Overexpression of , a Positive Regulator of Stomatal Density, Promotes Vegetative Growth in Poplar.

Poplar is an important fast-growing tree, and its photosynthetic capacity directly affects its vegetative growth. Stomatal density is closely related to photosynthetic capacity and growth characteristics in plants. Here, we isolated from the hybrid poplar () clone 84K and investigated its biological function in vegetative growth. was expressed predominantly in young tissues and localized in the plasma membrane. Compared with wild-type 84K poplars, -overexpressing plants displayed an increased plant height, leaf area, internode number, basal diameter, biomass, IAA content, IPR content, and stomatal density. Higher stomatal density improved the net photosynthetic rate, stomatal conductance, intercellular CO concentration, and transpiration rate in transgenic poplar. The differential expression of genes related to stomatal development showed a diverged influence of at different stages of stomatal development. Finally, transcriptomic analysis showed that affected vegetative growth by affecting the expression of photosynthesis and plant hormone-related genes (such as , , , , , , and ). Taken together, our data indicate that could positively regulate stomatal density and increase the photosynthetic rate and plant hormone content, thereby promoting vegetative growth in poplar. Our study is of great significance for understanding the relationship between stoma, photosynthesis, and yield breeding in poplar.