Submitted to: International Aphanomyces Symposium
Publication Type: Proceedings
Publication Acceptance Date: July 25, 2003
Publication Date: November 3, 2003
Citation: WEILAND, J.J. HOST-PATHOGEN INTERATIONS IN THE PHYTOPATHOGENIC APHANOMYCES. PROCEEDINGS 2ND International Aphanomyces Symposium. 2003. P.43-49. Interpretive Summary: Understanding the mechanisms used by plant pathogens to gain entry in to crop plants enables us to design the means to prevent crop infection. Enzymes produced by fungi that digest the exterior of the plant are candidate targets for the focus of anti-fungal strategies. An enzyme activity, protease, was found to be produced by Aphanomyces cochlioides, a fungus that causes root rot of sugarbeet with high economic impact. The protease enzyme was found in infected plants and in laboratory cultures of the fungus. Use of chemical probes enabled preliminary characterization of the protease to be made. This information could be used to screen sugarbeet germplasm for varieties that possess improved resistance to root rot via the production of protease inhibitors.
Technical Abstract: Bulk assay and gel activity assays were used to characterize proteases secreted by Aphanomyces cochlioides and A. euteiches both in culture and in infected seedlings. Using bulk assays, inhibitors of trypsin-like enzymes were capable of reducing sample protease activity, whereas inhibitors for other protease classes had no effect. Non-denaturing sodium dodecylsulfate polyacrylamide gel electrophoresis separated protease isozymes secreted by A. cochlioides into 7-8 resolvable bands whereas those secreted by A. euteiches were resolved into 6 bands. Incorporation of trypsin-class inhibitors either into the electrophoresis gels or into the activity staining buffer resulted in a decrease of activity for the fastest migrating isozymes. The involvement of protease activity in the infection of plants by Aphanomyces and the implications for disease control are discussed.