Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/28/2012
Publication Date: 1/13/2013
Publication URL: http://handle.nal.usda.gov/10113/58547
Citation: Hadwiger, L.A., Polashock, J.J. 2013. Fungal mitochondrial DNases: Effectors with the potential to activate plant defenses in nonhost resistance. Phytopathology. 103:81-90. Interpretive Summary: Plants are resistant to most potential disease-causing organisms. The mechanism(s) of resistance are not completely understood. We propose that one mechanism of this resistance is triggered by specific proteins made by the potential pathogens. We further propose that the resistance triggered by this mechanism induces a response in the plant that protects them from being infected by other disease-causing organisms. To support this idea, we chose to study the response of common garden pea to brewer’s yeast. We demonstrate that a yeast protein causes the plant to produce other proteins that are often produced when the plant is infected by pathogens and induces resistance to other organisms that normally cause disease in pea. Plants engineered to express these specific proteins from microorganisms may be resistant to many pathogens. This information will be useful to research scientists working on various aspects of plant defenses against pathogens.
Technical Abstract: Previous reports on the model nonhost resistance interaction between Fusarium solani f. sp. phaseoli (Fsph) and pea endocarp tissue, have described the signaling role of a fungal DNase1-like protein. This enzyme termed, FsphDNase, induced complete resistance in pea tissue against pea pathogens, no further growth occurred beyond germination. This FsphDNase gene when transferred to tobacco generated resistance against Pseudomonas syringe pv. tabaci. The current analytical/theoretical paper proposes similar roles for the additional nuclear and mitochondrial nuclease genes currently being identified in newly available fungal sequences. Amino acid sequence homologies of these nucleases range from highly-conserved to moderately-conserved within a wide array of fungi. Yeast DNase homology is divergent from Verticillium dahliae and was selected to demonstrate that this saprophyte and its DNase can also elicit nonhost defense responses in pea including pisatin accumulation, PR gene induction, and resistance against a true pea pathogen. The yeast mitochondrial DNase gene (ORF) predictably codes a signal peptide providing the mechanism for secretion.