Conversion at large intergenic regions of mitochondrial DNA in Saccharomyces cerevisiae.
Saccharomyces cerevisiae mitochondrial DNA deletion mutants have been used to examine whether base-biased intergenic regions of the genome influence mitochondrial biogenesis. One strain (delta 5.0) lacks a 5-kilobase (kb) segment extending from the proline tRNA gene to the small rRNA gene that includes ori1, while a second strain (delta 3.7) is missing a 3.7-kb region between the genes for ATPase subunit 6 and glutamic acid tRNA that encompasses ori7 plus ori2. Growth of these strains on both fermentable and nonfermentable substrates does not differ from growth of the wild-type strain, indicating that the deletable regions of the genome do not play a direct role in the expression of mitochondrial genes. Examination of whether the 5- or 3.7-kb regions influence mitochondrial DNA transmission was undertaken by crossing strains and examining mitochondrial genotypes in zygotic colonies. In a cross between strain delta 5.0, harboring three active ori elements (ori2, ori3, and ori5), and strain delta 3.7, containing only two active ori elements (ori3 and ori5), there is a preferential recovery of the genome containing two active ori elements (37% of progeny) over that containing three active elements (20%). This unexpected result, suggesting that active ori elements do not influence transmission of respiratory-competent genomes, is interpreted to reflect a preferential conversion of the delta 5.0 genome to the wild type (41% of progeny). Supporting evidence for conversion over biased transmission is shown by preferential recovery of a nonparental genome in the progeny of a heterozygous cross in which both parental molecules can be identified by size polymorphisms.
Skelly
P J
PJ
Research School of Biological Sciences, Australian National University, Canberra.
Clark-Walker
G D
GD
D001483:Base Sequence; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal; D003001:Cloning, Molecular; D004272:DNA, Mitochondrial / Q000235:genetics*; D005785:Gene Conversion; D005800:Genes, Fungal; D005838:Genotype; D006238:Haploidy; D007438:Introns; D008969:Molecular Sequence Data; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid
D004272:DNA, Mitochondrial