Isolation and characterization of linear deoxyribonucleic acid plasmids from Kluyveromyces lactis and the plasmid-associated killer character

Abstract

Two linear deoxyribonucleic acid plasmids, designated pGKll and pGK12, were isolated from the yeast Kluyveromyces lactis IFO 1267. pGKll and pGK12 had molecular weights of 5.4 x 106 and 8.4 x 106, respectively. Both plasmids possessed the same density of 1.687 g/cm3, lighter than the densities of mitochondrial (1.692 g/cm3) and nuclear (1.699 g/cm3) deoxyribonucleic acids. A restriction map of pGKll was constructed from digestions by EcoRI, HindIII, PstI, and BamHI. pGK12 was cleaved by EcoRI into seven fragments and by BamHI into two fragments. K. lactis IFO 1267 killed Saccharomyces cerevisiae sensitive and killer strains and certain strains of Saccharomyces italicus, K. lactis, Kluyveromyces thermotolerans, and K. vanudenii. All K. lactis strains lacking the pGKl plasmids were nonkillers. A hybrid was constructed between K. lactis IFO 1267 and a nonkiller K. lactis strain lacking the plasmids and subjected to tetrad analysis after sporulation. The killer character was extrachromosomally transmitted in all tetrads in association with the pGKI plasmids. The double-stranded ribonucleic acid killer plasmid could not be detected in any K. lactis killer strains. It is thus highly probable that the killer character is mediated by the linear deoxyribonucleic acid plasmids. A single chromosomal gene was found which was responsible for the resistance to the K. lactis killer.

The primary target of the killer toxin from Pichia acaciae is tRNAGln

“…A toxin (termed zymocin) comparable to PaT is encoded by linear plasmids of the yeast Kluyveromyces lactis (Gunge et al, 1981). Zymocin possesses a subunit highly homologous to the chitin-binding protein of PaT and, as for the latter, it was shown to mediate cell wall binding (Jablonowski et al, 2001).…”

The mechanisms of epigenetic inheritance: how diverse are they?

“…In eukaryotes, multiple examples of non-chromosomal inheritance have been traditionally associated with mitochondrial, plastid, or plasmid genes (Gunge et al, 1981;Gillham, 1994;Reboud & Zeyl, 1994). However, in the 1990s some non-chromosomal hereditary factors were shown to be prions (the term prion means 'infectious protein'; see Prusiner, 1998;Wickner et al, 2000).…”

Killer Factor as a Mechanism of Interference Competition in Yeasts Associated with Cacti

“…There are several types of killer toxins with different genetics, modes of transmission, and physical properties. Killer toxin and immunity genes may be transmitted cytoplasmically and may reside on doublestranded RNA virus-like particles (Wickner 1981) or in pairs of linear, double-stranded DNA plasmids (Gunge et al 1981). In some killer species there is no indication that the killer trait is located in the cytoplasm (Young and Yagiu 1978, Gunge 1986, Starmer et al 1987a, Yokomori et al 1988, Zorg et al 1988, Goto et al 1990).…”