Metabolomics analysis of mycelial exudates provides insights into fungal antagonists of <i>Armillaria</i>

The genus <i>Armillaria</i> has high edible and medical values, with zones of antagonism often occurring when different species are paired in culture on agar media, while the antagonism-induced metabolic alteration remains unclear. Here, the metabolome of mycelial exudates of two Chinese <i>Armillaria</i> biological species, C and G, co-cultured or cultured separately was analysed to discover the candidate biomarkers and the key metabolic pathways involved in <i>Armillaria</i> antagonists. A total of 2,377 metabolites were identified, mainly organic acids and derivatives, lipids and lipid-like molecules, and organoheterocyclic compounds. There were 248 and 142 differentially expressed metabolites between group C-G and C, C-G, and G, respectively, and fourteen common differentially expressed metabolites including malate, uracil, Leu-Gln-Arg, etc. Metabolic pathways like TCA cycle and pyrimidine metabolism were significantly affected by C-G co-culture. Additionally, 156 new metabolites (largely organic acids and derivatives) including 32 potential antifungal compounds, primarily enriched into biosynthesis of secondary metabolites pathways were identified in C-G co-culture mode. We concluded that malate and uracil could be used as the candidate biomarkers, and TCA cycle and pyrimidine metabolism were the key metabolic pathways involved in <i>Armillaria</i> antagonists. The metabolic changes revealed in this study provide insights into the mechanisms underlying fungal antagonists.