The transcription factor PeERF73 activates PeARF29 expression to contribute to lignification-associated secondary cell wall thickening in Moso bamboo

Secondary cell wall (SCW) thickening and lignification are important contributors to the mechanical strength and quality of bamboo culms. The thick-walled (TW) Moso bamboo variant exhibits markedly thickened culm walls and reduced lumen area compared with wild-type plants, accompanied by enhanced lignin accumulation during internode development. However, the transcriptional mechanisms associated with lignification-related wall reinforcement in bamboo remain unclear. Here, we identify an AP2/ERF-family transcription factor, PeERF73, as a positive regulator of lignin deposition associated with SCW thickening in Moso bamboo. PeERF73 directly activates the expression of the auxin response factor gene PeARF29. PeARF29 in turn upregulates lignin biosynthetic genes, leading to enhanced lignin deposition. Functional assays in both Moso bamboo and transgenic Arabidopsis thaliana showed that overexpression of PeERF73 or PeARF29 increased lignin content and was associated with increased SCW thickness. These results reveal a PeERF73–PeARF29 regulatory module associated with lignification-related SCW thickening in bamboo and suggest candidate targets for modifying lignin-related culm wall traits.