THE EFFECT OF INHIBITORS OF VARIOUS CELLULAR PROCESSES ON THE WALL MODIFICATIONS INDUCED IN BEAN-LEAVES BY THE COWPEA RUST FUNGUS

The effects of inhibitors of cellular processes on the modifications of mesophyll cell walls induced in bean leaves by the cowpea rust fungus were determined. Inhibitors of glycoprotein processing in the endoplasmic reticulum inhibited the deposition of callose, silica, and wall-bound autofluorescent materials thought to be phenolic in nature. Inhibitors of Golgi function had no effect. Anti-microtubule agents inhibited only silica deposition, as did the hydroxylation inhibitor, α,α′-dipyridyl. Anti-microfilament agents and inhibitors of phenylpropanoid synthesis inhibited both silica deposition and wall autofluorescence. The data support the previous conclusion that callose deposition is metabolically independent of the other two wall modifications. The data also suggest that wall autofluorescence is independent of silica deposition, but the latter requires the presence of phenolic compounds and, possibly, hydroxyproline-rich glycoproteins in the plant cell wall. All tested inhibitors of a given cellular process or structure had the same range of effects on wall modifications. However, a reduced incidence in all three wall modifications did not necessarily result in an increase in the incidence of fungal haustoria (which are not normally formed in this interaction), possibly because some inhibitors may have adversely affected fungal growth. The data suggest, however, that silica deposition, may be the most important of the three responses in preventing haustorium formation in normal plants. © 1991 Academic Press Limited.