Carotenoids are important pigments that determine the color of floral organs and fruits in horticultural plants, directly influencing their ornamental and economic value. Unlike that in photosynthetic organs such as leaves, the accumulation of carotenoids during the development and coloration of plant flowers and fruits is often accompanied by significant changes in chlorophyll degradation and levels of secondary metabolites such as flavonoids, a process that is coordinately regulated by a multi-level regulatory network. In recent years, research on the molecular regulatory mechanisms of carotenoid-mediated flower and fruit coloration in horticultural plants has developed rapidly. This paper comprehensively summarizes research progress in this field, clarifying the core roles of key enzymes encoded by carotenoid biosynthetic genes such as PSY and the processes of chromoplast differentiation and pigment storage in the diversity of metabolic pathways. This metabolic process is coordinately regulated at the transcriptional, post-transcriptional, and epigenetic levels. At the transcriptional level, transcription factors such as MYB, bHLH, NAC, WRKY, and AP2/ERF form complex regulatory networks, precisely maintaining the dynamic balance between carotenoid biosynthesis and degradation by targeting key genes including PSY, LCYB, and CCD4. At the post-transcriptional level, multiple mechanisms, including the stabilization of PSY by ORANGE proteins, ubiquitination-mediated protein degradation, PPR protein regulation, and miRNA-mediated post-transcriptional silencing, coordinately achieve fine-tuning of metabolic flux. Epigenetically, DNA methylation and histone modifications dynamically regulate the chromatin state of key genes, thereby affecting the spatiotemporal patterns of pigment accumulation. Meanwhile, environmental factors such as light and temperature, as well as phytohormone signals like ethylene and abscisic acid, can be integrated into the above regulatory network to jointly determine flower and fruit color. This paper comprehensively reviews this multi-level coordinated and interactive regulatory system, deeply reveals the balance mechanism of carotenoid biosynthesis and degradation in flower and fruit coloration, and based on this, analyzes key issues and development pathways for color improvement and molecular breeding of horticultural products, providing theoretical support and technical guidance for the precise regulation of color traits and quality improvement of horticultural products.
