A 49-bp deletion of results in a double flower phenotype in .

The double flower is an important trait with substantial ornamental value. While mutations in TOE-type or () genes play a crucial role in enhancing petal number in ornamental plants, the complete mechanism underlying the formation of double flowers remains to be fully elucidated. Through the application of bulked segregant analysis (BSA), we identified a novel gene, (), characterized by a 49-bp deletion in double-flowered . β-Glucuronidase (GUS) staining and luciferase reporter assays confirmed that the 49-bp deletion in reduced its binding with . Phylogenetic analysis and microsynteny analysis suggested that PmAP2L was not a TOE-type gene, and it might be a new gene controlling the formation of double flower in . Subsequently, overexpression of in tobacco led to a significant rise in the number of stamens and the conversion of stamens to petals. Furthermore, silencing of the homologue of in rose significantly reduced the number of petals. Using transient gene expression in flower buds, we determined the functional differences between and in controlling flower development. Meanwhile, DNA-affinity purification sequencing (DAP-seq), yeast hybrid assays and luciferase reporter assays indicated that PmAP2L negatively regulated the floral organ identity genes by forming a repressor complex with PmTPL and PmHDA6/19. Overall, these findings indicate that the variation in is associated with differences in the regulation of genes responsible for floral organ identity, providing new insights into the double-flower trait and double-flower breeding in plants.