Carotenoids are the most important biocolor isoprenoids responsible for yellow, orange and red colors found in nature. In plants, they are synthesized in plastids of photosynthetic and sink organs and are essential molecules for photosynthesis, photo-oxidative damage protection and phytohormone synthesis. Carotenoids also play important roles in human health and nutrition acting as vitamin A precursors and antioxidants. Biochemical and biophysical approaches in different plants models have provided significant advances in understanding the structural and functional roles of carotenoids in plants as well as the key points of regulation in their biosynthesis. To date, different plant models have been used to characterize the key genes and their regulation, which has increased the knowledge of the carotenoid metabolic pathway in plants. In this chapter a description of each step in the carotenoid synthesis pathway is presented and discussed.

Metabolic engineering is a main focus of many plant biotechnology programs that look for the production of novel plant varieties with improved human health benefits. Among the most interesting goals are those that are focused in the production of functional fruits. A fruit can be considered as functional if it produces additional benefits to human health and well-being, beyond nutrition. Fruits that present higher levels of beneficial compounds such as essential vitamins, antioxidants, and phytochemicals can be considered as functional as those compounds have long-term benefits in reducing the occurrence of certain diseases. Through the expression, silencing, or mutagenesis strategies, many functional fruit crops have been produced during the last 40 years. Novel plants produce higher amount of carotenoids, antocyanins, and folic acid in their fruits, as well as higher color, sweetness, flavor, and aroma. The improvement of postharvest and resistance to biotic and abiotic stress in commercial plants has been also enhanced as it can led to a better fruit production. Taken together, this chapter will present a revision of the main fruits that have been improved by means of metabolic engineering within the framework of functional foods and super foods.