Volatile sesquiterpenes from fungi: what are they good for?

Fungi can be found in almost all sorts of habitats competing with an even higher number of other organisms. As a consequence fungi developed a number of strategies for protection and communication with other organisms. This review focuses on the increasing number of volatile sesquiterpenes found to be produced by fungal species. The remarkable diversity of this type of volatile organic compound (VOC) within the kingdom fungi is presented and their benefits for the fungi are discussed. The majority of these compounds are hydrocarbons comprising several dozens of carbon skeletons. Together with oxygenated sesquiterpenes they include compounds unique to fungi. Only in recent years the interest shifted from a mere detection and characterization of compounds to their biological function. This review reveals highly diverse ecological functions including interactions with bacteria, other fungi, insects and plants. VOCs act as autoinducer, defend against competing species and play essential roles in attracting pollinators for spreading fungal spores. For many sesquiterpene VOCs sophisticated responses in other organisms have been identified. Some of these interactions are complex involving several partners or transformation of the emitted sesquiterpene. A detailed description of ecological functions of selected sesquiterpenes is given as well as their potential application as marker molecules for detection of mould species. Structures of all described sesquiterpenes are given in the review and the biosynthetic routes of the most common skeletons are presented. Summarizing, this article provides a detailed overview over the current knowledge on fungal sesquiterpene VOCs and gives an outlook on the future developments.