Integrated Metabolome and Transcriptome Analysis Reveals a Regulatory Network of Fruit Peel Pigmentation in Eggplant (Solanum melongena L.)

The color of fruit peel is an economically important character of eggplant, and black-purple eggplant has received much attention for being rich in anthocyanin. However, the reason why different fruit peel colors form in eggplant is not well understood. In the present study, an integrative analysis of the metabolome and transcriptome profiles was performed in five eggplant varieties with different fruit colors. A total of 260 flavonoids were identified, and most of them showed significantly higher abundance in black-purple varieties than in other varieties. The transcriptome analysis indicated the activation of early phenylpropanoid biosynthesis genes (SmPAL, SmC4H, and Sm4CL) was more responsible for anthocyanin accumulation, while SmF3′5′H was the key factor for the formation of a purple color. Furthermore, two transcription factors, SmGL2 and SmGATA26, were identified as new hub genes associated with anthocyanin accumulation. The silencing of SmGL2 and SmGATA26 reduced anthocyanin accumulation in eggplant fruit peels, suggesting the possible involvement of SmGL2 and SmGATA26 in regulating anthocyanin biosynthesis. In addition, the pathway of plant hormone signal transduction was significantly enriched, indicating that phytohormones may cooperatively interact to modulate flavonoid biosynthesis. This study provides comprehensive information of flavonoid metabolites and new insights into the regulatory network of fruit coloration, which might be useful for the molecular breeding of eggplant.