Figure 1.

Complementary temperature shift experiment. For details see MATERIALS AND METHODS. (A) In the first experiment top2 and wild-type (wt) cells were shifted to meiotic conditions and incubated at restrictive temperature. At hourly intervals aliquots were removed and shifted to permissive temperature. (B) In the second experiment, after shift to meiotic conditions, cells were incubated at permissive temperature, and every hour an aliquot was removed and shifted to restrictive temperature. (C) The percentage of horse tail nuclei for the experiment presented in A is shown for wild type. Data about horse tail nuclei in top2 could not be included, because the high abundance of mitotic cells with an elongated nucleus caused by the cut phenotype made an objective estimation impossible. (D) Data about horse tail nuclei in top2 as well as in wild type for the experiment presented in B are shown. In this experiment the first meiotic division was delayed in the top2 strain compared with wild type at permissive temperature. The top2 mutation has a slow growth phenotype at permissive temperature, probably because the cells have a problem with the mitotic division. The same problem probably delayed meiosis I in the top2 mutant at permissive temperature. Spor., sporulation efficiency; >1 nucl., percentage of cells that performed the first meiotic division.