Understanding the carotenoid biosynthetic pathway: Observation of four color variants of developing watermelon fruit

Abstract

The carotenoid biosynthetic pathway regulatory mechanisms leading to lycopene accumulation are well defined in the model fruit, tomato (Lycopersicon esculentum L.). The regulatory mechanisms leading to accumulation of other carotenoids and flesh colors, however, are poorly understood. The variety of flesh colors available in watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) fruit makes it ideal for investigating the regulation of the full pathway. Carotenoid accumulation was measured in seven watermelon varieties, representing four flesh colors and two ploidy levels, throughout fruit maturation. We found that the putative regulatory mechanisms controlling lycopene accumulation in red-fleshed fruit follows the same regulatory patterns as the other flesh color mutants with differing predominant carotenoids. In general, products downstream of the predominant carotenoid for each color mutant accumulate until a breaker stage (approx. 20 days post pollination) at which time the major carotenoid and its ...