Extended Data Fig. 1: Fusion chromosome paths and characterization.
From: Karyotype engineering by chromosome fusion leads to reproductive isolation in yeast
a, PCR verification of fusion chromosomes. Two pairs of primers are used to verify the fusion of two chromosomes, here presenting the fusion of chromosomes I and III. Only with successful fusion would an amplicon show in fusion chromosome junction PCR. In addition, the centromere region PCR amplicon is shorter, owing to the deletion of a centromere. Marker: 2-log DNA marker. b, Circos diagrams for different values of n are shown in the upper panel, with 16 chromosomes laid out in circles in a clockwise manner. Each grey line connecting each pair of chromosomes represents a possible intertelomeric link. The dashed coloured lines represent the path we chose. (Open circle indicates the starting chromosome, arrows show direction of fusion chromosomes.) Each fusion chromosome is labelled in the same colour, providing detailed information on fusion chromosome paths. The underlined chromosome has the active centromere for the fusion chromosome. Unchanged chromosomes are not shown, but the number of unchanged chromosome is indicated after +, for example, +9 means nine unchanged chromosomes. Fusion chromosome lengths are shown below. Please note that the length of the rDNA array (normally 1–2 Mb)is omitted here. *Chromosome containing rDNA array. In addition, telomeric ends are clearly labelled with the original chromosomes; L/R stands for left/right telomere. Active centromeres are written on the right of each fusion chromosome diagram. When we deleted CEN15 and made 4 bp of mutations in gRNA sites in BY4741 to fuse chromosomes X and XV together, the fusion strain grew more slowly than the wild type. The growth defect could be due to altered expression of the gene neighbouring CEN15 (YOR001W; RRP6). For this reason, CEN15 was maintained in the remaining centromere. c, Fusion chromosome paths from n = 4 to n = 2. Red lettering indicates the chromosome that has an active centromere in the compound chromosome. d, Multiple strategies that we attempted to construct an n = 1 strain. We tried changing chromosome arm length (strategy 3), centromere position (strategy 2), and which telomeres remained (strategy 1 and 2). In strategy 2, we attempted both versions of n = 1 strains, keeping either CEN7 or CEN15 as the active centromere. In addition, we also attempted the strategy 1 in both SIR2+ and sir2Δ backgrounds.
