Identification of the Regulatory Factor PsSPDS5 During the Senescence of Paeonia suffruticosa “Luoyang Hong” Cut Flowers

To investigate the molecular mechanisms underlying flower senescence in tree peony, we conducted transcriptome sequencing on potted Paeonia suffruticosa "Luoyang Hong" across 20 time points at 12-h intervals from initial bloom to full senescence. Comparative analysis of differentially expressed genes (DEGs) between the final (S19) and initial (S1) stages revealed significant enrichment in Gene Ontology (GO) terms spanning biological processes, cellular components, and molecular functions. A total of 10,351 DEGs were annotated to 816 GO pathways, with the "intrinsic component of membrane" category being the most enriched, containing 115 DEGs. KEGG pathway analysis further identified 968 DEGs enriched in 107 pathways, most notably in "plant hormone signal transduction." Based on expression pattern and functional annotation, PsSPDS5 was identified as a key candidate gene regulating senescence. We then cloned the PsSPDS5 gene from petal cDNA. Transient overexpression of PsSPDS5 significantly delayed senescence in cut flowers, demonstrating its positive regulatory role. In contrast, VIGS-mediated silencing of PsSPDS5 produced no discernible acceleration of senescence, most likely due to functional redundancy with other simultaneously upregulated spermidine synthase paralogs. This study identified a key gene associated with flower senescence in tree peony, which not only provides a new theoretical basis for regulating the postharvest quality of ornamental plants but also holds significant scientific value and application potential.