Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2009
Publication Date: 3/1/2010
Publication URL: http://hdl.handle.net/10113/44842
Citation: Dubovenko, A.G., Dunaevsky, Y.Y., Belozersky, M.A., Oppert, B.S., Lord, J.C., Elpidina, E.N. 2010. Trypsin-like Proteins of the Fungi as Possible Markers of Phytopathogenicity. Fungal Biology. 114: 151-159. doi:10.1016/j.funbio.2009.11.004 Interpretive Summary: Fungal pathogens are often very closely related to benign species that obtain nutrition from non-living material. Distinguishing between these groups is a fundamental requirement for plant protection and selection of biological control agents. From genomic databases, we obtained fungal gene sequences for trypsin, an enzyme that digests proteins. A comparison of fungal species containing trypsin-like sequences revealed that all are pathogens of plants, animals or other fungi. The results support the hypothesis that the expression of trypsins in fungi represents a specific marker of fungal pathogenicity. An evolutionary tree constructed using trypsin-like sequences demonstrated that all sequences have noticeable differences and almost immediately deviate from the common root. Therefore, we conclude that the changes that occurred in trypsins of pathogenic fungi in the course of evolution represent specific adaptations to proteins of their respective hosts, and mutations in trypsin genes permitted association with specific hosts and division into species and genera. This research will aid in selection of targets for plant protection from fungi and agents for biological control of weeds and pest insects.
Technical Abstract: Sequences of peptidases with conserved motifs around the active site residues that are characteristic of trypsins (similar to trypsin peptidases, STP) were obtained from publicly available fungal genomes and related databases. Among the 74 fungal genomes, 30 species of parasitic Ascomycota contained genes encoding STP and their homologs. Searches of non-redundant protein sequences, patented protein sequences, and expressed sequence tags resulted in another 18 STP sequences in 10 fungal species from Ascomycota, Basidiomycota, and Zygomycota. A comparison of fungi species containing STP sequences revealed that almost all are pathogens of plants, animals or fungi. A comparison of the primary structure of homologous proteins, including the residues responsible for substrate binding and specificity of the enzyme, revealed three groups of homologous sequences: trypsin-like peptidases, chymotrypsin-like peptidases and serine peptidases with unknown substrate specificity presumably from the S1 family. Homologs that are presumably functionally inactive were predicted in all groups. The results support the hypothesis that the expression of trypsin-like peptidases in fungi represents a specific marker of fungal phytopathogenicity. A phylogenetic tree was constructed using peptidase and homolog amino acid sequences, demonstrating that all have noticeable differences and almost immediately deviate from the common root. Therefore, we conclude that the changes that occurred in STP of pathogenic fungi in the course of evolution represent specific adaptations to proteins of their respective hosts, and mutations in peptidase genes are important components of life-style changes and taxonomic divergence.