Dietary anthocyanins are important health-promoting antioxidants that make a major contribution to the quality of fruits.It is intriguing that most tomato cultivars do not produce anthocyanins in fruit.However,the purple tomato variety Indigo Rose,which has the dominant Aft locus combined with the recessive atv locus from wild tomato species,exhibits light-dependent anthocyanin accumulation in the fruit skin.Here,we report that Aft encodes a functional anthocyanin activator named SIAN2-like,while atv encodes a nonfunctional version of the anthocyanin repressor SIMYBATV.The expression of SIAN2-like is responsive to light,and the functional SIAN2-like can activate the expression of both anthocyanin biosynthetic gen.es and their regulatory genes,suggesting that SIAN2-like acts as a master regulator in the activation of anthocyanin biosynthesis.We further showed that cultivated tomatoes contain nonfunctional alleles of SIAN2-like and therefore fail to produce anthocyanins.Consistently,expression of a functional SIAN2-like gene driven by the fruit-specific promoter in a tomato cultivar led to the activation of the entire anthocyanin biosynthesis pathway and high-level accumulation of anthocyanins in both the peel and flesh.Taken together,our study exemplifies that efficient engineering of complex metabolic pathways could be achieved through tissue-specific expression of master transcriptional regulators.