BARLEY PATHOGENESIS-RELATED PROTEINS WITH FUNGAL CELL-WALL LYTIC ACTIVITY INHIBIT THE GROWTH OF YEASTS

Proteins from intercellular fluid extracts of chemically stressed barl ey (Hordeum vulgare L.) leaves were separated by native polyacrylamide gel electrophoresis at alkaline or acid pH. Polyacrylamide gels conta ined Saccharomyces cerevisiae (bakers' yeast) or Schizosaccharomyces p ombe (fission yeast) crude cell walls for assaying yeast wall lysis. I n parallel, gels were overlaid with a suspension of yeasts for assayin g growth inhibition by pathogenesis-related proteins. The same assays were also performed with proteins separated by sodium dodecyl sulfate- polyacrylamide gel electrophoresis under nonreducing conditions. In al kaline native polyacrylamide gels, only one band corresponding to yeas t cell wall lytic activity was found to be inhibitory to bakers' yeast growth, whereas in acidic native polyacrylamide gels one band inhibit ed the growth of both yeasts. Under denaturing nonreducing conditions, one band of 19 kD inhibited the growth of both fungi. The 19-kD band corresponded to a basic protein after two-dimensional gel analysis. Th e 19-kD protein with yeast cell wall lytic activity and inhibitory to both yeasts was found to be different from previously reported barley chitosanases that were lytic to fungal spores. It could be different f rom other previously reported lytic antifungal activities related to p athogenesis-related proteins.