Heterologous Expression of an Abandoned Termite Mound Fungus Gene Cluster Reveals a Protective Aldehyde–Alcohol Cycle and a Candidate Termiticidal Metabolite

The medicinal fungus Wulingshen, comprising multiple Xylaria species, inhabits deserted termite mounds as sclerotia. To explore the molecular basis of its niche adaptation, we employed a synthetic biology-driven approach. Metagenomic and transcriptomic mining of wild specimens identified a conserved biosynthetic gene cluster. Its heterologous reconstruction in the fungal host Aspergillus oryzae enabled the characterization of a family of α-pyrone metabolites and, crucially, the elucidation of a spatially separated aldehyde–alcohol cycle. In this self-protection system, an extracellular oxidase (WlsA) converts an alcohol precursor to a reactive aldehyde, while an intracellular reductase (WlsE) catalyzes the reverse reaction. The aldehyde product exhibits potent toxicity against termites in vitro, suggesting a potential role in ecological interactions. This work establishes a functional genomics platform that decodes cryptic ecological metabolism by integrating multiomics with heterologous pathway expression, providing a generalizable strategy for discovering and mechanistically understanding niche-specific natural products.