Stress response and expression patterns in wine fermentations of yeast genes induced at the diauxic shift

During wine fermentation yeasts quickly reach a stationary phase, where cel ls are metabolically active by consuming sugars present in grape must. It i s, consequently, of great interest at this stage to identify suitable gene promoters that may be used to induce the expression of genes with enologica l applications. With this aim, we have studied a group of genes showing an induction peak at the diauxic shift, and possessing stress response element s (STRE) at their promoters. We have determined their induction levels unde r individualized stress conditions, such as carbon source starvation or hig h salt concentrations. In all the cases studied, the activation and/or basa l transcription are dependent on the transcriptional factors Msn2p and Msn4 p. We have analysed the expression patterns and mRNA levels during wine fer mentation, and have found that they are all activated at the stationary pha se. Finally, we have identified SPI1, a new highly expressed yeast gene whi ch is specifically induced at the stationary phase of both microvinificatio n and laboratory growth conditions. Copyright (C) 2000 John Wiley & Sons, L td.