On the basis of the linear killer plasmid pGKL1 from Kluyveromyces lactis, two new linear hybrid plasmids were constructed. One of these, pRSC126, carried the xylA gene from Streptomyces rubiginosus encoding the xylose isomerase. The other linear hybrid molecule, pRSC128, carried the hasB gene of Streptococcus pyogenes encoding the UDP glucose dehydrogenase. Construction was performed in a way that the putative cytoplasmic promoter element of ORF5 of pGKL2 was fused to the coding region of the heterologous genes. After transformation, in vivo recombination led to the establishment of linear hybrid vectors. Though efficiency of expression was low when compared with bacterial systems, cytoplasmic expression of both genes was clearly demonstrated.