Increases Tolerance to Drought Stress by Enhancing Lateral Root Formation in .

Roots are the main organ for water uptake and the earliest part of a plant's response to drought, making them of great importance to our understanding of the root system's response to drought. However, little is known about the underlying molecular mechanisms that control root responses to drought stress. Here, we identified and functionally characterized the AP2/ERF family transcription factor (TF) and the upstream target gene zinc-finger protein TF PtrYY1, which respond to drought stress by promoting the growth and development of lateral roots in . A root-specific induction of under drought stress was explored. The overexpression of () promoted root growth and development, thereby increasing tolerance to drought stress. In addition, PtrYY1 is directly bound to the promoter of under drought stress, and the overexpression of () promoted lateral root growth and development and increased tolerance to drought stress. An RNA-seq analysis of with wild-type (WT) poplar identified and , which share the same pattern of expression changes as . A qRT-PCR and cis-element analysis further suggested that and may act as potential downstream targets of PtrABR1 genes in the root response pathway to drought stress. In conclusion, these results reveal a novel drought regulatory pathway in which regulates the network through the upstream target gene PtrYY1 and the potential downstream target genes and , thereby promoting root growth and development and improving tolerance to drought stress.