Pathogen-induced vascular gels: Ethylene as a host intermediate

A cell free culture filtrate from 6-day cultures of Fusarium oxysporum f. sp. cubense was processed to give: (1) a heterogeneous enzyme mixture, (2) purified polygalacturonase (PG), (3) partially-purified polygalacturonate lyase and (4) β-1,4-xylanase. When introduced into explanted castor bean leaves each of these preparations was able to promote the formation of vascular system-obstructing gels. Exposure of castor bean leaves to ethylene (3 ppm) also triggered gel formation. Explanted leaves produced ethylene in response to the enzyme mixture and PG. Vascular gel formation did not occur when ethylene production in response to enzymes was prevented.