title: Kluyveromyces lactis killer system: ORF1 of pGKL2 has no function in immunity expression and is dispensable for killer plasmid replication and maintenance.
abstract: To functionally characterize the genes encoded by the larger killer plasmid pGKL2 from Kluyveromyces lactis a previously developed in-vivo recombination system was exploited. An in-vitro modified version of the cytoplasmically expressible LEU2 gene cartridge (LEU2*) flanked by appropriate pGKL2 segments was used to replace the central part of the ORF1 region of pGKL2. Transformation of a Leu- killer strain resulted in the expected disruption of ORF1 in the resident pGKL2. The Leu+ transformants obtained can be assigned to three classes. Class I carries both killer plasmids, pGKL1/2, and the recombinant pGKL2 derivative termed pRKL2. Class II and III additionally harbor palindrome and hairpin-like plasmids, respectively. Upon subculturing of class I transformants under selective pressure, segregation of the native pGKL2 and the recombinant pRKL2 eventually occurs resulting in total loss of pGKL2. No differences concerning killer and immunity phenotype between a pRKL2-harboring strain and the native pGKL2-carrying recipient could be detected. Thus pGKL2 ORF1 is dispensable for both expression of killer/immunity phenotypes and for the replication and maintenance of the K. lactis killer plasmids.
authors.affiliation: Westfälische Wilhelms-Universität Münster, Institut für Mikrobiologie, Federal Republic of Germany.
authors.forename: R
authors.initials: R
authors.lastname: Schaffrath
authors.forename: M J
authors.initials: MJ
authors.lastname: Stark
authors.forename: N
authors.initials: N
authors.lastname: Gunge
authors.forename: F
authors.initials: F
authors.lastname: Meinhardt
mesh_terms: D007109:Immunity / Q000235:genetics; D055646:Killer Factors, Yeast; D007716:Kluyveromyces / Q000235:genetics*; D009183:Mycotoxins / Q000235:genetics*; D016366:Open Reading Frames; D010957:Plasmids / Q000235:genetics*; D014162:Transfection
chemical_list: D055646:Killer Factors, Yeast; D009183:Mycotoxins