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Role of MMM1 in maintaining mitochondrial morphology in Neurospora crassa
H Prokisch1, W Neupert, B Westermann
1Institut für Physiologische Chemie der Universität München, Goethestrasse 33, 80336 München, Germany.
Abstract:
Mmm1p is a protein required for maintenance of mitochondrial morphology in budding yeast. It was proposed that it is required to mediate the interaction of the mitochondrial outer membrane with the actin cytoskeleton. We report the cloning and characterization of MMM1 of the filamentous fungus Neurospora crassa, an organism that uses microtubules for mitochondrial transport. Mutation of the mmm-1 gene leads to a temperature-sensitive slow growth phenotype and female sterility. Mutant cells harbor abnormal giant mitochondria at all stages of the asexual life cycle, whereas actin filament-depolymerizing drugs have no effect on mitochondrial morphology. The MMM1 protein has a single transmembrane domain near the N terminus and exposes a large C-terminal domain to the cytosol. The protein can be imported into the outer membrane in a receptor-dependent manner. Our findings suggest that MMM1 is a factor of general importance for mitochondrial morphology independent of the cytoskeletal system used for mitochondrial transport.
Insights
Mmm1p protein maintains mitochondrial shape in yeast by interacting with the actin cytoskeleton. In Neurospora crassa, MMM1 is crucial for mitochondrial morphology, independent of the microtubule transport system.
Area of Science:
- Cell Biology
- Mycology
- Genetics
Background:
- Mmm1p protein is essential for mitochondrial morphology in budding yeast.
- Previous studies suggested Mmm1p mediates mitochondrial outer membrane interaction with the actin cytoskeleton.
Purpose of the Study:
- To clone and characterize the MMM1 gene in the filamentous fungus Neurospora crassa.
- To investigate the role of MMM1 in mitochondrial morphology and function, particularly in an organism utilizing microtubules for mitochondrial transport.
Main Methods:
- Gene cloning and characterization of MMM1 in Neurospora crassa.
- Phenotypic analysis of mmm-1 mutants, including growth, fertility, and mitochondrial morphology.
- Assessment of actin filament integrity and its effect on mitochondria in mutant cells.
Main Results:
- Mutation of the mmm-1 gene resulted in temperature-sensitive slow growth and female sterility.
- Mutant cells exhibited abnormal giant mitochondria across all asexual life cycle stages.
- Actin filament-depolymerizing drugs did not affect mitochondrial morphology in mutant cells, suggesting MMM1's role is independent of actin.
Conclusions:
- MMM1 is essential for maintaining mitochondrial morphology in Neurospora crassa.
- The function of MMM1 in mitochondrial morphology is independent of the cytoskeletal system (microtubules or actin) used for mitochondrial transport.
- MMM1 is a broadly important factor for mitochondrial morphology across different eukaryotic organisms.