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

## TL;DR

This study explores how Pyrus betulifolia responds to drought stress at the molecular level, identifying key genes and pathways involved in its drought tolerance.

## Contribution

The study provides a detailed temporal analysis of gene expression and identifies novel regulatory genes in Pyrus betulifolia under drought stress.

## Key findings

- Transcriptional changes peaked at 6 hours after PEG-induced stress, indicating a critical reprogramming phase.
- Genes related to osmotic adjustment and oxidative stress were significantly upregulated between 6 and 12 hours.
- WGCNA identified key regulatory genes like NF-Y, RVE1, and C2C2 zinc finger proteins as potential drought response regulators.

## Abstract

Drought is a major environmental constraint limiting crop growth and fruit yield. Due to its high drought tolerance, Pyrus betulifolia is widely used as a rootstock for pear cultivation; however, its molecular response mechanisms and transcriptional regulatory features under drought stress remain insufficiently characterized. In this study, we systematically analyzed the temporal transcriptomic responses of pear leaves under PEG-induced osmotic stress conditions. The results revealed a rapid transcriptional reprogramming stage, with the most pronounced gene expression changes occurring at 6 h after stress treatment. During this stage, multiple biological pathways associated with osmotic adjustment, oxidative stress responses, and cellular protection were significantly enriched, suggesting their potential involvement in drought adaptation. Furthermore, co-expression network analysis identified a set of putative key regulatory genes, providing valuable candidates for future functional validation. Collectively, this study delineates the temporal dynamics of osmotic-responsive transcriptional regulation in P. betulifolia and identifies key candidate genes, providing a molecular framework for further elucidation of stress tolerance mechanisms and supporting drought resistance breeding efforts.

Drought stress severely restricts the growth of pear trees. As a widely used drought-tolerant rootstock, Pyrus betulifolia 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 P. betulifolia 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 P. betulifolia and offer valuable candidate gene resources for further functional studies and drought tolerance breeding.