To analyse the molecular mechanism by which a mating pheromone signal is transmitted in Saccharomyces kluyveri, the S. cerevisiae FUS1-lacZ fusion gene was introduced into S. kluyveri cells and its transcriptional activation was investigated. The expression of FUS1-lacZ fusion product was cell-type-specifically induced by pheromone treatment in S. kluyveri. The result suggests that S. kluyveri pheromone signal may be transduced by a mechanism similar to that in S. cerevisiae. This system may provide a model for analysing the molecular mechanism of the mating reaction in Saccharomyces kluyveri.