The Function of RcAG2 and RcFUL in the Flower Shape Change of Rosa chinensis ‘Viridiflora’

The floral morphology of <i>Rosa chinensis</i> significantly influences its ornamental value. However, the molecular mechanisms underlying specific floral types remain poorly understood. Viridiflora, a stable genetic variant of <i>R. chinensis</i>, exhibits homeotic transformation of floral organs into sepal-like structures, providing a valuable model for studying floral organ identity and development. In this study, Viridiflora was compared with Old Blush to elucidate floral development through morphological observation, transcriptomic profiling, and functional genetics. Four distinct developmental stages were defined, encompassing the formation of sepal, petal, stamen, and pistil primordia. Transcriptome analysis identified candidate genes associated with the Viridiflora phenotype, among which <i>RcAGAMOUS2</i> (<i>RcAG2</i>) and <i>RcFRUITFULL</i> (<i>RcFUL</i>) were selected for in-depth functional characterization. The proteins encoded by these two genes are hydrophilic, lack signal peptides and transmembrane domains, and contain multiple phosphorylation sites. They feature typical MADS-box family domains and show close phylogenetic affinity to <i>Rosa rugosa</i>. Subcellular localization showed their nuclear presence. Heterologous overexpression of <i>RcAG2</i> and <i>RcFUL</i> in Arabidopsis resulted in notable phenotypic alterations: <i>RcAG2</i> caused petal reduction and stamen exposure, while <i>RcFUL</i> led to greenish, leaf-like petals with pigmentation gradients, increased sepal number, and failed seed set. Conclusion: These results suggest that <i>RcAG2</i> and <i>RcFUL</i> play key roles in floral organ development through genetic regulation, providing a theoretical foundation for further research on floral development in <i>R. chinensis.</i>