The activation of the NAC transcription factor by Poplar PtrGATA9 facilitates the secondary cell wall deposition of interfascicular fiber cell in Arabidopsis

The secondary cell wall (SCW) in plant is vital for the plant growth, as it contributes to their physical resilience, aids in the movement of water and nutrients, and supports overall plant development. A transcriptional regulatory layer carefully governs the precise spatial and temporal deposition of SCW components within specific plant cells. Even though the regulatory mechanism of SCW biosynthesis in Arabidopsis is well comprehended, studies on woody perennials remain limited. In this study, we characterized Poplar PtrGATA9 (Potri.001G188500), the poplar homolog of Arabidopsis AtGATA9 (AT4G32890), in regulating SCW biosynthesis. Over-expression of PtrGATA9 resulted in SCW thickening in interfascicular fiber cells, which was due to upregulated transcriptional expression of NAC-domain transcription factors and SCW biosynthetic genes downstream of NAC-domain transcription factors. Furthermore, the transfection assay of Arabidopsis protoplasts revealed that PtrGATA9 acts as a transcriptional activator for NAC-domain transcription factors, which are recognized as key master regulators of SCW biosynthesis. This suggests that PtrGATA9 functions as an upstream transcription factor for the NAC-domain transcription factors. Our findings offer valuable insights into the control of SCW biosynthesis in woody perennial plants and the potential significance of PtrGATA9 in enhancing plant growth and development.