Nuclease released by Verticillium dahliae is a signal for non-host resistance

A DNase released from the fungal pathogen of bean, Fusarium solani f. sp. phaseoli (Fsph), was previously shown to signal the activation of total disease resistance and activate pathogenesis-related (PR) genes in pea. Data in the current study which used the pea-endocarp model to research non-host resistance, indicated that DNase released by Verticillium dahliae (Vd), pathogenic on potato also has non-host resistance-inducing capabilities in peas. Other strains of Vd that release DNase are pathogenic on other plant species. DNase catalytic activity was also released from representative genera of other pathogenic fungi. Purified VdDNase induced pisatin and pea gene DRR49 (PR-10 gene) in pea endocarp tissue. VdDNase reduced the in vitro growth of Vd but completely inhibited that of F. solani f. sp. pisi (Fspi) and a Colletotrichum pathogen of potato. VdDNase (2 units) applied to pea endocarp tissue both broke resistance to Fsph and increased resistance to Fspi. Pea DNA damage generated both by the VdDNase enzyme and the intact Vd spores indicated that the host DNA alteration is a component of the non-host resistance response (innate immunity). These data support the previously reported inductive potential of fungal DNase and further implicate fungal DNases as signals in activating non-host resistance responses.