A new endophytic insect-associated Daldinia species, recognised from a comparison of secondary metabolite profiles and molecular phylogeny

Abstract

Xylariaceous endophytes are commonly encountered in plants, and it has recently been found out that insect vectors play a major role in their life cycle, as well as in the apparent host-specificity of the fungal stromata. In this study, a new insect-associated, endophytic anamorph species of Daldinia is recognised from a comparison of a) morphological and ecological data; b) molecular phylogenetic data based on rDNA, alpha-actin and beta-tubulin genes; and c) secondary metabolite profiles based on high performance liquid chromatography/diode array/mass spectrometry (HPLC-DAD/MS) and gas chromatography/mass spectrometry (GC-MS) in comparison with authentic strains of Daldinia and other Xylariaceae. The new species, Daldinia hawksworthii, is a symbiont of the willow woodwasp, Xiphydria prolongata, which is in turn preferentially associated with Salix. A comparison of HPLC-DAD/MS profiles from standardised cultures revealed the presence of a specific compound, which was not encountered in any of the ca. 250 Daldinia strains studied for comparison. This compound was isolated after fermentation of the fungus in 10 l scale by preparative chromatography. Structure elucidation by NMR spectroscopy revealed a novel pyrone, for which the name dalsymbiopyrone is proposed. The compound showed weak antimicrobial and cytotoxic effects and might be a signal molecule involved in the trilateral ecological interaction between the host plant, the insect, and its fungal symbiont.