FUSARIUM-SOLANI DNASE IS A SIGNAL FOR INCREASING EXPRESSION OF NONHOST DISEASE RESISTANCE RESPONSE GENES, HYPERSENSITIVITY, AND PISATIN PRODUCTION

The inoculation of pea endocarp tissue with the bean pathogen Fusarium solani f. sp, phaseoli results in a non-host resistance response caus ing a complete cessation of fungal growth within 6 to 8 h, In addition to previously reported elicitation by chitosan, we now report that co mponents Of this response are also induced by a DNase released from th is fungus, A single band of protein corresponding with DNase activity elicits phytoalexin production and the accumulation of RNA homologous with the pathogenesis-related (PR) genes DRR49, DRR206, and DRR230, Bo th the enzyme activity and the eliciting potential of the Fusarium DNa se (Fsp DNase) are heat stable but susceptible to digestion by protein ase K. Fsp DNase mimics the intact fungus in inducing resistance again st F. solani f. sp. pisi. Also, Fsp DNase causes similar cytologically detectable changes in pea tissue, such as increasing hypersensitive d iscoloration and diminishing fluorescence of Hoechst 33342-stained nuc lei and fluorescein diacetate stained cells.