Role of effector proteins secreted by Cladosporium fulvum againist the mycoparasitic invasion

P347 - Most fungal pathogens secrete effector molecules that function as virulence factors to facilitate disease on hosts, but they are also recognized by cognate plant resistance proteins to arrest fungal growth. Ten effector genes identified in leaf mold pathogen Cladosporium fulvum are strongly up-regulated during infection of the host plant tomato, but not or hardly in vitro. The fungal mycoparasite Dicyma puvinata is a well-known biocontrol agent that parasitizes several fungal leaf pathogens including C. fulvum. We found that in C. fulvum expression of most effector genes is up-regulated when it is co-cultured with D. puvinata. In addition, C. fulvum ¿ Avr4 and ¿Ecp6 deletion mutants are more susceptible to D. pulvinata than wild-type strain, suggesting that these effectors are not only important for defence of C. fulvum against tomato chitinases during infection but also to defend this fungus against mycoparasitic invasion. Most effectors are species-specific and a few are non-species-specific core effectors like Avr4 and Ecp6. Avr4 protects the C. fulvum cell wall from hydrolysis by tomato chitinase directly through chitin binding, whereas Ecp6 scavenges chitin fragments in the apoplastic region to prevent chitin-mediated elicitation of immune responses. These results suggest that chitinases from D. pulvinata are important for mycoparasitism, and C.fulvum deploys the same effectors to protect itself against both plants and mycoparasites.