Fungal lifestyle reflected in serine protease repertoire

Abstract

Fungi are able to switch between different lifestyles in order to adapt to environmental changes. Their ecological strategy is connected to their secretome as fungi obtain nutrients by secreting hydrolytic enzymes to their surrounding and acquiring the digested molecules. We focus on fungal serine proteases (SPs), the phylogenetic distribution of which is barely described so far. In order to collect a complete set of fungal proteases, we searched over 600 fungal proteomes. Obtained results suggest that serine proteases are more ubiquitous than expected. From 54 SP families described in MEROPS Peptidase Database, 21 are present in fungi. Interestingly, 14 of them are also present in Metazoa and Viridiplantae - this suggests that, except one (S64), all fungal SP families evolved before plants and fungi diverged. Most representatives of sequenced eukaryotic lineages encode a set of 13-16 SP families. The number of SPs from each family varies among the analysed taxa. The most abundant are S8 proteases. In order to verify hypotheses linking lifestyle and expansions of particular SP, we performed statistical analyses and revealed previously undescribed associations. Here, we present a comprehensive evolutionary history of fungal SP families in the context of fungal ecology and fungal tree of life.

Figure 1

A Venn diagram representing the numbers of SP families shared in selected lineages of Eukaryota (A) and in main lineages of Opistokonta (B). The image was prepared using Draw Venn Diagram – Ugent.

Figure 2

Summary of taxonomic distribution of 21 SP families in Fungi. The image was prepared with iTOL. Schematic tree was drawn based on classification by Spatafora and colleagues.

Figure 3

Correlations between SP abundance and proteome (A) or genome size (B). Points were coloured according to classification to fungal phyla. (C) The abundance of SP families within fungal proteomes. The image was prepared in Jupyter Notebook with matplotlib and seaborn packages.

Figure 4

Relationships between defined lifestyle features and serine protease abundance. Colour intensities correspond to the coefficient values of the linear regression models; each column is scaled according to the maximum value; white cells depict no correlation or statistically insignificant relation.