Overexpression of PtrCWINV2 accelerates shoot growth and wood development in hybrid poplar (Populus davidiana × Populus bolleana).

Key message: PtrCWINV2 accelerates shoot growth and wood development in poplar via increased cellulose/lignin content, promoted sucrose allocation, enhanced hexose accumulation, and improved photosynthetic capacity. The transport of carbohydrates from source to sink organs is one of the major determinants affecting plant growth and development. Cell wall invertase (CWINV) of the invertase family catalyzes the decomposition of sucrose into hexoses, and regulates the loading and unloading of sugar in phloem. However, its functions in trees remain poorly understood. In this study, the poplar PtrCWINV2 gene was overexpressed in the hybrid clone Shanxin Yang (Populus davidiana × Populus bolleana), and its biological function was characterized. Overexpression of PtrCWINV2 promoted shoot growth and wood formation in transgenic poplar, as evidenced by the increased plant height, leaf number and size, stem diameter, and stem and leaf fresh weight. An increased xylem cell number and size, as well as phloem thickness, was also observed with microscopy. Further physiological analyses indicated that PtrCWINV2 overexpression modulated sucrose allocation and enhanced hexose accumulation along with photosynthetic carbon assimilation. Cellulose and lignin content, cellulose/lignin-related gene expression, soluble sugar accumulation, CWINV activity and photosynthetic rate were all improved in transgenic plants. Transcriptomic analysis revealed that the enriched pathways among the differentially expressed genes were well aligned with the physiological changes, corroborating the observed phenotypic correlation in transgenic plants. This study concludes that PtrCWINV2 represents a candidate gene for promoting tree growth and provides valuable insights for its application in the genetic improvement of wooden plants.