Representative lifetime history plots of astral microtubules in HU-arrested, mock-treated, and epothilone-treated cells. Epothilone treatment significantly stabilizes microtubules in WT, Tub1-only, and Tub3-only cells. Two microtubules are shown for each of the indicated cell types in untreated (left), mock (DMSO; middle), and 10 µM epothilone B treatment (EpoB; right). Tub1-only cells contain the TUB1 ORF in both the TUB1 and TUB3 loci, while Tub3-only cells harbor the TUB3 ORF in both. Microtubules in Tub1-only and Tub3-only cells were visualized with an exogenous copy of GFP-Tub1 and GFP-Tub3, respectively. WT-Tub1 and WT-Tub3 are WT cells harboring an exogenous copy GFP-Tub1 and GFP-Tub3, respectively. MT, microtubule.