LICHEN METABOLITES INHIBIT CELL WALL-DEGRADING ENZYMES PRODUCED BY THE LICHEN PARASITE NECTRIA-PARMELIAE

We report results of laboratory experiments showing that the cell wall -degrading enzymes of the lichen parasite Nectria parmeliae exhibit se nsitivities to the lichen metabolites of two lichens, Punctelia rudect a and Flavoparmelia baltimorensis, that reflect known differences in t he parasite's ability to degrade these lichens. In the case of P. rude cta, which is apparently well-defended chemically from N. parmeliae, t he activity of wall-degrading polysaccharidases produced by N. parmeli ae was reduced by half in the presence of lichen compounds. In the cas e off. baltimorensis, which is apparently poorly defended, the parasit e's growth and enzyme production were suppressed during the first week on walls containing lichen compounds. However, growth was observed to increase during the second week, at which time no effects of these co mpounds on enzyme activity were evident. These results are significant because: 1) they demonstrate for the first time a correlation between host tissue degradation by a lichen parasite and the activity of wall -degrading enzymes; and 2) they indicate an important role of lichen m etabolites in modulating this degradative ability.