Study of inheritance of mitochondrial DNA in similar sized rho⁻, hypersuppressive and neutral, in the absence of nuclear gene, MGT1 (mitochondrial genome transmission)

Abstract

Mitochondria DNA is essential for respiration in eukaryotes and essential for life in many organisms including humans. The mechanisms underlying the maintenance and inheritance of both normal and deletion mutants (p) of mitochondrial DNA (mtDNA) in Saccharomyces cerevisiae have not been completely understood. The mtDNA sequence retained in the deletion mutants of S. cerevisiae and the nuclear gene, MGTI, which encodes a recombination junction-resolving endonuclease, are thought to be two important factors in the inheritance and maintenance of an individual mutant mtDNA. There is preliminary evidence that MGTI may be an absolute requirement for maintenance of some mutant mtDNAs but not for others possibly indicating sequence dependent recombination in yeast mtDNA. Hypersuppressive (HS) p and neutral (N) p- are two types of deletion mutants of yeast mtDNA. Both retain only a short fragment of mtDNA, which is amplified to a mass that is equivalent to that of the wild-type mtDNA (p+). HS p- have a replication/segregation advantage over Np- and wild-type p+ mtDNAs that is due to the presence of rep/ori sequences that N p- lack. In these experiments, when HSP- is mated with N p- in the absence of MGTI gene, the resulting cells are all HS p-. This indicates that MGTI gene may not have rep sequence dependent action on preferential inheritance.