TY - EJOU AU - Li, Renjie AU - Li, Ruiya AU - Li, Yuying AU - Guo, Lili AU - Guo, Qi AU - He, Xiangnan AU - Zhou, Yunxin AU - Hou, Xiaogai TI - PsSEP3L1 Positively Regulates Petal Number in Tree Peony (Paeonia suffruticosa) by Interacting with MADS-Box Family Proteins T2 - Phyton-International Journal of Experimental Botany PY - VL - IS - SN - 1851-5657 AB - SEP3, one of the SEPALLATA (SEP) genes, plays a crucial role in the regulation of floral organ morphogenesis in plants. However, its specific function and molecular regulatory mechanisms remain largely unclear in tree peony (Paeonia suffruticosa Andr.). In this study, the PsSEP3L1 sequence of the tree peony cultivar ‘Luoyang Hong’ was obtained by homologous cloning. The open reading frame of PsSEP3L1 is 738 bp and encodes 245 amino acids. Phylogenetic analysis indicated that PsSEP3L1 was most closely related to the SEP3 homolog from cassava. The expression level of PsSEP3L1 in petals, petaloid petals, and stamens was significantly higher than that in sepals. Specifically, in the petaloid petals of the tree peony cultivar ‘Luoyang Hong’, the expression level was 23.73-fold higher than that in sepals. Functional assays demonstrated that overexpression of PsSEP3L1 significantly increased petal number in tree peony, whereas silencing of this gene resulted in a significant reduction in petal number, confirming its positive regulatory role in petal number determination. The Yeast two-hybrid and Bimolecular fluorescence complementation assays revealed that PsSEP3L1 protein interacts with MADS-box family proteins, including PsSEP1L, PsAP3, and PsAG. Collectively, PsSEP3L1 may participate in regulating petal number in tree peony by forming protein complexes with other MADS-box proteins, thereby contributing to floral organ morphogenesis. This study provides a basis for further mechanistic studies on floral organ morphogenesis in tree peony. KW - Tree peony; PsSEP3L1; MADS-box; floral organ DO - 10.32604/phyton.2026.083737