Temporal dynamics of jasmonate signaling and flavonoid biosynthesis in Elaeagnus angustifolia during sustained adult Anoplophora glabripennis herbivory

The Asian longhorned beetle ( Anoplophora glabripennis , ALB) is a devastating invasive pest threatening global forest ecosystems. Russian olive ( Elaeagnus angustifolia ) serves as a dead-end trap tree in which sustained adult feeding induces defensive gummosis that kills eggs and neonates. However, the time-dependent molecular events underlying this defense remain unresolved. In this study, we aimed to characterize the temporal defense dynamics of E. angustifolia twigs during continuous ALB herbivory. We integrated time-series RNA-seq (0, 6, 12, 24, and 72 h) with phytohormone and flavonoid profiling. Transcriptomic remodeling was most pronounced at 24 h, marking a shift from early salicylic acid and jasmonic acid signaling to phenylpropanoid-flavonoid biosynthesis. Time-lagged correlation analysis suggested pathway-specific coordination between hormone accumulation and transcriptional responses. Biochemical validation confirmed increased total flavonoids and PAL activity at 24 h, with distinct accumulation patterns for specific flavonoid aglycones and glycosides. Weighted gene co-expression network analysis further identified hub transcription factors (MYB, bHLH, WRKY) co-expressed with flavonoid structural genes; their predicted target genes were enriched in defense-related pathways, and the PAL-4 promoter contained cognate cis-elements matching their binding motifs. Our findings indicate that E. angustifolia mounts a temporally coordinated defense against ALB feeding, in which early jasmonate–salicylate signaling precedes late-stage flavonoid accumulation. This study provides molecular insights into trap-tree defense mechanisms and advances understanding of time-dependent induced defenses in woody plants.