Phosphorylation of the transcription factor PoWRKY31 by PoKIN10 activates lignin biosynthesis to improve tree peony drought tolerance

The SNF1-Related Protein Kinase 1 (SnRK1) signaling cascade is highly conserved and plays a crucial role in coordinating various cellular processes in plants. However, its regulatory mechanisms in stress responses remain largely unclear. Here, we started from the perspectives of transcriptional regulation, protein-protein interaction, and posttranslational modification, and through the integration of multiple molecular biology approaches and functional validation methods, we conducted a detailed analysis of the mechanisms by which PoKIN10 (SnRK1 catalytic subunit), PoWRKY31, PoWRKY75, and PoCCoAOMT participate in drought tolerance in tree peony. We report a novel regulatory module that modulates lignin biosynthesis to enhance drought tolerance in tree peony. PoKIN10 acts as a key regulator of lignin-mediated drought tolerance by phosphorylating PoWRKY31 at the Ser262 residue, thereby enhancing its protein stability, DNA-binding affinity, and transcriptional activation activity. PoWRKY31 directly binds to the promoter of PoWRKY75 and activates its expression, which subsequently induces PoCCoAOMT expression, leading to increased lignin accumulation, improved water retention, and enhanced reactive oxygen species (ROS) scavenging capacity under drought stress. We therefore elucidate a regulatory module that governs lignin biosynthesis to improve drought tolerance in tree peony, offering new insights into lignin-mediated drought adaptation in plants.