LysM effectors of various fungal species contribute to pathogen virulence

SP-08 LysM effectors of various fungal species contribute to pathogen virulence Anja Kombrink Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands Putative LysM effectors are found in a wide range of fungal species. LysM effectors are defined as secreted proteins that contain a signal peptide, a varying number of LysM domains and no other recognizable domain. LysM domains are known as carbohydrate-binding modules. The first characterized LysM effector, designated Ecp6, from Cladosporium fulvum was shown to be instrumental for virulence of the fungus on tomato and carbohydrate binding assays demonstrated that Ecp6 specifically interacts with chitin. Chitin is the major constituent of the fungal cell wall and acts as PAMP upon recognition by the plant during fungal invasion. However, the presence of chitin-binding effector Ecp6 in the apoplast interferes with the perception of chitin by plant receptors and in this manner prevents the activation of defense responses. Two orthologues of Ecp6 are identified in Mycosphaerella graminicola of which one was demonstrated to supress chitin induced defense responses, like Ecp6. Interestingly, unlike Ecp6, both orthologues were able to inhibit degradation of fungal hyphae by plant chitinases. To further study the role of LysM effectors in other fungal species, the LysM effector family of Verticillium dahliae is being investigated. The V. dahliae genome contains 7 putative LysM effectors and we hypothesize that not all bind chitin and that some play a role during other fungal stages than plant infection. V. dahliae LysM effector functions are currently investigated through carbohydrate binding studies of the proteins and phenotyping of LysM effector gene knock-out mutants.