Location of a cell-wall hydroxyproline-rich glycoprotein, cellulose and beta-1,3-glucans in apical and differentiated regions of maize mycorrhizal roots.

The cell-wall components of the interface compartment in functioning mycorrhizal roots of maize (Zea mays L. cv. W64A) have been investigated with the use of immunocytochemistry and enzyme/lectin-gold techniques. The distribution of specific cell-wall probes was determined in the apical and differentiated regions of maize roots in the presence and in the absence of the mycorrhizal fungus, Glomus versiforme. Labelling experiments showed that a maize hydroxyproline-rich glycoprotein (HRGP), identified with a specific antibody, was particularly abundant in the apical dividing cells of the root meristem. Cellulose, located with a cellobiohydrolase-gold complex, showed a similar labelling pattern in the walls of both meristematic and differentiated parts of the roots. When the cortex was colonized by the mycorrhizal fungus, the HRGP and cellulose were expressed in two sites: the wall and the interface area created by invagination of the host membrane around the developing fungus. In contrast, in uninfected roots of the same age, they were only present in the inner part of the wall. A specific antibody against beta-1,3-glucans demonstrated that these glucans were not laid down at the interface between the plant and fungus, while they appeared to be a skeletal component of the fungal wall, together with chitin.