Phenotypic plasticity of cyanogenesis in lima bean Phaseolus lunatus-activity and activation of beta-glucosidase.
Cyanogenesis, the release of toxic HCN from damaged plant tissues, is generally considered as a constitutive plant defense. We found phenotypic plasticity of cyanogenesis in young leaves of lima bean Phaseolus lunatus based on increased activity of the beta-glucosidase in response to herbivore attack. Two aspects of plant cyanogenesis have to be considered in ecological analyses: (1) the cyanogenic potential (HCNp), which indicates the total amount of cyanide-containing compounds present in a given tissue, and (2) the cyanogenic capacity (HCNc), representing the release of HCN per unit time. This release is catalyzed by specific beta-glucosidases, whose activity is a crucial parameter determining overall toxicity. Enzymatic activity of beta-glucosidase-and, in consequence, the rate of HCN release-was increased significantly after 72 hr of incubation with spider mites as compared to non-infested leaves. Feeding by L1 larvae of Mexican bean beetles also led to enhanced enzymatic activity, whereas mechanical damage of leaf tissue had no effect on beta-glucosidase activity and the release of HCN. The results place plant cyanogenesis in the group of induced resistance traits, whose degree of activity depends on the feeding by a particular herbivore.
Department of Botany, University of Duisburg-Essen, Universitätsstr. 5, 45117 Essen, Germany. daniel.ballhorn@uni-due.de
Daniel J
DJ
Ballhorn
Martin
M
Heil
Reinhard
R
Lieberei
D000818:Animals; D001517:Coleoptera / Q000502:physiology; D005260:Female; D005838:Genotype; D006790:Host-Parasite Interactions; D006856:Hydrogen Cyanide / Q000032:analysis / Q000378:metabolism*; D027805:Phaseolus / Q000378:metabolism* / Q000469:parasitology; D010641:Phenotype; D010675:Pheromones / Q000032:analysis / Q000096:biosynthesis; D018515:Plant Leaves / Q000378:metabolism* / Q000469:parasitology; D040102:Tetranychidae / Q000502:physiology; D001617:beta-Glucosidase / Q000032:analysis / Q000378:metabolism*
D010675:Pheromones; D006856:Hydrogen Cyanide; D001617:beta-Glucosidase