Fig. 5.

Mechanisms suggested to contribute for tolerance to SO₂ in S. ludwigii, as suggested by mining the genome of the UTAD17 strain. The candidate players that might contribute for the enhanced tolerance to SO₂ exhibited by S. ludwigii cells, as suggested by mining of the genome of the UTAD17 strain, were selected and are herein highlighted. Besides the four predicted sulfite exporters with similarity with the sulfite export pump Ssu1 from S. cerevisiae, orthologues for genes that been found to mediate tolerance to SO₂ in S. cerevisiae such as genes involved in biosynthesis of lysine and arginine or the genes involved in the sulfate assimilation pathway, are also indicated. The eventual involvement of a putative Com2-regulatory pathway in S. ludwigii is also hypothesized, based on the existence of a transcription factor with some degree of similarity to this crucial SO₂-determinant in S. cerevisiae (see details for further discussion in the text). It is also hypothesized whether the presumed different structure of the S. ludwigii cell wall, resulting from this species harboring a set of mannoproteins and a different structure of the β-glucan (compared to the one exhibited by in other Saccharomycodeacea species and by Saccharomycetacea) can contribute for the reported reduced diffusion of SO₂ into the inside of S. ludwigii cells [19]. Further information about candidate SO₂-tolerance genes in S. ludwigii is provided in supplementary Table S10. This schematic representation is original and was specifically prepared by the authors to be presented in this manuscript