Identification of the PoARFs gene family in tree peony and expression analysis of PoARF7 and PoARF10 in petals and stamens formation

Tree peony (Paeonia section Moutan DC.) produce strikingly large, vibrant blooms that exhibit remarkable morphological diversity, ranging from single petals to complex double forms, making them highly prized for ornamental horticulture. While auxin response factors (ARFs) are well-established as crucial regulators of organogenesis in model plants, the functional characterization of PoARF genes in tree peony remains largely unexplored. Genome-wide analysis identified 17 PoARF genes (PoARF1-PoARF17) in tree peony (Paeonia ostii). Their encoded proteins vary in length (420-993 aa) and molecular weight (47.2-109.8 kDa), with isoelectric points of 5.19-9.48 (mostly weakly acidic) and all predicted to localize to the nucleus. Phylogenetic analysis clustered the PoARFs into three clades (Groups I-III). All members contained eight conserved motifs (Motif1-7,9), indicating structural and functional conservation within this gene family. Gene architecture analysis revealed that most PoARF genes feature untranslated regions (UTRs) flanking both termini, while subgroup members exhibited remarkably similar exon-intron organizational patterns. Conserved sequence analysis result showed that the motif arrangement is relatively conserved within each subfamily. The promoter region of PoARF genes in tree peony contains four types of cis-regulatory elements, suggesting that it may be involved in biological processes such as light response, hormone regulation, and tissue-specific expression. The results of the instantaneous transformation test of tree peony showed that PoARF7 promotes petal development while inhibiting stamens development, whereas PoARF10 exhibits opposing functions. These results elucidate ARF-mediated control of floral organ ratios and provide a foundation for studying ARF genes family functions in woody angiosperms.