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. Here, we develop a method for detecting telomeric sequences in Saccharomyces cerevisiae genomes from raw Oxford Nanopore Technologies (ONT) sequencing reads, providing a comprehensive view of TL distributions both genome-wide and at individual chromosome extremities. We analyze the TL distribution in 100 S. cerevisiae strains, representing the genetic and ecological diversity of the species. Our analysis reveals a large diversity in TL distributions within the species, largely driven by interextremity differences, ploidy level, and subtelomere structure. Polyploid strains display significantly longer telomeres than diploid and haploid strains, and experiments with artificially generated polyploids in two independent genetic backgrounds confirm that higher ploidy levels lead to telomere elongation. Furthermore, we find that the subtelomeric Y' element exerts two distinct and opposing effects: (1) the presence of Y' elements at a chromosome extremity is associated with shorter telomeres in cis, but (2) the overall Y' element content in a strain correlates with longer telomeres. Finally, we show that the length of the shortest telomeres remains relatively constant across strains, suggesting a selective constraint at the species level. This study reveals the diversity of TL in S. cerevisiae and highlights key factors shaping TL distributions both genome-wide and at individual chromosome extremities.