Localization of vicilin peptidohydrolase in the cotyledons of mung bean seedlings by immunofluorescence microscopy

Vicilin peptidohydrolase, the protease that hydrolyzes the reserve proteins in the cotyledons of mung bean (Vigna radiata) seedlings, has been localized intracellularly by immunofluorescence microscopy using monospecific antibodies against the enzyme and rhodamine-coupled goat- anti-rabbit immunoglobulin G's. The enzyme can first be visualized after 3 days of seedling growth and is associated with small foci within the cytoplasm of the storage parenchyma cells farthest from the vascular bundles. On the 4th day of growth, the protease is also present in the numerous large protein bodies within these cells. Vicilin peptidohydrolase is known to be synthesized de novo starting on the 3rd day of growth. Our observations are therefore consistent with the interpretation that the enzyme is synthesized in the cytoplasm and subsequently transported to the protein bodies.