The MADS-box gene family, particularly the ABCE-class genes, plays a pivotal role in regulating floral development and reproductive processes in angiosperms. Expansion of the MADS-box gene family through ancient whole-genome duplications and lineage-specific duplication events has generated extensive regulatory flexibility across flowering plants. This review summarizes current findings on the evolutionary expansion and functional diversification of MADS-box genes, with a focus on the evolution of the ABCE-class in ornamental plants. We highlight how differential gene retention, expression divergence, and functional specialization have shaped the remarkable morphological diversity of floral organs across flowering plants. Comparative analyses across angiosperms reveal a lineage-dependent distinction between phylogenetic A-class genes and the developmental A-function: while AP1 represents the canonical A-class gene in core eudicots, AGL6-like genes fulfill ancestral A-function roles in early-diverging angiosperms, magnoliids, and monocots. Lineage-specific expansion and rewiring of ABCE gene networks, as observed in Orchidaceae, Asteraceae, and Rosaceae, have enabled reassembly of MADS-box protein complexes and rebalancing of expression domains, driving innovative floral forms. Beyond floral development, numerous MADS-box genes have diversified to function in flowering-time regulation and environmental stress responses, highlighting their broader adaptive significance beyond reproduction. This review provides an integrated evolutionary and functional perspective on MADS-box genes plasticity, and offers valuable insights for ornamental plant breeding and horticultural improvement.

Floral color and scent are crucial for plant–environment interactions, especially in reproduction by attracting pollinators for fertilization. They also have wide applications in cosmetic, pharmaceutical, and nutraceutical industries. Plant pigments are typically classified as chlorophylls, flavonoids, carotenoids, and betalains, while volatile organic compounds (VOCs) are grouped as terpenes, phenylpropanoids/benzenoids, and fatty acid derivatives. Significant progresses have been made in understanding the biosynthesis and regulation of these floral pigments and VOCs. Despite differences in their biosynthetic pathways, floral pigments and VOCs are biochemically connected and exhibit synergistic interactions during flower development and in response to biotic and abiotic stresses, suggesting the existence of pleiotropic regulators or complex mechanisms co-regulating their biosynthesis. In this review, we summarize and outline the metabolite pathways mainly integrating flavonoids, carotenoids, terpenes, and phenylpropanoids/benzenoids. We also provide a series of scenarios illustrating the coordinated regulation of floral color and scent. Finally, we suggest areas for future research. We hope this review will spark interest in this research direction and stimulate further studies.