Integrating Transcriptomics and Metabolomics in Poplar to Uncover Crucial Genes and Metabolites in Response to Anoplophora glabripennis Infestation

Anoplophora glabripennis (ALB) is one of the most devastating stem-boring beetles. However, knowledge pertaining to the molecular regulation and key responses of poplars under ALB infestation remains limited. In this investigation, the transcriptomes and metabolomes of two different poplars with different resistances under ALB infestation were jointly analyzed, combined with phytohormone analysis. Two thousand one hundred ninety-five genes, including defense genes such as MYB44, NAC1, and DELLA, were significantly altered in both poplar varieties after ALB infestation. Notably, the elevated levels of JA accumulation, the differential expression of poplar-specific phenolic glycosides, and the significant accumulation of catechins in Populus tomentosa might be the key factors leading to the differential resistance. In addition, the key metabolic enzymes involved in the synthesis of catechins (DFR, LAR, 4CL, CHS, and F3H) were significantly upregulated in P. tomentosa. Intriguingly, the upregulation of numerous resistance genes and the downregulation of a few photosynthesis-related genes in resistant poplars reflect a trade-off strategy between defense and growth. Several transcription factors, including WRKY, were identified in the significant induction of SA and JA signaling pathways in poplars in response to ALB infestation. Taken together, this investigation marked an important step toward elucidating the insect resistance mechanisms in poplar and should provide crucial insights into the development of new insect-resistant poplar varieties.