Carotenoid biosynthesis in Prunus species: from pathway and accumulation structure to diverse pigmentation

Prunus species, also known as stone fruits, include several eye-catching fruits such as cherries, plums, apricots, peaches, nectarines, etc., which have significant economic value and are widely cultivated worldwide. Carotenoids are important secondary metabolites contributing to stone fruits' aesthetic appeal and nutritional value. Carotenoids contribute hues ranging from pastel yellow to rich orange in Prunus fruits. Carotenoids accumulate in Prunus tissues through the action of chromoplasts, particular structures that store and stabilize these pigments, giving rise to their vibrant colors. The diversity in carotenoid types and levels among Prunus species and cultivars leads to diverse tissue colors, reflecting their genetic diversity and evolutionary adaptations. The most important genes related to coloration are PSY, LCYB/E, and BCH1, which are responsible for carotenoid biosynthesis, whereas CCDs and NCEDs are involved in the degradation of carotenoids. PSY leads to increased carotenoid accumulation, providing yellow and orange pigmentation. LCYB involved in β-carotene accumulation results in an orange color. LCYE can lead to lutein biosynthesis and contribute to yellow coloration. BCH1 contributes to yellow pigmentation. CCD4 plays an essential role in the flesh color of the fruit, leading to white flesh in Prunus fruits, especially peaches. NCED is involved in abscisic acid formation by degrading carotenoids. Despite the importance of carotenoids, the connection between carotenoid profiles and the diversity of Prunus fruits has received little attention in the past. This review outlines the present knowledge regarding the molecular diversity mechanisms of the carotenoid biosynthesis pathway in Prunus fruits.