β-Glucosidases as detonators of plant chemical defense

Abstract

Some plant secondary metabolites are classified as phytoanticipins. When plant tissue in which they are present is disrupted, the phytoanticipins are bio-activated by the action of β-glucosidases. These binary systems – two sets of components that when separated are relatively inert – provide plants with an immediate chemical defense against protruding herbivores and pathogens. This review provides an update on our knowledge of the β-glucosidases involved in activation of the four major classes of phytoanticipins: cyanogenic glucosides, benzoxazinoid glucosides, avenacosides and glucosinolates. New aspects of the role of specific proteins that either control oligomerization of the β-glucosidases or modulate their product specificity are discussed in an evolutionary perspective.