ABSTRACT
Some strains of Kluyveromyces lactis contain two linear double-stranded DNA plasmids, k1 and k2. The presence of the two plasmids confer on the cell a "killer" character, due to the production of a toxin that kills the sensitive cells. We have used one of these linear DNA molecules as a gene vector to transform K. lactis cells. Hybrid plasmids containing parts of the k1 plasmid and the URA3 gene of Saccharomyces cerevisiae have been constructed. We have found that the hybrid plasmids were able to transform a uracil-requiring strain of K. lactis (uraA mutant) to a prototrophic form. The transformed phenotype cosegregated with the hybrid plasmids. The transforming plasmids contained the sequence of one or both ends of the linear k1 DNA, but they were integrated into a circular molecule.
Subject(s)
Ascomycota/genetics , Plasmids , Saccharomycetales/genetics , Transformation, Genetic , Base Sequence , DNA Replication , DNA, Fungal/genetics , DNA, Recombinant , Genes , MutationABSTRACT
1. an extrachromosomal, extramitochondrial DNA circle of about 3 µm length, occurring in S. pombe, was cloned in pBR322 and a detailed restriction map of the cloned sequence constructed. 2. Hybridization of this DNA with the ribosomal DNA from S. cerevisiae revealed regions of homology which were mapped in the cloned S. pombe DNA. 3. A transformation system was developed using the URA3 gene of S. cerevisiae and the 3 µm molecule. It was shown that the r-DNA part of the hybrid plasmid promotes replication in S. pombe.
