Regulation of carotenoid metabolism in tomato

Carotenoids serve diverse functions in vastly different organisms that both produce and consume them. Enhanced carotenoid accumulation is of great importance in the visual and functional properties of fruits and vegetables. Significant progress has been achieved in recent years in our understanding of carotenoid biosynthesis in tomato (Solanum lycopersicum) using biochemical and genetics approaches. The carotenoid metabolic network is temporally and spatially controlled, and plants have evolved strategic tactics to regulate carotenoid metabolism in response to various developmental and environmental factors. In this review, we summarize the current status of studies on transcription factors and phytohormones that regulate carotenoid biosynthesis, catabolism, and storage capacity in plastids, as well as the responses of carotenoid metabolism to environmental cues in tomato fruits. Transcription factors function either in cooperation with or independently of phytohormone signaling to regulate carotenoid metabolism, providing novel approaches for metabolic engineering of carotenoid composition and content in tomato.