Plant hues: decoding the apocarotenoid color palette

Apocarotenoids are a structurally diverse group of specialized metabolites produced by oxidative cleavage of carotenoids, which perform important physiological, ecological, and interspecific communication roles in plants. Pigmented apocarotenoids form a distinctive yet insufficiently explored subgroup within this class. This review critically resumes current knowledge on apocarotenoid pigments, emphasizing their organ specific distribution, the biosynthetic pathways controlling their accumulation, and their adaptive significance. Particular attention is devoted to carotenoid cleavage dioxygenases (CCDs), the key enzymes driving their formation, including their substrate specificity and tissue dependent activity. Selected case studies focus on ethnobotanically relevant species, in which these pigments contribute to pollinator attraction, tolerance to abiotic and biotic stress, and possible allelopathic interactions. Traditional applications as natural colorants, food ingredients, and nutraceuticals are also considered. Interestingly, several neglected species produce rare apocarotenoids with potential industrial value but remain still poorly characterized. Because functional data are still fragmentary for many taxa, deeper characterization of these compounds represents a promising avenue for understanding the evolution of specialized metabolism and for advancing applications in food, cosmetics, and pharmaceuticals. Similarly, identification of regulatory networks and biosynthetic enzymes is essential to enable sustainable biotechnological production of high value apocarotenoids in heterologous systems through targeted metabolic engineering strategies.