HOST PATHOGEN INTERACTIONS .37. ABILITIES OF THE POLYGALACTURONASE-INHIBITING PROTEINS FROM 4 CULTIVARS OF PHASEOLUS-VULGARIS TO INHIBIT THE ENDOPOLYGALACTURONASES FROM 3 RACES OF COLLETOTRICHUM-LINDEMUTHIANUM

The ability of endopolygalacturonases isolated from three races of Colletotrichum lindemuthianum to form phytoalexin elicitor-active oligogalacturonides was studied in the absence and presence of endopolygalacturonase-inhibiting proteins (PGIPs) isolated from four varieties of Phaseolus vulgaris. Endopolygalacturonases (each 40 kDa on SDS-PAGE) from the α, β, and γ races of Colletotrichum lindemuthianum were purified by ion-exchange and fast-protein-liquid gel-permeation chromatographies. The polygalacturonases from the three races formed elicitor-active oligogalacturonides at the same rate. PGIPs (each 41 kDa) were purified from four different cultivars of Phaseolus vulgaris (cvs Great Northern, Pinto, Red Kidney, and Small Red) by affinity chromatography through a Sepharose-endopolygalacturonase column. The PGIPs from all four cvs of P. vulgaris were able to increase the lifetimes of phytoalexin elicitor-active oligogalacturonides generated by the endopolygalacturonases. We observed no significant differences in the rate and pattern of formation of elicitor-active oligogalacturonides by the three enzymes in the presence of each of the four PGIPs. Our data indicate that the interaction between endopolygalacturonases and their inhibitor proteins does not per se explain race-cultivar specificity. © 1990.