Cerato platanins (CP) of Fusarium graminearum induce defense responses in plant and are not essential for fungal virulence.

Cerato platanins (CP) belong to a family of small secreted fungal proteins with phytotoxic activity which seem to induce defense responses and necrosis in plants and contribute to Botrytis cinerea and Magnaporthe grisea virulence. In the genome of F. graminearum, a necrotrophic fungal pathogen which causes Fusarium head blight (FHB) disease of wheat, barley and other cereal grains, there are two genes (FGSG_10212 and FGSG_11205) putatively encoding for CP-like proteins that we cloned and heterologously expressed in Pichia pastoris. The recombinant proteins, native and boiled, resulted able to reduce the viscosity of carboxymethyl cellulose, in particular the FgCP11205. Treatments of Arabidopsis thaliana leaves with the two F. graminearum CPs induced necrotic symptoms, accumulation of H2O2 and expression of defense genes, specifically PR1, marker of salicylic acid signaling, and ERF1b, a transcriptional regulator of some ethylene-responsive genes. Being these CPs able to induce defense responses, we tested their effectiveness in increasing the resistance of A. thaliana to the fungal pathogen B. cinerea; treatments with both CPs determined a reduction of lesion size of about 30-40%. The expression of the two cp genes was analyzed by qPCR in the early stages of wheat spike infection and during in vitro growth and only the Fgcp10212 gene resulted strongly transcribed. To verify the contribution of F. graminearum CPs to fungal virulence, single and double gene knock-out mutants were produced and used to infect host plants such as wheat and soybean but their virulence resulted comparable to that of the wild-type strain.