A model for enhancing drought resistance in poplar by miR159a overexpression. Overexpression of miR159a could reduce the open area of the stomata by increasing the expression level of the OST1 gene. Overexpression of miR159a also could enhance the drought resistance of poplar by altering the expression level of miR398 and downstream genes related to the drought pathway. Increased expression of miR159a increased the cleavage of downstream Pop_A03G020024 and Pop_A09G059498 transcripts under drought stress, which enhanced ROS scavenging systems. A, net photosynthetic rate; E, transpiration rate of leaf; Gsw, stomatal conductance; REC, relative electrical conductivity; WUE, water use efficiency.