Binding of the phytotoxin zinniol stimulates the entry of calcium into plant protoplasts.
Zinniol [1,2-bis(hydroxymethyl)-3-methoxy-4-methyl-5-(3-methyl-2-butenyloxy)benzene], a toxin produced by fungi of the Alternaria group, causes symptoms in plants that resemble those induced by the fungi. The phytotoxin binds to carrot protoplasts and isolated membranes in a saturable and reversible manner. Receptor occupancy stimulates entry of calcium into protoplasts. Zinniol can partially reverse the effects and binding of the calcium-channel blockers desmethoxyverapamil and bepridil. Selected cell lines that are insensitive to zinniol lose part of their binding capacity and sensitivity to the action of the agonist-like compound but are still able to bind calcium-channel blockers. We conclude that zinniol acts on calcium entry but that the targets of the toxin and of calcium-channel blockers are dissimilar, suggesting the occurrence of sites affected both by zinniol and by channel blockers and of sites affected only by zinniol.
Thuleau
P
P
Centre de Physiologie Végétale, Université Paul Sabatier, Centre National de la Recherche Scientifique Unité Associée 241, 118 route de Narbonne, F-31062 Toulouse Cédex, France.
Graziana
A
A
Rossignol
M
M
Kauss
H
H
Auriol
P
P
Ranjeva
R
R