Distinct requirements for α- and β-tubulin gene copy number in microtubule function. (A) Current model for how cells build microtubules from tubulin genes through folding and assembly of polymerization competent heterodimers. (B) Representative growth curves for wild-type and TUB1/tub1Δ heterozygous cells. All cultures were grown at 30°C with agitation for 24 h, and OD600 was measured every 5 min. Lines are mean of six technical replicates, and shading represents the 95% CI. (C) Doubling times of indicated heterozygous tubulin mutants normalized to wild-type controls. For each genotype, at least four technical replicates of two biological replicates were utilized across at least three independent experiments. Circles represent cultures in separate wells, and triangles are the means of each day. Colors indicate independent experiments. P value between wild type and mutant based on t test after one-way ANOVA with a Tukey post-hoc test. Bars are mean ±95% CI. (D) 10-fold dilution series of indicated strains were spotted onto rich media or rich media supplemented with benomyl. Cells were grown at the indicated temperature for the indicated number of days. (E) Representative image of a wild-type pre-anaphase cell expressing Spc110-mNeonGreen. Red line indicates distance between two poles. Scale bar = 1 µm. Image is a maximum intensity projection of z series. (F) Mean pre-anaphase spindle length per cell across 5-min imaging timeframe. For each genotype, two biological replicates were used across two independent experiments. Each dot represents the mean from one cell. Colors indicate independent experiments. P value between wild type and mutant based on t test after one-way ANOVA. Bars are mean ± 95% CI. (G) Coefficient of variance of pre-anaphase spindle length per cell across 5-min imaging timeframe from the dataset used in F. Each dot represents the mean from one cell. Colors indicate independent experiments. P value between wild type and mutant based on t test after one-way ANOVA. Bars are mean ±95% CI.