Study on the Positive Regulation of Drought Tolerance by PdMYB2R032 Based on R2R3-MYB Gene Family Analysis in Populus deltoides

Plants growing in natural environments are constantly exposed to various biotic and abiotic stresses, among which drought is a major abiotic factor that severely limits growth and development. As a water-demanding species, Populus is particularly vulnerable to drought under the context of global climate warming, making its drought tolerance a key determinant of adaptability and productivity. R2R3-MYB transcription factors play critical regulatory roles in plant responses to drought stress. In this study, we performed a comprehensive genome-wide identification and analysis of the R2R3-MYB gene family in P. deltoides ‘I-69’ using bioinformatics approaches, and further investigated the drought-responsive function of PdMYB2R032 through transgenic experiments. A total of 100 R2R3-MYB genes ( Pd2RMYBs ) were identified and classified into 12 subgroups based on phylogenetic analysis. Cis -element analysis of promoter regions revealed abundant motifs related to light response, hormone signaling, and drought regulation. Gene Ontology (GO) annotation indicated that Pd2RMYBs are potentially involved in hormone signaling pathways and responses to abiotic stresses. Phylogenetic analysis showed that PdMYB2R032 from P. deltoides × P. euramericana ‘Nanlin895’ is most closely related to Pd2RMYB21 in P. deltoides ‘I-69’. Functional studies revealed that overexpression of PdMYB2R032 in Arabidopsis thaliana significantly promoted root development and biomass accumulation under drought conditions. In addition, PdMYB2R032 regulated stomatal movement by reducing stomatal aperture under drought stress, thereby minimizing water loss. It also reduced malondialdehyde (MDA) accumulation, alleviating drought-induced oxidative damage. Furthermore, PdMYB2R032 enhanced seed germination, accelerated flowering, and shortened the reproductive cycle in transgenic Arabidopsis . Collectively, these results demonstrate that PdMYB2R032 acts as a positive regulator of drought tolerance through multiple biological pathways, providing theoretical support for elucidating the drought-responsive mechanisms of R2R3-MYB genes and for molecular breeding of drought-resistant poplars.