Expression and role of CYP505A1 in pathogenicity of Fusarium oxysporum f. sp. lactucae

Background: Cytochrome P450 enzymes (CYPs) are monooxygenases present in every domain of life. In fungi CYPs are involved in virulence. Fusarium wilt of lettuce, caused by F. oxysporum f. sp. lactucae, is the most serious disease of lettuce. F. oxysporum f.sp. lactucae MSA35 is an antagonistic fungus. Pathogenic formae specialis of F. oxysporum possess a CYP belonging to the new family CYP505. This enzyme hydroxylates saturated fatty acids that play a role in plant defence. Methods: Molecular tools were adopted to search for cyp505 gene in MSA35 genome. cyp505 gene expression analysis in pathogenic and antagonistic Fusarium was performed. The enzyme was expressed in its recombinant form and used for catalytic reactions with fatty acids, the products of which were characterized by mass spectrometry analysis. Results: A novel MSA35 self-sufficient CYP505 is differentially expressed in antagonistic and pathogenic F. oxysporum. Its expression is induced by the host plant lettuce in both pathogenesis and antagonism during the early phase of the interaction, while it is silenced during the late phase only in antagonistic Fusarium. Mass-spectrometry investigations proved that CYP505A1 mono-hydroxylates lauric, palmitic and stearic acids. Conclusions: The ability of CYP505A1 to oxidize fatty acids present in the cortical cell membranes together with its differential expression in its Fusarium antagonistic form point out to the possibility that this enzyme is associated with Fusarium pathogenicity in lettuce. General significance: The CYP505 clan is present in pathogenic fungal phyla, making CYP505A1 enzyme a putative candidate as a new target for the development of novel antifungal molecules.