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. 2005 Nov;16(11):5410-7.
doi: 10.1091/mbc.e05-07-0678. Epub 2005 Aug 31.

Role of essential genes in mitochondrial morphogenesis in Saccharomyces cerevisiae

Katrin Altmann  1 , Benedikt Westermann
Affiliations

Role of essential genes in mitochondrial morphogenesis in Saccharomyces cerevisiae

Katrin Altmann et al. Mol Biol Cell. 2005 Nov.

Abstract

Mitochondria are essential organelles of eukaryotic cells. Inheritance and maintenance of mitochondrial structure depend on cytoskeleton-mediated organelle transport and continuous membrane fusion and fission events. However, in Saccharomyces cerevisiae most of the known components involved in these processes are encoded by genes that are not essential for viability. Here we asked which essential genes are required for mitochondrial distribution and morphology. To address this question, we performed a systematic screen of a yeast strain collection harboring essential genes under control of a regulatable promoter. This library contains 768 yeast mutants and covers approximately two thirds of all essential yeast genes. A total of 119 essential genes were found to be required for maintenance of mitochondrial morphology. Among these, genes were highly enriched that encode proteins involved in ergosterol biosynthesis, mitochondrial protein import, actin-dependent transport processes, vesicular trafficking, and ubiquitin/26S proteasome-dependent protein degradation. We conclude that these cellular pathways play an important role in mitochondrial morphogenesis and inheritance.

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Figures

Figure 1.
Figure 1.
Essential cellular processes required for maintenance of mitochondrial morphology. Promoter shutoff strains (n = 768) lacking essential gene products were screened for mutants with aberrant mitochondrial morphology. Of these strains, 15% showed strong defects in mitochondrial morphology and distribution (average, indicated by dotted line). Black columns indicate functional classes that contained a high percentage of mutants with disorganized mitochondria. In case of protein degradation factors, genes encoding proteasome subunits were counted separately (white column). Light gray columns represent genes of unknown function, and genes of known functions other than that included in the black columns. A complete list of screened yeast strains can be found in Supplementary Table 1.
Figure 2.
Figure 2.
Yeast cells lacking ergosterol biosynthetic enzymes harbor aberrant mitochondria. Strains expressing mitochondria-targeted GFP were grown in the absence (- Dox) or presence (+ Dox) of doxycycline in YPD medium to logarithmic growth phase and analyzed by fluorescence microscopy. Left, differential interference contrast (DIC) image; middle, mitochondrial morphology of a representative cell; right, merged image. WT, wild type. Bar, 5 μm.
Figure 3.
Figure 3.
Yeast cells lacking components of the mitochondrial protein import and sorting machinery harbor aberrant mitochondria. Yeast strains were analyzed as in Figure 2. Bar, 5 μm.
Figure 4
Figure 4
(facing page). Yeast cells lacking components linked to the actin cytoskeleton harbor aberrant mitochondria. Strains expressing mitochondria-targeted GFP were grown in the absence (- Dox) or presence (+ Dox) of doxycycline in YPD medium to logarithmic growth phase, fixed, stained with rhodamine phalloidin, and analyzed by fluorescence microscopy. First image, differential interference contrast (DIC) image; second image, mitochondrial morphology (mito); third image, organization of filamentous actin (a reversed fluorescence image is shown to better visualize faint actin cables); and fourth image, merged image of reversed actin fluorescence and mitochondrial fluorescence. On the right hand side, the mutant class is indicated: A, aberrant mitochondria and disorganized actin cytoskeleton; B, aberrant mitochondria and normal actin cytoskeleton; C, normal mitochondria and disorganized actin cytoskeleton; D, normal mitochondria and normal actin cytoskeleton. WT, wild type. Bar, 5 μm.
Figure 5.
Figure 5.
Yeast cells lacking components of the protein secretion and vesicular trafficking machinery harbor aberrant mitochondria. Yeast strains were analyzed as in Figure 2. Bar, 5 μm.
Figure 6.
Figure 6.
Yeast cells lacking components of the ubiquitin/26S proteasome system harbor aberrant mitochondria. Yeast strains were analyzed as in Figure 2. Bar, 5 μm.
Figure 7.
Figure 7.
Yeast cells lacking components of unknown function harbor aberrant mitochondria. Yeast strains were analyzed as in Figure 2. Bar, 5 μm.
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