Genetic engineering of wine yeast strains requires the identification of gene promoters specifically activated under wine processing conditions. In this study, transcriptional activation of specific genes was followed during the time course of wine fermentation by quantifying mRNA levels in a haploid wine strain of Saccharomyces cerevisiae grown on synthetic or natural winery musts. Northern analyses were performed using radioactive probes from 19 genes previously described as being expressed under laboratory growth conditions or on molasses in S. cerevisiae during the stationary phase and/or under nitrogen starvation. Nine genes, including members of the HSP family, showed a transition-phase induction profile. For three of them, mRNA transcripts could be detected until the end of the fermentation. Expression of one of these genes, HSP30, was further studied using a HSP30::lacZ fusion on both multicopy and monocopy expression vectors. The production of -galactosidase by recombinant cells was measured during cell growth and fermentation on synthetic and natural winery musts. We showed that the HSP30 promoter can induce high gene expression during late stationary phase and remains active until the end of the wine fermentation process. Similar expression profiles were obtained on five natural winery musts. 1997 by John Wiley & Sons, Ltd.