Mechanism underlying the carotenoid accumulation in shaded tea leaves

•Long-term shading treatment (14 days) increased carotenoid content in tea leaves.•Long-term darkness (14 days) decreased carotenoid content in tea leaves.•Long-term shading treatment increased carotenoid biosynthetic gene expression levels.•Long-term darkness decreased carotenoid biosynthetic gene expression levels.•The functions of CsDXS1, CsDXS3, CsPSY, CsLCYB and CsLCYE genes have been verified.