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

Abstract

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.

Genome-Wide Identification of Glutathione S-Transferase Genes in Eggplant (Solanum melongena L.) Reveals Their Potential Role in Anthocyanin Accumulation on the Fruit Peel

“…The majority of the structural genes involved in flavonoid biosynthesisincluding PAL, C4H, 4CL, CHS, CHI, F3H, DFR, ANS and UFGT had significantly lower levels of transcription in A2 (black-purple with green calyx cultivar) and A4, (reddish-purple eggplant cultivar), thus contributing to lower flavonoids in A2 and A4. Generally, most of the structural genes involved in flavonoid biosynthesis were highly expressed in A1 and A3 with black-purple fruit peels [44]. This provides valuable data for further research on the molecular mechanism underlying anthocyanin accumulation in eggplant fruit peel.…”

“…Some of the SmGST genes also showed a positive correlation with anthocyanin structural genes, indicating synergistic functions; while others have a negative correlation depicting antagonistic or different roles. In our previous research group, transcriptomic analysis [44] explored the expression of anthocyanin structural biosynthetic genes in the five different eggplant varieties. The majority of the structural genes involved in flavonoid biosynthesisincluding PAL, C4H, 4CL, CHS, CHI, F3H, DFR, ANS and UFGT had significantly lower levels of transcription in A2 (black-purple with green calyx cultivar) and A4, (reddish-purple eggplant cultivar), thus contributing to lower flavonoids in A2 and A4.…”

“…Fruit peel samples were collected 25 days post anthesis. The growth conditions and sampling of fruit tissues are well illustrated in the previous report [44].…”

“…The expression of SmGST genes was determined using RNA-seq data from our recent research group data [44] (Table S8). Eggplant cultivars of different peel colors were used, including: cultivars with dark-purple peel-A1; green peel-A2; black-purple with green calyx-A3; white peel cultivar-A4; and cultivars of reddish-purple-A5.…”

“…The expression data of eggplant SmGST genes among eggplant varieties of different peel colors were obtained from our recent research group RNA-seq data (PRINA868105) [44]. Briefly, the total RNA was extracted from fruit peels of the five varieties using the RNeasy Plant Mini Kit (Qiagen, Hilden, Germany).…”