Transcriptomic and metabolomic analyses uncover the molecular defense strategy of Mikania micrantha under feeding stress from Pachypeltis micranthus

• Field evidence shows Pachypeltis micranthus herbivory suppresses Mikania micrantha growth. • Feeding triggers transient activation of defense enzymes and shifts in metabolite shifts. • 7889 herbivory-specific DEGs and 3577 DAMs were identified after filtering. • Herbivory induces transcriptional reprogramming from growth/defense to cell death. • ABC transporters, phenylpropanoid, and ALA metabolism are key defense key pathways. Pachypeltis micranthus , a herbivorous insect native to China, holds potential as a biological control agent for the invasive weed Mikania micrantha . However, the molecular responses of M. micrantha to insect feeding remain largely unexplored. Here, we showed that P. micranthus herbivory significantly suppressed M. micrantha growth and induced visible symptoms such as leaf yellowing and wilting in the field. Biochemical assessments revealed marked changes in the activity of defense-related enzymes and hormone concentrations under herbivore stress. We performed integrated transcriptomic and metabolomic analyses of tissues damaged by herbivores to investigate the underlying molecular mechanisms and identified 7889 herbivory-specific differentially expressed genes (PmDEGs) and 3577 herbivore-specific differentially accumulated metabolites (PmDAMs). Functional clustering and enrichment analyses revealed the activation of defense and damage-associated pathways within the first 48 h, followed by the downregulation of immune-related genes and upregulation of senescence and cell death pathways. Combined analysis of PmDEGs and PmDAMs indicated that ABC transporters, phenylpropanoid biosynthesis, and α-linolenic acid (ALA) metabolism were central response pathways. Furthermore, 24 lipoxygenase ( LOX ) genes involved in the ALA pathway were identified, and these were strongly expressed under herbivory, many of which contained cis-elements responsive to hormonal and stress-related signals. Our findings provide new insights into M. micrantha ’s defense strategies against herbivory, as well as key targets for the future development of biocontrol strategies.