Expression of mitochondrial aldehyde dehydrogenase genes
Mitochondrial enzymes are encoded by the ALD4 and ALD5 genes. Figure 1 shows the results of our analyses of the expression of these genes under several conditions. Panel A shows Northern blot analyses corresponding to C strain [the flor yeast with higher acetaldehyde resistance among the strains considered (Aranda et al., 2002) and hence our reference and model system for this study] in different growth media (glucose or ethanol as carbon sources) and under acetaldehyde and ethanol addition. Panel B quantifies transcription induction or repression of ALD4 gene caused by sudden ethanol or acetaldehyde addition to yeast cells, of all the strains considered, growing in both media. Panel C indicates the basal mRNA levels of this gene (relative to those found for C strain) when the cells are grown exponentially in glucose or ethanol as carbon source. The expression of ALD5, encoding the minor mitochondrial acetaldehyde dehydrogenase was too low for an accurate determination of the differences between growth conditions and strains and only an overexposure of one of the films obtained is included in panel A.