Carotenoids and Their Derivatives: A “swiss Army Knife-Like” Multifunctional Tool for Fine-Tuning Plant-Environment Interactions

Plants have to cope with different biotic and abiotic stresses, such as the attacks of pathogens and herbivores, high irradiance, droughts, salt stress or nutrient deficiencies throughout their lifetime. These environmental perturbations lead to the regulation of the “primary” and “secondary” carotenoid network. The formers are produced and stored in plastids and they are necessary for photosynthesis and related functions. Otherwise, secondary carotenoids are derivatives of primary carotenoids. They perform other important functions not related to the photosynthetic process but essential for plant survival as regulators of growth and development or as signal molecules at all levels of plant organization. This review provides a complete revision of the status of all these carotenoids, highlighting their newly discovered functions involved in plant-environment interaction. Concurrently, this review covers recent information on how carotenoids perform critical functions for the survival of animals (including humans) and the way they are suitable diagnostic tools for assessing the functioning of terrestrial ecosystems.