Pathogenicity factors of Phytophthora melonis revealed by comparative proteomics

Abstract

Deciphering the transcriptional activities of pathogenicity genes is critical to understand pathogenesis mechanisms of Phytophthora melonis, a devastating pathogen of cucurbits. In this study, we have performed comparative proteomics among P. melonis mutants to evaluate the interacting pathogenicity proteins. Structural characterization of all detected proteins discovered the physicochemical factors behind their pathogenic behavior. Results revealed that gamma radiations have an extreme potential to mutate P. melonis spores, and can be a safe alternative of chemical mutagens. P. melonis is accomplished with seventy-three differentially expressed proteins among which, seven proteins were ranked as strong pathogenicity factors, i.e. Q9AT01 (Elicitin), D0MX11 (Oligopeptidase A, putative), D0NB60 (Secreted RXLR effector peptide protein, putative), D0NIK4 (IpiB3-like protein), D0NIZ1 (Carboxypeptidase), H3GZF4 and H3GZF6. The Ramachandran plot determined the positions of secondary structures (α helix and β sheets) in the 3D structures of pathogenicity proteins. Furthermore, the glycine residues analysis highlighted that six out of seven proteins were functionally and structurally more stable than D0NIK4 protein. The study concluded that the pathogenic proteins must have negative ϕ angles greater than 63°, and ψ angles ≥80° for their proper functioning. This study establishes functional connections between pathogenicity genes and the process of disease establishment.