microbiology, Vol 140, 1327-1335, Copyright © 1994 by Society for General Microbiology
Linear DNA plasmids from Pichia etchellsii, Debaryomyces hansenii and Wingea robertsiae
YS Cong, D Yarrow, YY Li and H Fukuhara
Institut Curie, Section de Biologie, Centre Universitaire Paris XI, Orsay, France.
Linear DNA plasmids were found in the following yeasts: four strains of
Kluyveromyces lactis, one of Debaryomyces hansenii, one of Wingea
robertsiae and four of Pichia etchellsii. In each case, the plasmids were
present as a pair of DNA molecules of different sizes. The plasmids of K.
lactis strains were associated with a killer activity and their structure
was similar to the known killer plasmids pGKL1 and 2. The plasmids from the
other three species were different from pGKL plasmids and showed no killer
activity against the yeast species tested so far. In all cases, the linear
molecules possessed terminal (probably inverted) repeats and their 5' ends
had a protected structure insensitive to lambda exonuclease, while the 3'
ends were accessible to exonuclease III. All these strains could be
efficiently cured of the plasmids by ultraviolet irradiation. The plasmids
from D. hansenii (pDH1A and B) and from W. robertsiae (pWR1A and B) shared
related sequences with some of the K. lactis killer plasmid genes (encoding
the supposed DNA polymerases, RNA polymerase and the chitinase), suggesting
related genome organization of these plasmids. The pair of plasmids from P.
etchellsii (pPE1A and B) appear to be a distantly related member of the
group. This pair showed no sequence homology with other plasmids, except
weak homology with the putative RNA polymerase gene of pGKL2. None of the
plasmids contained the sequences homologous to ORF3 and ORF4 of pGKL1
encoding the toxin resistance determinant and the toxin gamma subunit,
respectively.
