One sentence summary: The authors investigated the mitochondrial nucleoids in Saccharomyces cerevisiae and found that the morphology of mitochondrial nucleoids in rho -cells significantly varies depending on the unit length of their mtDNA.Editor: Monique Bolotin-Fukuhara
ABSTRACTWe investigated the morphology of mitochondrial nucleoids (mt-nucleoids) and mitochondria in Saccharomyces cerevisiae rho + and rho − cells with DAPI staining and mitochondria-targeted GFP. Whereas the mt-nucleoids appeared as strings of beads in wild-type rho + cells at log phase, the mt-nucleoids in hypersuppressive rho − cells (HS40 rho − cells) appeared as distinct punctate structures. In order to elucidate whether the punctate mt-nucleoids are common to other rho − cells, we observed the mt-nucleoids in rho − strains that retain different unit lengths of the mitochondrial DNA (mtDNA) sequence.As a result, rho − cells that have long mtDNA sequences, of more than 30 kb, had mt-nucleoids with a strings-of-beads appearance in tubular mitochondria. In contrast, rho − cells that have short mtDNA sequences, of <1 kb, had punctate mt-nucleoids in tubular mitochondria. This indicates that the morphology of mt-nucleoids in rho − cells significantly varies depending on the unit length of their mtDNA sequence. Analyses of mt-nucleoids suggest that the punctate mt-nucleoids in HS40 rho − cells consist of concatemeric mtDNAs and oligomeric circular mtDNAs associated with Abf2p and other nucleoid proteins.