Abstract
Shorter centromeres have fewer kinetochore microtubules (kMTs) bound as evident in Saccharomyces cerevisiae where each chromosome is associated with a single kMT. Cells can also be conditioned in recruiting excess kMTs highlighting the flexibility of the kinetochore as the kMT binding interface. Here, we addressed the evolutionary significance of the inherent flexibility in conditionally recruiting excess kMTs. We identified a conserved arginine residue at the C- terminus of an essential outer kinetochore protein Dad2 that remained positively selected for ∼700 million years in fungi. While the conserved R126 residue in Dad2 is essential for viability in S. cerevisiae harboring short point centromeres, the corresponding arginine residues are functionally important but no longer essential for viability in either Candida albicans or Cryptococcus neoformans, each possessing longer regional centromeres. We revealed a gradual decline in the requirement of the conserved arginine for chromosome biorientation and mitotic progression with increasing centromere length. Finally, our results suggested that the mutational tolerance in organisms with regional centromeres is imparted by higher kinetochore protein levels known to recruit multiple kMTs per chromosome.
Competing Interest Statement
The authors have declared no competing interest.