PtrWRKY75 overexpression reduces stomatal aperture and improves drought tolerance by salicylic acid-induced reactive oxygen species accumulation in poplar

•A drought tolerance gene PtrWRKY75 was isolated from Populus trichocarpa.•PtrWRKY75 was localized to the nucleus and bound to the PHENYLALANINE AMMONIA LYASE 1 (PAL1) promoter.•PtrWRKY75 induced SA biosynthesis to increase ROS accumulation, leading to smaller stomatal aperture under drought stress.•Overexpression PtrWRKY75 improves drought tolerance in poplar.