Combined transcriptomic and proteomic analysis constructs a new model for light-induced anthocyanin biosynthesis in eggplant (Solanum melongena L.)

Light is a key environmental factor affecting anthocyanin biosynthesis. Our previous study demonstrated that Lanshan Hexian is a light-sensitive eggplant cultivar, but its regulatory mechanism is unknown. Here, delphinidin-3-[4-(cis-p-coumaroyl)-rhamnosyl-glucopyranoside]-5-glucopyranoside and delphinidin-3-[4-(trans-p-coumaroyl)-rhamnosyl-glucopyranoside]-5-glucopyranoside were identified as the main anthocyanin components in by ultra-performance liquid chromatography-tandem mass spectrometry. Three time points of anthocyanin accumulation, including the start point (0day), fastest point (5days), and highest point (12day), were investigated by using ribonucleic acid sequencing and iTRAQ technology. The corresponding correlation coefficients of differentially expressed genes, and differentially expressed proteins were 0.6936, 0.2332, and 0.6672. Anthocyanin biosynthesis was a significantly enriched pathway, and CHI, F3H, 3GT, 5GT, and HY5 were regulated at both transcriptional and translational levels. Moreover, some transcription factors and photoreceptors may participate in light-induced anthocyanin biosynthesis like the known transcription factors MYB113 and TT8. The transient expression assay indicated that SmMYB35, SmMYB44, and a SmMYB86 isoform might involve in the light-induced anthocyanin biosynthesis pathway. Finally, a regulatory model for light-induced anthocyanin biosynthesis in eggplant was constructed. Our work provides a new direction for the study of the molecular mechanisms of light-induced anthocyanin biosynthesis in eggplant. Eggplant (Solanum melongena L.) with purple peel is rich in anthocyanins, but the concentration is affected seriously by light in actual production. In this study, delphinidin-3-[4-(cis-p-coumaroyl)-rhamnosyl-glucopyranoside]-5-glucopyranoside and delphinidin-3-[4-(trans-p-coumaroyl)-rhamnosyl-glucopyranoside]-5-glucopyranoside were identified as the main intermediate products in Lanshan Hexian, and the underlying molecular mechanism of light-induced anthocyanin biosynthesis in eggplant were analyzed using ribonucleic acid sequencing and iTRAQ technology. Strikingly, the transient expression assay indicated that SmMYB35, SmMYB44, and a SmMYB86 isoform might involve in light-induced anthocyanin biosynthesis by directly or indirectly regulating the structural genes expression. These comprehensive dataset will be conducive to reducing the poor colour production under weak light conditions in the future.