PscCYP716A1-mediated brassinolide biosynthesis increases lead tolerance and enrichment in poplar

Urban soil lead (Pb) pollution poses a pressing threat to ecosystems and public health. Phytoremediation has emerged as an effective solution to address this issue. Poplars are widely employed in urban greening owing to their fast growth and high biomass, rendering them prime candidates for Pb remediation. However, their innate remediation capacity remains constrained, therefore, it needs to further enhance by genetic improvement. Transcriptome sequencing (RNA-seq) has identified that PscCYP716A1, a gene involved in brassinosteroid (BR) synthesis, is upregulated under Pb stress, indicating a potential role in Pb tolerance. This prompted a research question: Can PscCYP716A1 improve poplar's Pb tolerance? In this study, we obtained PscCYP716A1-overexpression poplars (OE lines, OE-13 and OE-42) and RNA interference PscCYP716A1-expression poplars (RNAi lines, RI-33 and RI-23). The overexpression poplars significantly enhanced Pb tolerance, and increased Pb accumulation compared to wild-type (WT). Further analysis revealed that PscCYP716A1 enhances Pb tolerance by improving the antioxidant system and Pb chelation. However, when exogenous brassinazole (BR biosynthesis inhibitor, BRZ) was sprayed on poplar under Pb stress, all advantages of OE lines disappeared. According to the results of analysis, the improvement of antioxidant and chelation capacities conferred by PscCYP716A1 may be related to its participation in the BR synthesis pathway. In summary, our results revealed the physiological mechanism and detoxification processes facilitated by PscCYP716A1, and underscored its potential as a genetic tool for enhancing phytoremediation in Pb-contaminated urban environments. These findings provide a theoretical foundation and technical support for the application of engineered poplars in remediating soil Pb pollution.