An R2R3-MYB transcription factor PdbMYB6 enhances drought tolerance by mediating reactive oxygen species scavenging, osmotic balance, and stomatal opening.

Drought is a major environmental challenge that hinders the growth and development of plants. R2R3-MYB transcription factors (TFs) play a vital role in mediating responses to abiotic stress; however, their specific functions in Populus davidiana × Populus bolleana hybrid poplar plants remain underexplored. This study focused on PdbMYB6, a novel R2R3-MYB TF identified in P. davidiana × P. bolleana plants. We found that PdbMYB6 acts as a transcriptional activator. By conducting functional analyses of both overexpression and knockout models, we demonstrated that PdbMYB6 enhances drought tolerance in plants by improving reactive oxygen species scavenging and modulating osmotic balance. Additionally, PdbMYB6 plays a role in regulating stomatal openings to minimize water loss. The qRT-PCR and RNA sequencing results revealed that PdbMYB6 influences the expression of genes related to stress tolerance. TF-centered Yeast One-Hybrid (Y1H) and chromatin immunoprecipitation (ChIP) assays indicated that PdbMYB6 binds to two novel core sequences (C [A/G/C]TG and [T/A/G]GTA) as well as GT-1 (GGAAA) and MYBCORE (AACGG) elements, which are associated with light responses and stress resistance, thereby promoting the expression of stress-resistant genes. Furthermore, Y1H and ChIP assays identified four upstream factors that regulate PdbMYB6 expression by interacting with specific elements in its promoter. Notably, the overexpression of these four factors enhances plant drought resistance and affects the expression of stress-response genes. Our findings highlight the role of the PdbMYB6 TF in the drought regulatory mechanism and provide potential gene sources for the molecular breeding of drought-resistant plants through genetic engineering.