Amino acid–level differences in alpha-tubulin sequences are uniquely required for meiosis

Members of the tubulin gene family members are essential components of the cytoskeleton; however, functional diversity of tubulin isoforms is poorly understood. Here, we addressed this question using <i>Schizosaccharomyces pombe</i> as a model system. These yeast encode two α-tubulins, <i>nda2</i> and <i>atb2</i>, that are very similar at the amino acid level but differ in their roles in organism's survival: <i>nda2</i> deletion is lethal, while lack of <i>atb2</i> does not interfere with cell viability. Using CRISPR-Cas9 gene editing, we generated a yeast strain expressing <i>atb2</i> amino acid sequence utilizing <i>nda2</i> codon usage in the native <i>nda2</i> locus. Such <i>nda2</i>-coded <i>atb2</i> (NCA) yeast, unlike <i>nda2</i> knockout, were viable and displayed no visible abnormalities in vegetative life cycle. Instead, they displayed strong impairments in sporulation and meiosis, linked to altered balance of several spindle proteins. Our data indicate that <i>nda2</i> protein is uniquely required for normal meiosis, and identify novel protein- and nucleotide-level determinants driving functional distinction between closely related tubulin isoforms.