Vital roles of carotenoids in plants and humans to deteriorate stress with its structure, biosynthesis, metabolic engineering and functional aspects

Abstract Carotenoids are long conjugated isoprenoid molecules with over 1117 identified structures, belongs to the class of hydrocarbons, involved in a range of biological processes in plants and humans. In plant cells, plastids are the organelles that play a central role in governing biosynthesis, stability and activity of carotenoids, and their diversity. In photosynthetic tissues, carotenoids act as accessory light‐harvesting pigments and extend the range of light absorption, and also play a very important role in photoprotection. In non-photosynthetic tissues carotenoids act as colorants and precursors for isoprenoid. While in human cells, carotenoids contribute to the maintenance of skin health by increasing basal dermal defense against UV. Each of these phytochemicals produces a kind of protection against diabetes, cancer, and inflammatory diseases. In this review, we precise current knowledge of the genes and enzymes involved in carotenoids metabolism, their regulatory mechanisms underlying carotenoid accumulation. This review also discuss the impact of various types of plastids on carotenoids biosynthesis, accumulation, their metabolic engineering and functions as stress signals in plants.