VIEW ARTICLE

Biochemistry and Cell Biology

Evidence for a New Class of Peptide Elicitor of the Hypersensitive Reaction from the Tomato Pathogen Pseudomonas corrugata. D. L. Gustine, United States Department of Agriculture, Agricultural Research Service, Pasture Systems and Watershed Management Research Laboratory, U.S. Regional Pasture Research Laboratory, University Park, PA 16802; R. T. Sherwood, and B. G. Moyer. United States Department of Agriculture, Agricultural Research Service, Pasture Systems and Watershed Management Research Laboratory, U.S. Regional Pasture Research Laboratory, University Park, PA 16802. Phytopathology 85:848-853. Accepted for publication 25 April 1995. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1995. DOI: 10.1094/Phyto-85-848.

Three elicitor-active fractions were isolated from culture fluids of the rough isolate of Pseudomonas corrugata, a tomato pathogen that elicits the hypersensitive reaction (HR) in tobacco. Lyophilized, filtered culture fluids were extracted with methanol-ethyl acetate (80:20, vol/vol) to produce a water-soluble crude extract (CE). CE was partitioned with ethyl acetate to produce water-soluble aqueous (AQ) and organic (EA) fractions containing purified elicitor. P. corrugata and the three fractions were tested for their ability to elicit HR in tobacco leaves, pith necrosis in tomato, and K⁺/H⁺ exchange in tobacco tissue culture. Only P. corrugata elicited pith necrosis in tomato; both bacteria and the fractions elicited HR in tobacco leaves; and bacteria and EA elicited K⁺/H⁺ exchange in tobacco cells. The primary component in EA, HR2, did not cause a spreading lesion in tobacco and was therefore not a toxin. HR2 was found to be 95% pure by analytical high-performance liquid chromatography, to contain a fluorescent chromophore, and to be a peptide. HR2 contains glutamic acid, tyrosine, aspartic acid, glycine, alanine and/or arginine, isoleucine and/or leucine, and methionine and/or valine (approximate molar ratio 10:3:1:1:1:1:1). Since P. corrugata is a useful biocontrol agent, these elicitors may have potential use in biocontrol.