Terpene synthase genes conferring aphid resistance via enhanced <i>d</i> -limonene and myrcene biosynthesis in purslane ( <i>Portulaca oleracea</i> L.)

Purslane is a valuable medicinal and edible plant with broad environmental adaptability, resulting in extensive germplasm diversity worldwide. This genetic diversity manifests not only in morphological traits but also in varying levels of resistance to aphid infestation. In this study, we conducted a field survey of aphid populations on 99 purslane accessions and performed controlled inoculation experiments to identify two accessions with extreme differences in aphid resistance: accession no. 66 (HS, highly susceptible) and accession no. 119 (HR, highly resistant). Behavioral assays revealed that aphids preferred feeding on the HS accession and exhibited higher reproduction rates. Comparative transcriptome analysis between the two accessions revealed significant enrichment of genes involved in the monoterpenoid biosynthesis pathway. Non-targeted metabolomic profiling further demonstrated that the levels of two monoterpenoid compounds, d-limonene and myrcene, differed significantly between the HS and HR accessions. Integrated transcriptomic and metabolomic analyses identified two terpene synthase (TPS) genes, PolA01G018740 and PolB01G006810, whose expression levels were strongly correlated with the differential accumulation of d-limonene and myrcene. The differential expression of these TPS genes probably underlies variations in monoterpene content that contribute to aphid deterrence. Our findings provide molecular and biochemical insights into the mechanisms of aphid resistance in purslane and identify candidate genes for breeding insect-resistant cultivars.