Travel advice on the road to carotenoids in plants

The carotenoids are a major class of organic pigments produced in plants and microbes. They fulfill many essential physiological and developmental processes in plants, and also have important roles in animal health and nutrition. As such they have been the focus of multidisciplinary research programs aiming to understand how they are synthesized in microbes and plants, and to clone genes encoding the corresponding enzymes and express them to modulate carotenoid production in recombinant microbial and plant systems. Our deeper understanding of carotenogenic gene regulation, in concert with the development of more effective multi-gene transfer systems for plants, has facilitated more ambitious strategies for the modulation of plant carotenoid biosynthesis not only in laboratory models but more importantly in staple food crops. Here we review the genetic and molecular tools and resources available for fundamental and applied carotenoid research, emphasizing recent achievements in carotenoid engineering and potential future objectives for carotenoid research in plants.