Molecular basis of carotenoid accumulation in horticultural crops

Carotenoids are isoprenoid pigments, which are widely distributed in nature. In fruits and flowers, carotenoids are responsible for bright yellow, orange, and red colors and provide a substrate to form flavor compounds, which attract pollinators and seed dispersers. In leaves, carotenoids play an essential role in photosynthesis. When carotenoids are ingested in the diet, they play a vital role in human nutrition and health as a precursor of vitamin A, antioxidants, and anti-inflammatory agents. It is therefore important to control carotenoid accumulation to improve the commercial value of horticultural crops. Carotenoid accumulation is regulated by flux through the carotenoid biosynthetic pathway, and also by degradation and sequestration into plastids, which function as sink organelles. These processes are mostly controlled at the transcriptional levels of relevant genes. In this review, we summarize recent advances in studies on the molecular mechanisms that regulate carotenoid accumulation in vegetables, fruits, and ornamental flowers.