The role of effectors, pamps, and secondary metabolites in adaptation of Cladosporium fulvum to tomato

CS-28.1 - The biotrophic tomato pathogen Cladosporium fulvum is a Dothideomycete fungus that is most related to the hemi-biotrophic fungal pine pathogen Dothistroma septosporum. We are interested in understanding genomic adaptations in these and related fungi that can explain host plant-specificity. The C. fulvum genomic sequence allowed us to identify and study its complete effector catalogue of which many effectors had been identified already and of which three represent core effectors (Avr4, Ecp2 and Ecp6) occurring in several genera and species of fungal plant pathogens. The genome of D. septosporum harbors the highest number of homologs of C. fulvum effectors, but some are pseudogenized. Both C. fulvum and D. septosporum contain a large number of genes involved in the production of secondary metabolites. C. fulvum seems to adapt its host plant tomato by down-regulation or pseudogenization of genes involved in the production of toxic secondary metabolites. One clear example is dothiostromin, a toxin produced by D. septosporum during colonization of pine needle. C. fulvum contains all genes required for the production of this toxin, but a few crucial genes have been pseudogenized. Apart from new effectors (Avr5) we have also identified new pathogen-associated molecular patterns (PAMPs), as well as damage-associated molecular patterns (MAMPs) from C. fulvum. Both represent cell-wall degrading enzymes produced by C. fulvum during infection of tomato. We also found that C. fulvum has adapted to grow on tomato by secreting the enzyme a- tomatinase that hydrolyses the antifungal tomato saponin a-tomatine into the non-toxic compounds lycotetraose and tomatidine.