Visualization of the effect of TUB3-E255A on microtubules after GAL1-shutoff of ectopic TUB1 expression. (A) Experimental scheme. Strain DBY9576, containing the lethal allele TUB3-E255A, is viable in galactose medium because suppressing quantities of wild-type TUB1 are expressed from the GAL1 promoter. When placed in glucose medium, transcription of the GAL1p-TUB1 copy is repressed, and the cells become inviable. A copy of GFP::TUB1 allows visualization of the microtubules. Strain DBY9574, which contains TUB3, serves as a control. (B) Microtubules in TUB3 and TUB3-E255A strains after 8 h of glucose repression of GAL1-driven TUB1. Time-lapse series showing the dynamics of the representative microtubules MT1 and MT2 are contained in the videos 9B_MT1.mov and 9B_MT2.mov. Microtubule lengths are plotted over time. Open circles indicate microtubules in the focal plane, and filled circles indicate a microtubule partially out of the focal plane. For MT2 plot, dotted line connects in-focus data points. Arrows indicate anaphase spindles with poles brighter than along length, and arrowhead indicates unattached microtubule. Bar, 3 μm.