Lichen metabolites inhibit cell wall-degrading enzymes produced by the lichen parasite Nectria parmeliae

Abstract

We report results of laboratory experiments showing that the cell wall-degrading enzymes of the lichen parasite Nectria parmeliae exhibit sensitivities to the lichen metabolites of two lichens, Punctelia rudecta and Flavoparmelia baltimorensis, that reflect known differences in the parasite's ability to degrade these lichens. In the case of P. rudecta, which is apparently well-defended chemically from N. parmeliae, the activity of wall-degrading polysaccharidases produced by N. parmeliae was reduced by half in the presence of lichen compounds. In the case of F. baltimorensis, which is apparently poorly defended, the parasite'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 compounds 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 metabolites in modulating this degradative ability.

Key Words:

• allelochemicals
• host-parasite interactions
• Hypocreales
• lichenicolous fungi
• lichens
• Nectria parmeliae
• wall-degrading polysaccharidases