Red and blue light promote tomato fruit coloration through modulation of hormone homeostasis and pigment accumulation

Understanding how light regulates pigment composition and accumulation is crucial for postharvest management of fruit quality and nutritional value. In this study, we investigated the influence of light quality, specifically the blue and red lights, on coloration of tomato fruit. We show that both lights expedite the progress of skin coloration in tomato fruit by promoting chlorophyll degradation, stimulating carotenoid biosynthesis, accelerating plastid conversion, and enhancing plant hormone (i.e., abscisic acid and ethylene) biosynthesis. However, red light shows higher efficiency in inducing color transition compared with blue light. Gene expression network analysis unraveled several modules that are associated with carotenoid metabolism and hormone biosynthesis in response to light treatments, among which the transcription factors including WRKY20, MYB12, ARR11, NAC16, bHLH46, ZNF69, and MYB58 were identified as potential key regulators. Collectively, our data provide new threads on the regulation of fruit coloration by light quality and highlight the potential utility of red LED treatment to improve the color and quality of tomato fruit.