Fusarium solani DNase Is a Signal for Increasing Expression of Nonhost Disease Resistance Response Genes, Hypersensitivity, and Pisatin Production. Lee A. Hadwiger . Department of Plant Pathology, Washington State University, Pullman, WA 99164 U.S.A. Ming-Mei Chang (2), and M. Angela Parsons (3). (2) Department of t Biology, State University New York, Geneseo 14454 U.S.A. (3) Current address: Institute of Biosciences and Technology, Texas A&M University, Texas Medical Center, Houston 77030 U.S.A. MPMI 8:871-879. Accepted 27 July 1995. Copyright 1995 The American Phytopathological Society.

The inoculation of pea endocarp tissue with the bean pathogen Fusarium solani f. sp. phaseoli results in a nonhost resistance response causing a complete cessation of fungal growth within 6 to 8 h. In addition to previously reported elicitation by chitosan, we now report that components of this response are also induced by a DNase released from this 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. Both the enzyme activity and the eliciting potential of the Fusarium DNase (Fsp DNase) are heat stable but susceptible to digestion by proteinase K. Fsp DNase mimics the intact fungus in inducing resistance against F. solani f. sp. pisi. Also, Fsp DNase causes similar cytologi-cally detectable changes in pea tissue, such as increasing hypersensitive discoloration and diminishing fluorescence of Hoechst 33342-stained nuclei and fluorescein diacetate stained cells.