Dissection of the PsSUT1 promoter and ABA-responsive PsABF-mediated regulation in Paeonia suffruticosa

Background Tree peony ( Paeonia suffruticosa ), a high-value ornamental, is prone to dwarfism and bud abortion in container cultivation owing to limited sucrose supply. Previous studies have shown that the sucrose transporter PsSUT1 facilitates sucrose transport and thereby promotes vegetative growth and flowering. Results We functionally characterized the PsSUT1 promoter, identified upstream ABA-responsive transcription factors, and validated their functions. Using chromosome walking, we cloned the 1,606-bp PsSUT1 promoter containing ABRE motifs. In tree peony, PsSUT1 expression was highest in petioles and lowest in roots; ABA increased transcripts across tissues, with ~ 5-fold induction in petioles. The pSUT1 ::GUS reporter confirmed promoter activity in transient Nicotiana benthamiana assays and in Arabidopsis thaliana promoter::GUS lines, with expression in seedlings, roots, leaves, and siliques and clear ABA-inducibility. To identify upstream regulators, we cloned four ABF transcription factors involved in ABA signaling ( PsABF1/2/3/7 ), which were highly expressed in petioles and strongly positively correlated with PsSUT1 expression. Yeast one-hybrid assays verified binding to the PsSUT1 promoter, and transient tobacco dual-luciferase/LUC imaging demonstrated positive transcriptional regulation of PsSUT1 . PsABF7-OE lines were more vigorous than WT, with significantly greater height and rosette diameter. They had lower sucrose levels in rosette leaves but higher levels in stems and siliques, and showed enhanced growth under high-sucrose conditions, suggesting more efficient exogenous sucrose utilization. Conclusions Together, our data elucidate the promoter architecture and upstream regulation of PsSUT1 and provide a foundation for breeding and cultivation strategies to alleviate sucrose limitation in container-grown tree peony.