Fig. 2. A decrease in Mob2p level leads to a defect in activation of bipolar growth. (A) Wild-type (YDM105) (a) and mob2 shut-off cells (YDM1032) (b) were grown to exponential phase at 30°C, then grown in the presence of 5 µg/ml thiamine for 15 hours and stained with Calcofluor. Areas of previous cell division (birth scars) were marked as dark bands (a,b; arrowheads). Note that in b, these cells did not grow at their new ends causing the new ends (arrowheads) not to be visible. New end growth was measured in YDM105 (c) and YDM1032 (d) strains with septa as the distance between the most recent birth scar and the cell end (see brackets). Fifty cells were analyzed in each strain. (B) cdc25-22 (YDM151) and cdc25 mob2::ura4+[pREP3X-mob2] (YDM1456) (16 hours +thiamine) were grown to exponential phase at 25°C, then grown for 12 hours in the presence of thiamine prior to shift to 36°C for 4 hours. In addition, mob2::ura4+[pREP3X-mob2] (YDM1456) cells were grown in the absence of thiamine at 25°C, then shifted to 36°C for 4 hours (0 hour +thiamine). Cells were fixed with 4% paraformaldhyde, stained with Calcofluor and scored with monopolar or bipolar growth. The result shown in a was obtained from two independent experiments. The corresponding Calcofluor-stained images are shown in (b) YDM151, (c) YDM1456 (0 hour + thiamine) and (d) YDM1456 (16 hours + thiamine). Arrowheads in d indicate the cells with monopolar growth.

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