Abstract
BACKGROUND: Soil heavy metal pollution by chromium (Cr) and copper (Cu) is a global environmental concern. METHODS: This study evaluated Cr/Cu accumulation in Paulownia fortunei tissues and analyzed its root transcriptome under Cr and Cu stress to elucidate molecular response mechanisms. RESULTS: Findings revealed significantly higher Cr and Cu accumulation capacity in roots compared to stems and leaves. Transcriptome sequencing identified 6017 and 2265 differentially expressed genes (DEGs) under Cr and Cu stress, respectively. These DEGs were primarily involved in redox reactions, stress responses, transcriptional regulation, transmembrane transport, and metabolism. Quantitative PCR of 20 selected genes validated dynamic expression changes under stress. Weighted Gene Co-expression Network Analysis (WGCNA) identified distinct co-expression modules associated with Cr and Cu. Hub gene analysis implicated Pfo_020668 and Pfo_019190 in Cr response, while Pfo_010312 and Pfo_000197 may enhance Cu tolerance via cell wall polysaccharide synthesis regulation. Pathways related to pyruvate metabolism and proteasome were significantly enriched under Cr stress, whereas amino acid metabolism pathways were prominent under Cu stress. CONCLUSIONS: Differentially expressed transporter genes suggest potential roles in heavy metal uptake and transport. This transcriptomic analysis provides novel insights into P. fortunei's molecular responses to Cr and Cu stress, offering a foundation for utilizing this species in soil phytoremediation efforts.