Tea Aphid-Induced β-Elemene Biosynthesis by CsELE Enhances JA-Dependent Herbivore Resistance in Tea Plants

Herbivore-induced plant volatiles play a crucial role in enhancing plant resistance and adaptability. However, the key volatiles triggering this response and their activation mechanisms remain largely unknown. Although tea aphids (Toxoptera aurantii) are common tea plantation pests, the underlying biochemical pathways by which aphid-induced volatiles in Camellia sinensis contribute to aphid resistance are not well understood. In this study, we measured jasmonic acid (JA) accumulation induced by aphid feeding using LC-MS and DESI-IMS analysis. We also identified a diverse array of aphid-induced volatiles through GC-MS. Notably, tea aphids stimulated β-Elemene accumulation, enhancing 'Shuchazao' resistance to tea aphids. We also evaluated the insecticidal activity of β-Elemene through contact toxicity and repellent bioassays. For the first time, we identified aphid-induced CsELE as a terpene synthase enzyme catalyzing the final step in β-Elemene biosynthesis from farnesyl pyrophosphate. Transient overexpression and gene silencing of CsELE affected β-Elemene accumulation, thereby influencing tea plant resistance to aphids. Furthermore, Dual-Luciferase and Y1H assays revealed that MYC2a, a core transcription factor in the JA signaling pathway, positively regulates CsELE expression. Overall, this study advances our understanding of the transcriptional regulation of tea volatiles in response to pest attacks, providing new insights into the ecological significance of terpene volatiles under biotic stress.