THE PLANT CELL, Vol 1, Issue 12 1209-1221, Copyright © 1989 by American Society of Plant Biologists
Immunogold Localization of [beta]-1,3-Glucanases in Two Plants Infected by Vascular Wilt Fungi
N. Benhamou, J. Grenier, A. Asselin and M. Legrand
Departement de Phytologie, Faculte des Sciences de L'Agriculture et de L'Alimentation, Universite Laval, Sainte-Foy, Quebec, G1K 7P4, Canada
An antiserum raised against a purified tobacco [beta]-1,3-glucanase (PR-N)
was used to study the subcellular localization of enzyme in fungus-infected
plant tissues by means of post-embedding immunogold labeling. In
susceptible tomato plants, the enzyme accumulation was found to occur as a
result of successful tissue colonization, whereas it appeared to be an
early event associated with limited spread of the fungus in resistant
tissues. Although marked differences between susceptible and resistant
tomato cultivars were observed in the rate of production of
[beta]-1,3-glucanase, the pattern of enzyme distribution was similar. The
enzyme was found to accumulate predominantly in host cell walls and
secondary thickenings of xylem vessels. By contrast, a very low amount of
enzyme was associated with compound middle lamellae. The occurrence of
[beta]-1,3-glucanase at the cell surface of invading fungi was an
indication of their possible antifungal activity. A low enzyme
concentration was detected in vacuoles of both healthy and infected
tissues. In infected eggplant tissue, the pattern of [beta]-1,3-glucanase
distribution was similar to that observed with tomato. Whether these
hydrolases accumulate first in vacuoles and are subsequently conveyed
toward the outside to participate in fungal wall lysis remains to be
determined.
