Fig. 8. Alp4 functions independently of but is related to the Mad2 pathway in spindle checkpoint control. (A) Multiple septation phenotypes of the alp4mad2 double mutant in the presence of TBZ. alp4-1891 (black), alp4mad2 (hatched) and mad2 (dotted) mutants were grown in rich medium at 26°C and synchronized with HU (10 mM). After 3 h incubation, HU was washed out and TBZ was added, and the culture was monitored for 4 h. The percentage of septating cells displaying multiple septa is shown. (B) Cell morphology in the presence of TBZ. Typical cell morphology stained with calcofluor is shown (top, alp4-1891; middle, alp4mad2; bottom, mad2). The bar indicates 10 µm. (C) Progression through mitosis of the double mutant at the restrictive temperature. alp4 single (squares) or alp4mad2 double (circles) mutants were blocked with HU for 3 h at 26°C and released into HU-free medium at 36°C. The percentages of abnormal mitotic cells (closed symbols) and anaphase B nuclei (open symbols) were counted.