Subcellular localization of beta-glucosidase in rye, maize and wheat seedlings

The subcellular compartmentation of beta -glucosidase was studied in rye, m aize and wheat seedlings by immunocytochemical methods. For detection, we u sed a 10 nm gold-labeled secondary antibody, and results were observed usin g transmission electron microscopy. In all three species, beta -glucosidase was found in plastids, cytoplasm and cell walls. In rye, gold particles we re seen on cell walls and cytoplasm in epidermal cells of the root tip and shoot, in bundle sheath cells of the shoot and in all cells, except the vas cular bundle cells of the coleoptile. Gold labeling was also observed in pl astids of the bundle sheath cells of rye shoot tips and in cortical cells o f root tips. In wheat, gold labeling was observed on cell walls and cytopla sm of epidermal cells in the shoot base and coleoptile, and on cell wails a nd plastids in epidermal cells of the root tip, In maize, gold labeling was mainly found in plastids or proplastids in vascular bundle cells and bundl e sheath cells of the shoot, in bundle sheath cells of the coleoptile and i n epidermal cells of the root. Some gold particles were also found in cell walls and cytoplasm of stomatal guard cells of the shoot base and vascular bundle cells of the shoot tip and in the cell walls of bundle sheath cells of the shoot tip and root tip epidermal cells. Results are discussed in rel ation to the role of beta -glucosidase in hydroxamic acid release and overa ll defense mechanism of monocotyledons.