Abstract
Norway spruce (Picea abies) forests suffer periodic fatal attacks by the bark beetle Ips typographus and its fungal associate, Ceratocystis polonica. Norway spruce protects itself against fungal and bark beetle invasion by the 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 Norway spruce 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.
Highlights
Norway spruce (Picea abies) forests suffer periodic fatal attacks by the bark beetle Ips typographus and its fungal associate, Ceratocystis polonica
To determine if C. polonica was the agent responsible for the reduced stilbene levels seen in infected bark, isolates 1 and 2 were grown in nutrient broth amended with 2 mg mL21 astringin
After inoculation into Norway spruce by the Eurasian spruce bark beetle (Ips typographus), C. polonica metabolizes the major antifungal phenolic compound produced in the bark
Summary
Norway spruce (Picea abies) forests suffer periodic fatal attacks by the bark beetle Ips typographus and its fungal associate, Ceratocystis polonica. Norway spruce (Picea abies), a dominant tree species in European boreal, montane, and subalpine forests, is frequently subject to fatal attacks by the bark beetle Ips typographus (Wermelinger, 2004) During attacks, these scolytine beetles introduce fungal pathogens into their hosts. Potential antifungal defense compounds may come into contact with necrotrophic fungi It is not yet known how effective Norway spruce defense compounds are against C. polonica and whether this specialized, bark beetle-vectored pathogen has developed any resistance to them. This missing information may be critical in understanding how C. polonica contributes to the success of bark beetle attacks and why so many mutualistic relationships between bark beetles and blue-staining fungi have evolved
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
