and P- and M-cassette (Supplementary Fig. 1) is presented between brackets. The samples that do not fit any existing genotypes in b are labelled as ‘other’