Diverse modes of chromosome terminal deletion in spontaneous canavanine-resistant mutants.

Canavanine resistance has been used to analyze mutation rates in the fission yeast . However, the genetic basis of canavanine resistance in this organism remains incompletely understood. Here, we performed whole genome sequencing on five spontaneously arising canavanine-resistant mutants, including the mutant isolated in the 1970s. This analysis revealed that three mutants, including , experienced terminal deletions of the left arm of chromosome II, leading to the loss of multiple amino acid transporter genes. Interestingly, these three mutants underwent chromosome terminal deletion through distinct mechanisms, including homology-driven translocation, homology-independent chromosome fusion, and de novo telomere addition. Our findings shed new light on the genetic basis of canavanine resistance and mechanisms underlying chromosome terminal deletions in fission yeast.