Abstract: Bioinformatic characteristics and protein subcellular localization of AmaDOPA5-GT gene in Amaranth tricolor were studied.The chromosome walking technique was applied to clone the gene promoter.The protein was found to be located in the cytomembrane.Eight light-responsive elements were identified in the promoter,suggesting that light might be associated with the regulation of the gene expression.The amaranthin content and quantitative real time PCR showed that darkness suppressed both betalain biosynthesis and AmaDOPA5-GT gene expression;red light also suppressed betalain biosynthesis,but significantly enhanced the gene expression;yellow and green light showed no effect on the gene expression,but suppressed the betalain biosynthesis;and,blue light induced both betalain biosynthesis and the gene expression.The results obtained provided a basis for further exploring the function of AmaDOPA5-GT in betalain biosynthesis,as well as a guideline for breeding betalain-rich amarnath.