Proteomic and metabolomic analyses showing the differentially accumulation of NnUFGT2 is involved in the petal red-white bicolor pigmentation in lotus (Nelumbo nucifera)

Bicolor flower lotus is rare with high ornamental value. During the long history of breeding and artificial selection, a very famous lotus cultivar 'Da Sajin' with red and white picotee bicolor petals were obtained. In order to reveal the mechanism underlying the formation of its picotee bicolor pattern in the petal, an integrative metabolomics and proteomics analyses were conducted between red and white parts of its petals. The results showed that the defect of anthocyanidin 3-O-glucosyltransferases (UFGTs) accumulation resulted in the failure of the glycosylation of anthocyanidin, the last step of anthocyanin biosynthesis in white part of the petals. And proteomic data and biochemical analysis showed that the defect of UFGTs accumulation is not related to their transcription, but because of their degradation. Function of one differentially accumulated NnUFGT were proven being involved in anthocyanin biosynthesis through both in-vitro enzyme assay and in-vivo transgenic analyses. This regulation on the protein accumulation of structural genes in anthocyanin biosynthesis was not explored in any other plants, and hence supposed to be a novel mechanism for the formation of picotee bicolor pattern flower. The results not only provide some new insights into the understanding of lotus flower coloration, but also might assist the breeding of flower lotus.