Expression of anthocyanin biosynthesis-related genes reflects the peel color in purple tomato

Tomato (Solanum lycopersicum L.) is one of the most important and popular vegetables worldwide. A wide range of tomato cultivars with different colored fruits is presently available. The purple peel of tomato fruit is due to the accumulation anthocyanin pigments, which are beneficial to both plants and humans. Cultivated tomatoes normally do not make anthocyanin in their fruit peel, but there are some wild relatives of cultivated tomato like Solanum chilense, S. habrochaites, S. cheesmanii, and S. lycopersicoides that do produce anthocyanins in their fruits. In this study, the purple fruit color was obtained by crossing 'OSU blue' (blue fruit) and 'Purple mini' (brown fruit) and subsequent self-pollination. Anthocyanins are produced via the flavonoid pathway and are regulated by the transcriptional complex of MYB, bHLH, and WD40 repeats transcription factors. We determined the expression profiles of genes related to anthocyanin biosynthesis in tomato genotypes with distinct fruit colors by qRT-PCR. Both the early and late biosynthetic genes of the anthocyanin pathway were up-regulated in the peels of purple tomato fruits, except Sl5GT. Moreover, the expression of the regulatory genes SlANT1 and SlAN1 was dramatically increased in the peels of purple tomato fruits. These results indicate that SlANT1 and SlAN1 might play an important role on anthocyanin biosynthesis in the peels of purple-fruited tomatoes via up-regulation of structural genes in the anthocyanin pathway.