关键词: 茄子, 果色, 上位基因, 花青素, 转录组, 代谢组

Abstract: 【Objective】Peel color is closely related to the appearance and value of eggplant. Anthocyanin is one of the natural pigments that determines an eggplant’s peel color. Through the comparison of gene expression and metabolites as well as the analysis on the mechanism of epistatic gene interaction and regulation of anthocyanin synthesis in eggplant peel, this paper provides a theoretical basis for eggplant breeding with different peel colors.【Method】White-peel female parent 19141 with mutation at the structural gene ANS of anthocyanin biosynthesis pathway, white-peel male parent 19147 with mutation at regulatory gene MYB1 of anthocyanin biosynthesis pathway, and their F₁ hybrid E3316 with reddish-purple-peel were used as test materials, while transcriptome sequencing and wide-targeted metabolome analysis were performed on peels of commercial eggplant.【Result】Transcriptome sequencing analysis showed that: 19141_ vs _ 19147 had the most differentially expressed genes (DEGs), followed by E3316_ vs _ 19141. The two comparison groups both had the significant enrichment of DEGs in the flavonoid pathway. The DEGs of E3316_ vs_ 19147 were the least and were not enriched in the flavonoid pathway. A total of 218 metabolites were detected by wide-targeted metabolome analysis. A total of 113 differential accumulated metabolites (DAMs) were detected in E3316_ vs _ 19141, and totally 98 DAMs were detected in E3316_ vs_ 19147. Combined analysis of transcriptome and metabolome found that the relative expression levels of key structural genes CHS, CHI, F3H, DFR and ANS, key regulatory genes MYB1, AN1 and AN11, modifier genes 3GT, 5GT, AT and OMT, and transporter gene AN9 (GST) involving anthocyanin biosynthesis pathway had the relation of 19141 > E3316 > 19147. The contents of anthocyanin metabolite cyanidin (CAS: 528-58-5) and cyanin (CAS: 20905-74-2) related to peel coloration had the relation of E3316 > 19147 > 19141. The combined analysis of transcriptome and metabolome both showed that the difference of E3316_ vs _ 19141 was bigger than E3316_ vs_ 19147. Under the regulation of epistatic genes, F3'H and F3'5'H genes were expressed simultaneously in eggplant peel, but the expression level of F3'H was much higher than that of F3'5'H. The anthocyanin content of E3316 was higher than that of its parents, and the chlorogenic acid content was lower than that of its parents. 【Conclusion】Under the interaction of epistatic genes that control the peel color, the locus (type) and mutation mode of mutant gene in parent determine the trend of gene expression in the whole anthocyanin metabolism pathway and the inhibition mode of peel pigmentation. If the mutated gene is a structural gene of the anthocyanin biosynthesis pathway, the gene expression of the whole pathway will not be affected, but the loss of function in key enzymes causes interruption of pathway, and results in the white peel of the parent. If the mutated gene is an MYB transcription factor gene, which almost downregulates the expression of all genes in the anthocyanin biosynthesis pathway, and anthocyanin transport may be blocked, resulting in white peel of the parent. The reddish-purple-peel F₁ hybrid of two white-peel parents is the result of the function complementation of two mutated gene involved in anthocyanin biosynthesis pathway. The highly expressed F3'H was the main cause for synthesis of cyanidin, and the relationship between anthocyanin and chlorogenic acid biosynthesis was competitive in peels.

Key words: eggplant, peel color, epistatic genes, anthocyanins, transcriptome, metabolome