Integrated multi-omics analysis uncovers the mechanism of girdling-induced adventitious root formation in tree peony

Tree peony ( Paeonia sect. Moutan) is an important ornamental species with notable economic and ecological value. However, its large-scale cultivation is constrained by difficulties in propagation. Girdling has recently emerged as an effective method to promote adventitious root (AR) formation in tree peony, yet the underlying regulatory mechanisms remain insufficiently understood. In this study, we examined the effects of girdling time on rooting and elucidated the molecular basis of girdling-induced AR formation using multi-omics approach. We determined that 50 days after flowering (DAF) was the optimal stage for girdling. Transcriptome analysis identified 6 375 differentially expressed genes (DEGs), primarily enriched in plant hormone signal transduction and starch and sucrose metabolism pathways. A total of 1 511 metabolites were detected and classified into 13 categories. Weighted gene co-expression network analysis (WGCNA) revealed 48 hormone-related genes and 20 transcription factors associated with hormone signaling. Integrated transcriptomic and metabolomic analyses further indicated that seven transcription factors (including PrSCL8, PrSHR2, and PrERF109) play key in AR formation. Functional validation demonstrated that overexpression of PrSAUR32 and PrSCL8 in Arabidopsis significantly enhanced AR development, increasing both root number and length. Overall, our study elucidates the regulatory network underlying girdling-induced AR formation in tree peony and provides a theoretical foundation to support improved cultivation practices and industrial scale propagation through softwood girdling.