Restriction site variation, length polymorphism and changes in gene order in the mitochondrial DNA of the yeast Kluyveromyces lactics.

The purpose of this work was to compare mitochondrial DNA restriction endonuclease patterns in strains of the yeast Kluyveromyces lactis, from different sources, to see how conserved is the organization of this organellar genome. The mitochondrial DNA of five independently-isolated strains and one of unknown origin were compared. Strains NRRL Y-1205, NRRL Y-8279 and NRRL Y-1140 gave identical patterns. Strain NRRL Y-1564 showed an insertion, with respect to the other three, of approximately 1250 bp. Strain W600B had also an insertion with extra restriction sites for EcoRI, HpaI, HaeIII, HincII and XbaI. On the other hand, strain Y-123 showed a restriction pattern quite different from the others. Sequences putatively encoding apocytochrome b, ATPase subunit 9 and ribosomal RNA large subunit, were localized on the physical maps of three strains. Results demonstrated that the order of these three genes shows a common feature in strains W600B and WM37 (auxotroph of Y-1140) but a different distribution in WM27 (auxotroph derived from Y-123). All these facts explain the extensive intraspecific polymorphism observed in the mtDNA of this yeast.