Deciphering the Temporal Transcriptional Dynamics and Key Regulatory Networks of Pyrus betulifolia in Response to PEG-Induced Osmotic Stress

Drought stress severely restricts the growth of pear trees. As a widely used drought-tolerant rootstock, <i>Pyrus betulifolia</i> exhibits stable growth performance; however, the molecular mechanisms underlying its drought tolerance remain to be elucidated. In this study, we investigated the molecular responses of <i>P. betulifolia</i> leaves to osmotic stress induced by 20% PEG-4000 using time-series RNA-seq technology. A total of 3745 differentially expressed genes were identified, with transcriptional changes peaking at 6 h, indicating a critical phase of transcriptional reprogramming during drought response. Genes associated with osmotic adjustment (e.g., P5CS) and oxidative stress responses (e.g., SOD and POD) were significantly upregulated between 6 and 12 h. Weighted gene co-expression network analysis (WGCNA) identified three distinct temporal modules and screened out NF-Y, RVE1, COL9, COL6, C2C2 zinc finger proteins, and Pseudo ARR-B as putative key regulators, whose expression patterns were validated using qRT-PCR. Collectively, these results provide a comprehensive view of the temporal transcriptional dynamics of drought response in <i>P. betulifolia</i> and offer valuable candidate gene resources for further functional studies and drought tolerance breeding.