Résumé
Oligopeptides are commonly found in nature as the result of proteolytic processes. The capacity to consume oligopeptides can represent an adaptive advantage for organisms within an ecological niche, since they can be used as a source of nitrogen. However, certain oligopeptides are toxic and thus their import can be a potentially lethal trait. Genes responsible for oligopeptide transport are generally not essential, so they are more prone to be lost; furthermore, genes present in a species as a result of horizontal gene transfer (HGT) are often non-essential genes. In the first description of the Fungal Oligopeptide Transporters (Fot), they were defined as a new family of di- and tripeptide transporters only found in fungal species of Ascomycota and Basidiomycota. In this work, we expanded the search for Fot orthologues through a curated strategy that confirmed the presence of Fot in all the main subphyla of Dikarya, suggesting that this is an ancestral-segregating family of genes in fungi. The patchy presence of Fot among the species of Pezizomycotina, not following the taxonomy of the species, is indicative of several gene losses and possible re-acquisitions by HGT. Similarly, Fot are found among the major clades described in Saccharomycotina, particularly of note in Dipodascaceae/Trichomonascaceae. Besides the recent HGT event identified between Torulaspora microellipsoides and Saccharomyces cerevisiae wine strains, here we propose other HGT that may have taken place earlier in evolution, between the ancestors of the Starmerella/Wickerhamiella clade, Phaffomycetaceae and Saccharomycetaceae. In summary, the complex distribution displayed by Fot is reflective of the conflicting evolutionary pressures that the oligopeptide consumption trait may entail for fungi