Multiple pathways influence mitochondrial inheritance in budding yeast - PubMed (original) (raw)

Multiple pathways influence mitochondrial inheritance in budding yeast

Rebecca L Frederick et al. Genetics. 2008 Feb.

Abstract

Yeast mitochondria form a branched tubular network. Mitochondrial inheritance is tightly coupled with bud emergence, ensuring that daughter cells receive mitochondria from mother cells during division. Proteins reported to influence mitochondrial inheritance include the mitochondrial rho (Miro) GTPase Gem1p, Mmr1p, and Ypt11p. A synthetic genetic array (SGA) screen revealed interactions between gem1Delta and deletions of genes that affect mitochondrial function or inheritance, including mmr1Delta. Synthetic sickness of gem1Delta mmr1Delta double mutants correlated with defective mitochondrial inheritance by large buds. Additional studies demonstrated that GEM1, MMR1, and YPT11 each contribute to mitochondrial inheritance. Mitochondrial accumulation in buds caused by overexpression of either Mmr1p or Ypt11p did not depend on Gem1p, indicating these three proteins function independently. Physical linkage of mitochondria with the endoplasmic reticulum (ER) has led to speculation that distribution of these two organelles is coordinated. We show that yeast mitochondrial inheritance is not required for inheritance or spreading of cortical ER in the bud. Moreover, Ypt11p overexpression, but not Mmr1p overexpression, caused ER accumulation in the bud, revealing a potential role for Ypt11p in ER distribution. This study demonstrates that multiple pathways influence mitochondrial inheritance in yeast and that Miro GTPases have conserved roles in mitochondrial distribution.

PubMed Disclaimer

Figures

F<sc>igure</sc> 1.—

Figure 1.—

Synthetic interactions among _gem1_Δ and genes that affect Myo2p-dependent mitochondrial inheritance (MMR1 and YPT11) revealed that multiple pathways contribute to strain viability. _gem1_Δ _mmr1_Δ (A) and _mmr1_Δ _ypt11_Δ (C) double mutants displayed growth defects. _gem1_Δ _ypt11_Δ (B) double mutants grew as well as either single mutant. _gem1_Δ _mmr1_Δ _ypt11_Δ (D) triple mutants germinated poorly and grew very slowly (doubling time >12 hr). Diploid W303 strains with the partial genotypes indicated at the top were dissected, and the four progeny from a single tetrad were arranged in vertical columns. Each spore genotype is indicated by a symbol in the bottom sections corresponding to its position in the top.

F<sc>igure</sc> 2.—

Figure 2.—

Mitochondrial inheritance defects correlated with reduced viability in synthetic double mutants. (A, B, D, and E) Examples of successful mitochondrial inheritance. (C and F) Examples of defective mitochondrial inheritance. (G and H) Examples of severely reduced mitochondrial inheritance (≤2 mitochondrial pieces per bud). Representative small- (A–C) and large- (D–H) budded cells of wild type (A and D) and _gem1_Δ _mmr1_Δ (B, C, and E–H) cultures. (I) Quantification of small- (shaded bars) and large- (solid bars) budded inheritance in strains of the indicated genotype. Presence of any mitochondria in the bud was scored as successful mitochondrial inheritance. Signal derived from mito-GFP was overlaid on the DIC image in this and other figures. N ≥ 150 for each genotype and bud size. Error bars indicate standard deviation between at least three independent experiments in this and other figures. Bar, 5 μm.

F<sc>igure</sc> 3.—

Figure 3.—

Mmr1p or Ypt11p overexpression cause mitochondria to accumulate in buds independent of Gem1p function. (A–G) Mmr1p overexpression was achieved by galactose induction for 1 hr after preculture in raffinose. (A and D) GEM1 and _gem1_Δ strains containing empty vector. (B and E) Mitochondria accumulated in the bud of wild-type and _gem1_Δ strains. (C and F) Mitochondria accumulated at the bud neck of wild-type and _gem1_Δ strains. (G) Quantification of accumulation at the bud or bud neck region in control cells (shaded bar) and cells overexpressing Mmr1p (solid bar) of the indicated genotype. n ≥ 300 budded cells. (H–N) Ypt11p overexpression. (H and K) GEM1 and _gem1_Δ cells containing empty vector. (I, J, L, and M) Representative images of GEM1 and _gem1_Δ cells grown in medium lacking methionine for 3 hr to overexpress _MET25_-driven YPT11. (N) Quantification of mitochondrial accumulation in control experiments (shaded bars) or during Ypt11p overexpression (solid bars) in strains of the indicated genotypes. n ≥ 300 medium and large-budded cells. Bar, 5 μm.

F<sc>igure</sc> 4.—

Figure 4.—

Mitochondrial inheritance did not influence distribution of ER in the bud. Sections from left to right are DIC, mito-RFP deconvolved projection, Hmg1p-GFP-labeled ER deconvolved single _z_-sections at the periphery, and at the center of the cell. Inheritance and distribution of ER in wild type (A), and _gem1_Δ _mmr1_Δ (B) to the cortex of small buds is evident, regardless of mitochondrial inheritance status. (C) _ptc1_Δ mutant cells display inheritance of a single ER tubule but do not appropriately distribute ER to the cortex of small buds. Arrowheads mark the mother-bud neck. (D) Quantification reveals that mitochondrial inheritance is not a prerequisite for ER inheritance and cortical distribution. In the schematic, cortical ER is represented by shaded and mitochondria by solid lines. Bar, 5 μm.

F<sc>igure</sc> 5.—

Figure 5.—

Overexpression of Ypt11p caused ER to accumulate in buds regardless of mitochondrial distribution. Sections from left to right are DIC, mito-RFP deconvolved projection, Ssh1p-GFP-labeled ER deconvolved single _z_-sections at the periphery, and at the center of the cell. (A) Wild-type cells expressing empty vector. (B) Overexpression of YPT11 as in Figure 3. (C) Quantification revealed that ER accumulates in buds during Ypt11p overexpression but not Mmr1p overexpression. Arrowheads mark the mother-bud neck. Bar, 5 μm.

Similar articles

Cited by

References

    1. Altmann, K., and B. Westermann, 2005. Role of essential genes in mitochondrial morphogenesis in Saccharomyces cerevisiae. Mol. Biol. Cell 16 5410–5417. - PMC - PubMed
    1. Boldogh, I., N. Vojtov, S. Karmon and L. A. Pon, 1998. Interaction between mitochondria and the actin cytoskeleton in budding yeast requires two integral mitochondrial outer membrane proteins, Mmm1p and Mdm10p. J. Cell Biol. 141 1371–1381. - PMC - PubMed
    1. Boldogh, I. R., H. C. Yang and L. A. Pon, 2001. Mitochondrial inheritance in budding yeast. Traffic 2 368–374. - PubMed
    1. Boldogh, I. R., D. W. Nowakowski, H. C. Yang, H. Chung, S. Karmon et al., 2003. A protein complex containing Mdm10p, Mdm12p, and Mmm1p links mitochondrial membranes and DNA to the cytoskeleton-based segregation machinery. Mol. Biol. Cell 14 4618–4627. - PMC - PubMed
    1. Boldogh, I. R., S. L. Ramcharan, H. C. Yang and L. A. Pon, 2004. A type V myosin (Myo2p) and a Rab-like G-protein (Ypt11p) are required for retention of newly inherited mitochondria in yeast cells during cell division. Mol. Biol. Cell 15 3994–4002. - PMC - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources