PoARF19 interacts with PoYUC10 and PoGA2ox2 to modulate auxin and gibberellin levels to promote lateral roots development in tree peony

SUMMARY Tree peony is a worldwide horticultural crop with both ornamental and industrial value. However, the poor rooting efficiency in micropropagation hinders commercial propagation and industry development. To investigate the regulatory mechanisms underlying root development in tree peony, we performed multi‐stage transcriptome sequencing (RNA‐seq) and measured auxin and gibberellin content in root organs. Lateral roots (LRs) exhibited significantly higher auxin levels than primary roots (PRs), whereas gibberellin content showed the opposite trend. Through weighted gene co‐expression network analysis (WGCNA), gene ontology (GO) enrichment, and expression pattern analysis, we identified AUXIN RESPONSE FACTOR 19 (PoARF19) as a key transcription factor. The expression pattern of PoARF19 correlated with auxin accumulation, being significantly higher in LRs than in PRs. Subcellular localization confirmed that PoARF19 localizes to the nucleus, and both heterologous and homologous transformation assays demonstrated its role in promoting LR development. Biochemical analysis revealed that PoARF19 interacts with flavin‐containing monooxygenase YUCCA10 ( PoYUC10 ) and gibberellin 2‐beta‐dioxygenase 2 ( PoGA2ox2 ) via auxin response elements (AuxREs). Expression patterns of PoYUC10 and PoGA2ox2 were consistent with auxin content but inversely correlated with gibberellin levels in PRs and LRs. Transgenic experiments confirmed that PoYUC10 and PoGA2ox2 regulate LR development by modulating auxin and gibberellin levels, respectively. This study elucidates a mechanism by which PoARF19 promotes LR development through the regulation of PoYUC10 and PoGA2ox2 , thereby coordinating auxin and gibberellin pathways. These findings offer insights into how hormones synergistically regulate root development, and provide a theoretical basis and genetic resources for improving rooting efficiency in tree peony.