Figure 2.

Spruce stilbene glucosides are metabolized by spruce tree—and bark beetle—associated fungi. (a and b) Representative images of spruce tree–associated fungi (C. radians, B. nummularia, and H. annosum) (a) and bark beetle (I. Typographus)–associated fungi (Cylindrobasidium ipidophilum, Endoconidiophora polonica, and Grosmannia penicillata) (b) grown on SB-PDA. (c and d) Volcano plots illustrate features (m/z value, retention time in min) derived from untargeted UHPLC–qTOF–MS analyses of spruce tree–associated fungi (c) and I. typographus–associated fungi (d) incubated on SB-PDA medium compared with uninoculated medium in the negative mode (n = 5). (e–g) Volcano plots illustrate features (m/z value, retention time in min) derived from untargeted UHPLC–qTOF–MS analyses of fungi C. radians (e) and C. ipidophilum (f) on PDA supplemented with unlabeled resveratrol versus [¹³C₆] resveratrol (labeled in the monohydroxylated ring) in the negative mode (n = 4–5), as well as C. radians (g) in the positive mode (n = 5). Features are presented as peak intensities normalized to sample weight and log₁₀-transformed. Compounds were subsequently identified by comparison of mass spectra and retention times to those of authentic standards. The piceatannol dimer is langusol C, and the resveratrol dimers are E-δ-viniferin and Z-δ-viniferin. E-1a and Z-1a denote the E- and Z-isomers, respectively. Detailed metabolomic results are provided in the raw data file, and representative mass spectra of phenolic compounds and authentic standards are shown in Supplementary File 2. Statistical significance between groups was assessed using two-tailed t-tests (P < .05) in c–g.