Huperzia serrata Thallus as a Host-Derived Elicitor Enhances Alkaloid and Terpenoid Biosynthesis in a Sporothrix Endophyte: Insights from Multi-Omics

Endophytic fungi from Huperzia serrata (H. serrata) are promising sources for exploring novel acetylcholinesterase (AChE) inhibitors. In this study, 111 endophytic fungal strains were isolated from wild H. serrata, of which 18 exhibited AChE inhibition rates exceeding 90%. Among them, an endophytic Sporothrix isolate (HS2-S-26) showed a 98.37% AChE inhibition rate and could produce a range of AChE inhibitors, including dauricine. Comparative metabolomics and transcriptomics between H. serrata thallus (HT)-treated and untreated cultures revealed that the HT elicitor reprogrammed HS2-S-26 metabolism, affecting 6708 genes and 49 secondary metabolites. Alkaloids and terpenoids were the two largest classes, containing 10 and 11 compounds, respectively. Differential metabolites and differentially expressed genes were co-enriched in 59 KEGG pathways related to the biosynthesis and metabolism of alkaloids, terpenoids, and tyrosine metabolism, etc. HT likely promoted alkaloid accumulation by upregulating the expression of tyrosine biosynthesis genes (AROF, TYR1, GOT2, and ARO8) and may also enhance the supply of dopamine, potentially contributing to dauricine accumulation. Meanwhile, HT may promote terpenoid biosynthesis via activation of core pathway genes (MVAK2, GGPS1, FDFT1) and inhibition of branch pathway genes (COQ2, WRBA). Through multi-omics, this study demonstrates that host thallus acts as an effective elicitor of endophytic secondary metabolism, offering insights into host–endophyte regulatory crosstalk.