Integrated transcriptome, metabolome and activity-guided fractionation of Parnassia wightiana Wall. reveal its...

Parnassia wightiana Wall. (P. wightiana) is a traditional medicinal herb with demonstrated potential for developing eco-friendly botanical insecticides, but its insecticidal properties remain underexplored.

Here, we systematically evaluated the insecticidal activities of different plant tissues through integrated bioactivity assays and metabolomic profiling. Combining bioactivity-guided fractionation with transcriptomic analysis, we identified bioactive insecticidal compounds and elucidated key genes involved in secondary metabolite biosynthesis.

Bioassays revealed that root extracts exhibited the highest insecticidal efficacy against third-instar Mythimna separata (M. separata) larvae, with a median lethal concentration (LC₅₀) of 19.659 mg/mL. Integrated multi-omics analysis showed significant enrichment of terpenoid biosynthesis pathways in roots, including diterpenoid, sesquiterpenoid, triterpenoid, terpene backbone, and monoterpenoid metabolism. Notably, terpene synthase (TPS) substrates (Z, Z-FPP, Z,E-FPP, and E, E-FPP) were identified as critical precursors in terpenoid anabolism, with TPS-a subfamily genes potentially playing pivotal roles in synthesizing bioactive sesquiterpenes. Through bioactivity-guided isolation, we characterized Celahin B as a potent insecticidal sesquiterpenoid, showing remarkable toxicity against M. separata larvae (LC₅₀ = 116.642 µg/mL).

These findings advance our understanding of insecticidal metabolite biosynthesis in P. wightiana and provide a foundation for metabolic engineering of insecticidal compounds, and development of novel biopesticides with reduced environmental impact.