Fig. 1.

NUM1 is essential in fzo1 dnm1 cells. (A) Heterozygous Δfzo1 Δdnm1 Δnum1 diploid cells were sporulated, and spores from individual tetrads were arranged in a column on YPD medium. Growth on selective plates was used to score the deletion marker and determine the genotypes of haploid cells, which are indicated. (B) Construction of a temperature-sensitive fzo1 dnm1 num1 strain using fzo1-1. Serial dilutions of the indicated strains were plated on YPD medium and grown at the permissive (23 °C) or nonpermissive (37 °C) temperature. (C) The morphology of mitochondria in the indicated strains expressing mito-dsRED was analyzed by fluorescence microscopy. Wild-type, Δdnm1, Δnum1, and Δdnm1Δnum1 cells were grown at 30 °C before imaging, and fzo1-1 and fzo1-1 Δnum1 cells were imaged after the cells were shifted to the nonpermissive temperature (37 °C) for 5 h. (D) The distribution of mitochondria in the indicated cells expressing mito-dsRED was analyzed by fluorescence microscopy before and after a temperature shift from 23 °C to 37 °C for 5 h. Cells were stained with calcofluor to image septa and bud scars to distinguish mother (marked with an “M”) and daughter cells. Whole-cell projections of cells imaged after the temperature shift to 37 °C are shown. Data are shown as the mean ± SE of three independent experiments, in each of which >75 cells were counted. (Scale bars, 2 μm.)