Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
Department of Biology, Lund University, Lund, Sweden.
ISME J. 2019 Jul;13(7):1788-1800. doi: 10.1038/s41396-019-0390-3. Epub 2019 Mar 14.
Insects have mutualistic symbioses with a variety of microorganisms. However, the chemical signals that maintain these insect-microbe relationships are poorly known compared to those from insect-plant symbioses. The spruce bark beetle, Ips typographus, the most destructive forest pest in Europe, has a symbiotic relationship with several fungi that are believed to contribute to its successful invasion of Norway spruce. Here we tested the hypothesis that volatile organic compounds (VOCs) emitted from fungal symbionts could be cues for bark beetles to recognize and distinguish among members of its microbial community. Behavioral experiments with fungi showed that immature adults of I. typographus are attracted to food sources colonized by their fungal symbionts but not to saprophytic fungi and that this attraction is mediated by volatile cues. GC-MS measurements revealed that the symbionts emitted VOCs. Testing the activity of these compounds on beetle antennae using single sensillum recordings showed that beetles detect many fungal volatiles and possess olfactory sensory neurons specialized for these compounds. Finally, synthetic blends of fungal volatiles attracted beetles in olfactometer experiments. These findings indicate that volatile compounds produced by fungi may act as recognition signals for bark beetles to maintain specific microbial communities that might have impact on their fitness.
昆虫与各种微生物存在互利共生关系。然而，与昆虫-植物共生关系相比，维持这些昆虫-微生物关系的化学信号知之甚少。云杉树皮甲虫 Ips typographus 是欧洲最具破坏性的森林害虫，它与几种真菌存在共生关系，这些真菌被认为有助于其成功入侵挪威云杉。在这里，我们检验了这样一个假设，即真菌共生体释放的挥发性有机化合物 (VOC) 可能是树皮甲虫识别和区分其微生物群落成员的线索。用真菌进行的行为实验表明，不成熟的 Ips typographus 成虫被它们的真菌共生体定植的食物源所吸引，但不会被腐生真菌吸引，这种吸引力是由挥发性线索介导的。GC-MS 测量表明，共生体释放 VOC。使用单感器记录测试这些化合物在甲虫触角上的活性表明，甲虫可以检测到许多真菌挥发物，并拥有专门针对这些化合物的嗅觉感觉神经元。最后，真菌挥发物的合成混合物在嗅觉计实验中吸引了甲虫。这些发现表明，真菌产生的挥发性化合物可能作为树皮甲虫维持特定微生物群落的识别信号，这可能对它们的适应性产生影响。
