Genetically engineered anthocyanin pathway for high health-promoting pigment production in eggplant

Anthocyanins, natural pigments with high antioxidant activities, are widely distributed in the plant kingdom and play important roles in various physiological processes. Much effort has been committed to enhancing the anthocyanin content of these health-promoting pigments in vegetables and grains, for their eye-catching colors and special nutrients. Previously, we reported that the SmMYB1 gene encoding a R2R3 MYB transcription factor participated in the regulation of anthocyanin biosynthesis in the peel of eggplant. In this work, we introduced SmMYB1 into a non-anthocyanin-accumulating egg-plant cultivar (Solanum aethiopicum group Gilo) via Agrobacterium-mediated transformation. Genetically engineered plants exhibited high concentrations of anthocyanin in leaves, petals, stamens, and fruit peels under normal growth conditions, especially in fruit flesh. Furthermore, highly methylated anthocyanins, malvidin 3-(p-coumaroyl) rhamnoside(glucoside)-5-glucoside and malvidin 3-(feruloyl)rhamnoside(glucoside)-5-glucoside, were separated from the purple fruit flesh and identified by HPLC-ESI-MS/MS. qRT-PCR analysis revealed that most anthocyanin structural genes were dramatically up-regulated in the tissues of transgenic lines compared with non-transformed plants. In addition, the transgenic seedlings had greater tolerance to freezing stress and better recovery under rewarming conditions. These results provide a good foundation for the breeding of new eggplant cultivars with more healthy agronomic traits in future studies.