Spatial and temporal dynamics of budding yeast mitochondria lacking the division component Fis1p

Abstract

The mitochondrial compartment of budding yeast (Saccharomyces cerevisiae) is a highly dynamic net-like structure of tubules that constantly undergo fusion and fission. The outer membrane protein Fis1p plays a crucial role in mitochondrial fission. Here we report on the temporal and spatial dynamics of this organelle in wild-type cells and in fis1Δ mutants. Mitochondria of fis1Δ mutants adapt their mitochondrial network to a change in carbon source. We find that the frequencies of apparent matrix separation and fusion events decrease in both wild-type cells and in mutants lacking Fis1p upon glucose repression. Matrix separation could be caused by matrix constriction and does not necessarily require fission of the inner or outer membrane. Double-labelling experiments demonstrated that some of these matrix separations in fis1 mutants are due to genuine tubule fissions, whereas others do not involve fission of the outer membrane. The rates of matrix separation in fis1Δ mutants almost approach those of the wildtype,demonstrating that, although apparently involved in outer membrane fission,Fis1p is not crucial for the separation of the mitochondrial matrix. In mutants lacking the GTPase Dnm1p no complete tubule fissions were recorded,although dnm1Δ mutants display matrix separations as well. The data suggest that different molecular machineries are responsible for the separation of the matrix and the fission of the outer membrane in budding yeast.

Nonredundant Roles of Mitochondria-associated F-Box Proteins Mfb1 and Mdm30 in Maintenance of Mitochondrial Morphology in Yeast

“…Volume, number, and morphology of mitochondria are readily adapted to the carbon source of the growth medium and oxygen supply (Stevens, 1981;Visser et al, 1995;Egner et al, 2002;Jakobs et al, 2003). During mitotic growth, mating, and sporulation, mitochondria are partitioned to newly formed cells by highly ordered inheritance mechanisms and dynamic remodeling processes (Miyakawa et al, 1984;Nunnari et al, 1997;Simon et al, 1997;Okamoto et al, 1998;Yang et al, 1999;Gorsich and Shaw, 2004).…”

“…Plasmid pYES-MDM30 for expression of Mdm30 from the GAL1 promoter has been described previously (Fritz et al, 2003). Plasmids pVT100U-mtGFP, pYX113-mtGFP (Westermann and Neupert, 2000), pRS416-GAL1ϩPrF 0 ATP9-RFP (Mozdy et al, 2000), and pSJ55 (Jakobs et al, 2003) were used for expression of mitochondria-targeted green fluorescent protein (GFP) or mitochondria-targeted DsRed. Plasmids for expression of FLAG-tagged Mdm30 and an F-box-less variant thereof under control of the CUP1 promoter are described by Escobar-Henriques et al (2006).…”

“…Defects in cells lacking components of the fusion machinery can be relieved by deletion of genes encoding proteins of the fission machinery (Bleazard et al, 1999;Sesaki and Jensen, 1999). Wild-type cells growing logarithmically on glucose-containing medium show tightly balanced mitochondrial fusion and fission activities at a rate of 1.7 fusion and fission events per minute and cell (Jakobs et al, 2003). Thus, fusion and fission must be strictly coordinated to maintain a reticular mitochondrial network.…”

Mitochondrial fission proteins regulate programmed cell death in yeast

“…However, we cannot rule out the possibility that the mitochondrial fragments in ⌬dnm1 mutant cells remain linked in some manner due to incomplete severing of mitochondrial tubules. Interestingly, time-lapse monitoring of mitochondrial fission in ⌬dnm1 also failed to detect fission events that were not rapidly rejoined, unlike ⌬fis1 mutant yeast (Jakobs et al 2003).…”

Quantitative 3-D imaging of eukaryotic cells using soft X-ray tomography

“…Yeast is a particularly good model system for studying the size, shape, and distribution of organelles such as mitochondria as a means of coping with changes in their environment (Anesti and Scorrano, 2006;Hales, 2004;Hermann and Shaw, 1998;Hoog et al, 2007;Jakobs et al, 2003;Jensen, 2005;Logan, 2003;Logan, 2006;Sun et al, 2007;Yaffe et al, 1996). For example, during logarithmic growth the mitochondria in yeast constantly undergo fusion and fission.…”