Similar to plants, fungi - in particular the fruiting bodies (sporocarps) of higher fungi (macrofungi) - are potential victims of attack by fungivores and microorganisms. The fruiting bodies of mushrooms turned out to be a rich source of secondary metabolites with unusual structures. Although the ecological role of many of these natural products is mostly still obscure, at least several of them have been established to serve defense purposes.
Upon injury, that is, attack, many fruiting bodies react with a change of their color, exhibit a bitter or pungent taste, and emit the typical mushroom scent of (35)-1-octen-3-ol. This compound is derived by action of 11-lipoxygenase on linoleic acid. The generated (8E,12Z,10S)-10-hydroper-oxy-8,12-octadecadienoic acid is cleaved and produces, besides (3R)-1-octen-3-ol, (8E)-10-oxo-8-decenoic acid as the counterpart. In analogy to plant signaling processes, polyunsaturated fatty acid-derived compounds may serve as signals to upregulate defense reactions (see Plant Defense).
Besides such a possible induced defense, mushrooms use constitutively produced defense compounds. In addition, defense compounds are often stored as inactive precursors that are converted to toxic compounds upon attack (activated defense).
In this article, we present some illustrative examples of fungal defense strategies drawing parallels to other organisms as well as present the defensive potential of unique compounds that are typical for fungal secondary metabolites.
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