Heterologous expression of Pinus massonianaVNS2 enhances secondary cell wall deposition in poplar

NAC-domain transcription factors (TFs) play central roles in regulating secondary cell wall (SCW) biosynthesis during wood formation. In this study, we identified PmVNS2 , a VND-subfamily NAC gene from Pinus massoniana , encoding a 353-amino acid protein with conserved NAC domains. PmVNS2 was preferentially expressed in developing xylem. Heterologous expression in Populus davidiana × P . bolleana significantly enhanced plant growth, increased the number of secondary xylem cell layers, and thickened SCWs (3.45 ± 0.27 μm vs. CK: 1.91 ± 0.18 μm). Transgenic lines showed upregulated expression of lignin biosynthetic genes ( CCR2 , C4H2 ), cellulose synthase genes ( CesA2B , CesA3A ), and MYB transcription factors ( MYB021 , MYB128 ), while xylan biosynthesis genes ( GT43B , GT43D ) were downregulated. These results demonstrate that PmVNS2 is a key regulator of SCW formation in conifers, offering a promising genetic target for wood quality improvement.