A Case of Plant Vaccination: Enhancement of Plant Immunity against Verticillium dahliae by Necrotized Spores of the Pathogen.

The soil-borne fungus Verticillium dahliae is causing a devastating vascular disease in more than 200 species of dicotyledonous plants. The pathogen attacks susceptible plants through the roots, colonizes the plant vascular system, and causes the death of aerial tissues. In this study, we used Arabidopsis and eggplants to examine the plant protective and immunization effects of autoclaved V. dahliae spores against V. dahliae . We observed that the application of V. dahliae autoclaved spores in eggplants and Arabidopsis resulted in enhanced protection against V. dahliae , since the disease severity and pathogen colonization were lower in the plants treated with V. dahliae autoclaved spores when compared to controls. In addition, upregulation of the defense related genes PR1 and PDF1.2 in the Arabidopsis plants treated with the V. dahliae autoclaved spores was revealed. Furthermore, pathogenicity experiments in the Arabidopsis mutant cerk1 , defective in chitin perception, revealed a loss of protection against V. dahliae in the cerk1 treated with the V. dahliae autoclaved spores. The participation of the chitin receptor CERK1 is evident in Arabidopsis immunization against V. dahliae using autoclaved spores of the pathogen.