Objective This study explored the effects of xyloglucan endoglycosidase/hydrolase gene PtoXTH34 in response to drought stress in poplar.

Method The PtoXTH34 of poplar was heterologously expressed in tobacco to investigate the changes in phenotype and parameters related to photosynthesis and stress resistance of transgenic tobacco under drought stress.

Result (1) Overexpression of PtoXTH34 gene can significantly reduce the rate of water loss in isolated tobacco leaves. (2) After 14 d of drought treatment, the control tobacco showed obvious wilting, while the leaves of overexpressing PtoXTH34 plants grew well and remained green. The height and stem diameter of plants overexpressing PtoXTH34 were significantly higher than those of control. (3) After 14 d of drought treatment, the net photosynthetic rate, stomatal conductivity, and transpiration rate of control were close to 0, while the photosynthetic indexes of overexpressing PtoXTH34 tobacco were significantly higher than those of control, and higher than before drought treatment. (4) After 14 d of drought treatment, both H₂O₂ and MDA contents in control increased significantly and were significantly higher than those in overexpressing PtoXTH34 plants, and the control plants showed accumulation of reactive oxygen species and significant leaf damage, while the overexpressed PtoXTH34 plants did not exhibit this phenomenon.

Conclusion Overexpression of PtoXTH34 in tobacco enhances drought resistance of plants by reducing water-loss rate of leaves, improving photosynthesis, and clearing accumulation of reactive oxygen species. This study lays the foundation for gene function of PtoXTH34 and enriches genetic resources for molecular breeding of trees.