Immuno-electron localization of DNA in chondriolites of Saccharomyces cerevisiae mitochondria
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Published on: March 14, 2014
1Institute of Microbiology, Academy of Sciences of Czech Republic, 142 20 Prague, Czechia.
Abstract:
Under electron microscope, the matrix of sectioned mitochondria exhibits ribosomes and an oval, electron-transparent zone which is devoid of ribosomes and is named chondriolite. Fine fibers or clumps of an electron-dense material appeared in this zone after several fixation and contrasting steps and were identified with mitochondrial DNA by cytologists. To verify this assumption, we labeled DNA by a monoclonal antibody and a secondary antibody coupled to immunogold. The label was observed in the nucleus and in the chondriolite zone of sectioned mitochondria. Because the ultrastructure of chondriolites resembles that of nucleoids of prokaryotes, we suggest the term mitochondrial nucleoid for the zone of mitochondrial matrix devoid of ribosomes and containing DNA.
Insights
Researchers identified mitochondrial DNA within a ribosome-free zone in mitochondria, termed the chondriolite. This discovery supports the concept of a mitochondrial nucleoid, similar to prokaryotic nucleoids.
Area of Science:
- Cell Biology
- Mitochondrial Biology
- Molecular Genetics
Background:
- Mitochondrial matrix contains ribosomes and a distinct electron-transparent zone called chondriolite.
- Cytological studies suggested the presence of mitochondrial DNA within chondriolites.
- The ultrastructure of chondriolites bears resemblance to prokaryotic nucleoids.
Purpose of the Study:
- To definitively identify and localize mitochondrial DNA within the chondriolite.
- To investigate the structural and functional implications of the chondriolite.
- To propose a standardized term for this mitochondrial compartment.
Main Methods:
- Electron microscopy was used to visualize mitochondrial ultrastructure.
- Immunogold labeling with a monoclonal antibody against DNA was performed.
- Secondary antibodies coupled to immunogold were used for detection.
Main Results:
- Electron-dense material, identified as DNA, was observed within the chondriolite zone.
- The DNA label was localized to the chondriolite in sectioned mitochondria.
- DNA labeling was also observed in the nucleus, serving as a positive control.
Conclusions:
- The chondriolite represents a mitochondrial compartment containing DNA.
- The term 'mitochondrial nucleoid' is proposed for this ribosome-free, DNA-containing zone.
- This finding highlights similarities between mitochondrial organization and prokaryotic nucleoids.
