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The Saccharomyces bayanus var. uvarum yeasts are associated with spontaneous fermentation of must. Some strains were shown to be enological yeasts of interest in different winemaking processes. The molecular typing of S. bayanus var. uvarum at the strain level has become significant for wine microbiologists. Four microsatellite loci were defined from the exploration of genomic DNA sequence of S. bayanus var. uvarum. The 40 strains studied were homozygote for the locus considered. The discriminating capacity of the microsatellite method was found to be equal to that of karyotypes analysis. Links between 37 indigenous strains with the same geographic origin could be established through the analysis of microsatellite patterns. The analysis of microsatellite polymorphism is a reliable method for wine S. bayanus var. uvarum strains and their hybrids with Saccharomyces cerevisiae identification in taxonomic, ecological studies and winemaking applications.

As previous studies indicated that the RVS161 and RVS167 gene products of Saccharomyces cerevisiae seem to be involved in the same cellular function, we considered the possibility of a complex between the proteins encoded by these two genes. Using the two hybrid system, we have shown that Rvs167p interacts with Rvs161p, through its N-terminal domain which contains predicted coiled-coil structures. Moreover, if a tagged Rvs 167p protein was immuno adsorbed under non-denaturing conditions, it brought along the Rvs161p protein. These results confirmed the hypothesis of an in vivo complex between the two proteins.

A mutant strain of Podospora anserina (modF) showed several altered properties of protoperithecial formation on a solid medium, including an accelerated timing of appearance, a high density (more than 10-fold higher than wild-type strains), and a shortened functional longevity of protoperithecia. Comparative growth features of mutant and wild-type strains were determined by culture in various liquid synthetic media limited for one of the basic nutrients. Dry weight production time courses of wild-type and mutant cultures differed only when the carbon source was glucose and when glucose was the limiting nutrient of the culture medium. Under these conditions, mutant cultures resulted in an excess of dry weight production and showed a reduction of cell life span following glucose exhaustion. However, despite their divergence in survival, mutant and wild-type cells did not significantly differ in the amount of their reserves in glycogen and trehalose. Comparison of dry weight increases by mutant and wild-type strains showed that the glucose-requiring growth control which reduced the proliferation of wild-type cultures is related neither to the concentration of glucose available nor to the amount of glucose consumed, but to the age of cultures. It is presumed that the modF strain is defective in a growth control which is expected to result in a quiescent stage specific to nonapical cells that confers resistance against glucose starvation.

The structure of ATP synthase subunit 4 was determined by using the oligonucleotide probe procedure. This subunit is the fourth polypeptide of the complex when classifying subunits in order of decreasing molecular mass. Its relative molecular mass is 25 kDa. The ATP4 gene was isolated and sequenced. The nucleotide sequence predicts that subunit 4 is probably derived from a precursor protein 244 amino acids long. Mature subunit 4 contains 209 amino acid residues and the predicted molecular mass is 23250 kDa. Subunit 4 shows homology with the b-subunit of Escherichia coli ATP synthase and the b-subunit of beef heart mitochondrial ATP synthase. By using homologous transformation, a mutant lacking wild subunit 4 was constructed. This mutant is devoid of oxidative phosphorylation and F1 is loosely bound to the membrane. Our data are in favor of a structural relationship between subunit 4 and the mitochondrially-translated subunit 6 during biogenesis of F0.

In Podospora anserina three allelic mutations (of modD ) were defective in ascospore germination, protoperithecium formation, and growth renewal from stationary cells. To investigate the action of the modD gene a mutation ( modE ) was selected, which suppresses the developmental defects associated with a modD mutation ( modD(2) ). The comparison of modD, modE, modD, modE , and wild-type strains gave the following results: (i) each mutant showed a specific and large spectrum of variations in the level of the in vivo resistance to unrelated drugs (cycloheximide, sorbose, thiourea, ethionine); (ii) the protoplasts isolated from the modE strain were osmotic fragile at elevated temperatures; (iii) the temperature at which the osmotic fragility associated with modE inhibits growth, in a medium of a standard osmotic pressure, was strongly dependent on modD mutations. Furthermore, the coupling of the modD(1) mutation to modC(1) , a mutation which is known to inhibit growth at acid pH (6.5), resulted in a strain with a wild-type pH dependence. Considered together these results suggest that the modD developmental mutations could be, like modE , responsible for a modification of plasma membrane properties.