Molecular mechanism of SmERF B3-4 in regulating lignin biosynthesis by modulating Sm4CL11 in Salix matsudana

Lignin deposition in plant cell walls influences plant growth and its production efficiency in industry. The lignification process involves complex biosynthetic pathways requiring coordinated gene interactions and is regulated by transcriptional networks mediated through transcription factor-DNA interactions. In Salix matsudana, exogenous ethephon application induced a dwarfing phenotype with reduced lignin accumulation in stems. Transcriptomic analysis of ethephon-treated samples identified Sm4CL11, a key gene involved in lignin biosynthesis. Virus-induced gene silencing (VIGS) of Sm4CL11 reproduced the dwarfing phenotype and decreased lignin deposition. Histochemical staining and Raman microspectroscopy revealed that Sm4CL11 regulates lignin content and spatial deposition patterns in vessel cell walls, confirming its essential role in the lignin biosynthetic pathway. WGCNA and promoter cis-element analysis identified SmERF B3-4, an upstream transcriptional regulator of Sm4CL11. Yeast one-hybrid assays and dual luciferase reporter assay (LUC) assays demonstrated direct binding of SmERF B3-4 to the Sm4CL11 promoter, activating its expression. This study elucidates molecular mechanisms underlying lignin biosynthesis regulation and provides valuable insights for which would contribute to the lignin-related chemical industry.