Natural diversity of telomere length distributions across 100 Saccharomyces cerevisiae strains
Telomeres gradually shorten at each cell division and telomerase counteracts this shortening by elongating telomere sequences. This dynamic balance between elongation and shortening results in a steady-state telomere length (TL) distribution. We developed a method for detecting telomeric sequences in Saccharomyces cerevisiae genomes from raw Oxford Nanopore Technologies (ONT) sequencing reads, and provide a complete view of the global TL distribution in a strain as well as chromosome-extremity-specific TL distributions. Here, we analyzed the TL distribution in 100 S. cerevisiae strains, which represented the genetic and ecological diversity of the species. Our analysis revealed a large diversity in TL distributions within the species, largely driven by inter-extremity differences, ploidy level, and subtelomere structure. Indeed, we observed significantly longer telomeres in polyploids compared to diploids and haploids in the dataset, and by generating artificial polyploids in two independent isogenic backgrounds, we demonstrated that increased ploidy induces telomeres to become longer. Furthermore, we found that the subtelomeric Y' element exerts two distinct and opposing effects: (i) the presence of Y' elements at a chromosome extremity is associated with shorter telomeres in cis, but (ii) the overall Y' element content in a strain correlates with longer telomeres. Interestingly, the length of the shortest telomeres remained relatively constant across strains, suggesting a selective constraint at the species level. This study reveals the TL diversity in S. cerevisiae and highlights key factors shaping TL distributions both globally and at individual chromosome extremities.