Integrated Transcriptomic and Metabolomic Mining of Candidate Genes for Weevil Resistance in Pea

The pea weevil (Bruchus pisorum L.) causes severe yield losses in cultivated pea (Pisum sativum L.), yet the molecular basis of host resistance remains unclear. Here, we performed integrated transcriptomic and metabolomic analyses on pods and seeds of resistant (YWD) and susceptible (LW1) pea genotypes to characterize the constitutive defence network against weevils. Extensive transcriptional and metabolic reprogramming was observed in resistant materials, with upregulation of defence pathways and suppression of primary metabolism. Pods directed phenylpropanoid flux toward isoflavonoid biosynthesis and enhanced cutin/wax pathways, while seeds redirected flux to flavone/flavonol biosynthesis, accumulating high levels of flavone C-glycosides including isovitexin (5260.46-fold) and vitexin (3771.09-fold). We identified Dof21 as a key transcription factor putatively regulating flavonoid biosynthesis, with its Dof domain predicted to bind promoters of 4CL1, CHS3 and CYP75B. A seed-specific lectin gene LG16 showed 8.99-fold higher expression in resistant seeds with negligible expression in pods. The ABA catabolite dihydrophaseic acid and semi-volatile compounds vanilloloside and cimidahurinine were significantly enriched in resistant seeds, implicating ABA turnover and glycosylation in defence compound stabilization. This study provides a multi-dimensional molecular framework for weevil resistance in pea and offers key candidate genes including Dof21, LG16, 4CL1, CHS3 and CYP75B for resistant germplasm screening and marker-assisted breeding.