Kip3 suppresses spindle microtubule dynamics and limits midzone length during anaphase. (a and b) Late anaphase spindles in control (a) and kip3Δ (b) cells expressing GFP-tubulin (top) were imaged over time to generate kymographs (bottom). In control and kip3Δ cells, microtubules polymerizing out from the spindle poles toward the midzone were observed as diagonal regions of increased fluorescence (arrowhead). In kip3Δ cells, polymerization events were observed extending out of the midzone toward the spindle poles (arrow). (c) Percentage of spindles that displayed microtubule polymerization >1 µm from the midzone toward the spindle pole. For control and kip3Δ cells, n = 41 and 48, respectively. (d) Magnitude of the longest polymerization event for each spindle scored in panel c, P < 0.05. (e) Fluorescence images of Ase1-3YFP localization on late anaphase spindles (CFP-tubulin). (f) Length of Ase1-3YFP region after 1 h anaphase arrest. Average ± SE, P < 0.005, n = 90 from three experiments for each cell type. Bars: (horizontal) 2 µm; (vertical) 120 s.