Qualitative and quantitative control of carotenoid accumulation in flower petals

• Carotenoid profiles of flower petals vary among plant species or cultivars.
• Mechanisms underlie the diverse carotenoid profiles of petals are summarized.
• Plants having unique carotenoids in their petals are introduced.

Carotenoids are lipophilic pigments widely distributed in nature. Among pigments produced in plants, carotenoids are unique in that they possess diverse functions depending on the organs and tissues in which they accumulate. The widely varying quantitative and qualitative composition of carotenoids among organs and tissues reflects these diverse functions. The green tissues of most plants show similar carotenoid profiles: Lutein, β-carotene, violaxanthin, neoxanthin, and zeaxanthin, essential components for photosynthesis, are invariably found. In contrast, carotenoid profiles of petals vary among plant species or cultivars and furnish distinct colors ranging from yellow and orange to red that attract pollinators. There is increasing evidence that the carotenoid content of petals is regulated not only by flux through the carotenoid biosynthesis pathway but also by degradation and by sequestration into chromoplasts, which function as sink organelles. These processes are mostly controlled at the transcriptional levels of relevant genes. In this review, the mechanisms that underlie the diverse carotenoid profiles of flowers are summarized with a major focus on molecular events that occur during carotenogenesis in petals.