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Unique structure of the Ccw7 cell wall proteins and the encoding genes of ˝Tokaji szamorodni˝ film-forming wine yeast strain

During maturation of the Hungarian botrytized wine ˝Tokaji szamorodni˝ a buoyant film develops on the wine surface, which is similar to the flor or velum formed during aging of sherry wines. In both cases the yeast films play an important role in the formation of aroma compounds that are responsible for the typical organoleptic characters of these wines. Our aims were the characterization of cell wall proteins of film-forming and non-film forming (sedimenting) wine yeast strains and finding protein candidates that were playing role in the establishment of special cell surface structure. As the first step of research the patterns of biotinylated cell wall proteins extracted from film-forming and non-film forming Saccharomyces cerevisiae strains were compared. It was found that all of the tested 23 film-forming ˝Szamorodni˝ yeast strains had a decreased size of the Ccw7 protein, one of the members of the Pir-protein family. Sequencing of the encoding genes revealed that the strains were lacking three out of the eleven repeating sequences characteristic to this protein family. One of the film-forming strains contained CCW7 alleles of different length, what was generated by intragenic tandem duplication of a sequence containing two repetitive domains. Unlike the film-forming strains, sixteen non-film forming wine yeasts isolated from a different botrytized wine, ˝Tokaji Aszu˝ showed pronounced polymorphism of the CCW7 locus. It is highly probable that the modified Ccw7 protein contribute to the stress adaptation during film-formation.

cell wall; Pir proteins; CCW7; Tokaji szamorodni

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