hide
Free keywords:
-
Abstract:
Norway spruce (Picea abies) forests suffer periodic fatal attacks by the bark
beetle Ips typographus and its fungal associate, Ceratocystis polonica. P. abies protects
itself against fungal and bark beetle invasion by production of terpenoid resins, but it is
unclear whether resins or other defenses are effective against the fungus. We investigated
stilbenes, a group of phenolic compounds found in P. abies bark with a diaryl-ethene
skeleton with known antifungal properties. During C. polonica infection, stilbene
biosynthesis was up-regulated as evidenced by elevated transcript levels of stilbene
synthase genes. However, stilbene concentrations actually declined during infection and
this was due to fungal metabolism. C. polonica converted stilbenes to ring-opened,
deglycosylated and dimeric products. Chromatographic separation of C. polonica protein
extracts confirmed that these metabolites arose from specific fungal enzyme activities.
Comparison of C. polonica strains showed that rapid conversion of host phenolics is
associated with higher virulence. C. polonica is so well adapted to its host’s chemical defenses that it is even able to use host phenolic compounds as its sole carbon source.
