INDUCED DEFENSE RESPONSES IN COTTON LEAF-DISKS BY ELICITORS FROM VERTICILLIUM-DAHLIAE

Cotton (Gossypium hirsutum) leaf tissue responded with symptoms of chl orosis and necrosis to treatment with heat-released soluble cell-wall fragments from Verticillium dahliae. The induction of defence response s in leaf disks by the elicitor led to increased synthesis of anti-fun gal lasinilene and cadalene stress metabolites, as well as the rapid d eposition of phenolic polymers in the lignin fraction. The coordinated induction and accumulation of chitinases and 1,3-beta-glucanases were observed following elicitation; selective low pH extracts of pathogen esis related-proteins revealed a bi-phasic defence hydrolase response that reached a peak within 12 hr, followed by a gradual increase up to 120 hr. Electrophoretic analysis and enzyme staining revealed differe nces in constitutive and inducible proteins. Three acidic isozymes of chitinase with isoelectric points in the range 3.7-4.2, but only one b eta-1,3-glucanase isozyme with an isoelectric point of 4.5 were found in the intercellular fluid. The results obtained indicate that the eli citation of cotton leaf disks by V. dahliae derived signal molecules e xhibits some properties of a multicomponent dynamic system where diffe rent protective mechanisms have complementary roles in the overall exp ression of the defence response. Copyright (C) 1997 Elsevier Science L td.