A PHYTOTOXIC PROTEIN-LIPOPOLYSACCHARIDE COMPLEX PRODUCED BY VERTICILLIUM-DAHLIAE

A phytotoxic protein-lipopolysaccharide complex (PLPC) was purified to electrophoretic homogenetiy from seven-day-old culture filtrates of V erticillium dahliae by means of acetone precipitation, gel exclusion c hromatography, and preparative agarose electrophoresis with a yield of 4.5 mgl(-1) culture filtrate. The PLPC consists of 15.7% protein, 13. 0% lipid, 0.4% phosphate and 70% carbohydrate. The isoelectric point i s 3.8 and the amino acid composition of the protein fraction was deter mined. The complex has a M(r) of 197000 and can be dissociated into fi ve protein-containing components, with M(r)S of 78000, 62000, 48000, 3 2000 and 28000. Polygalacturonase and cellulase enzyme activities were identified in the PLPC by means of enzyme staining techniques, and we re found to be associated with the 28000 and 48000 M(r) complexes, res pectively. 1,3-beta-Glucanase activity was associated with the 32000 a nd 28000 M(r) complexes. Treatment of cotton seedlings with concentrat ions from 2.5 mu g ml(-1) PLPC resulted in symptoms of wilting and nec rosis and was accompanied by inhibition of the H+-ATPase activity of p lasma membranes and the rapid transient elicitation of phenylalanine a mmonia-lyase activity. Significant differences were found between resi stant and susceptible cultivars. When applied to disks of mature cotto n leaves, the PLPC elicited the accumulation of pathogenesis-related p roteins in the intercellular spaces.