Metabolic profiling and transcriptome analysis provide insights into the accumulation of flavonoids in chayote fruit during storage

Chayote (Sechium edule) fruits are rich in flavonoids, folate, and low-calorie food. However, studies about the flavonoids and regulatory mechanism of flavonoid synthesis in chayote fruits was still unclear. In present study, a transcriptome analysis and metabolite profiling of chayote fruits at three different storage stages were conducted to explore the flavonoid compositions and gene expression associated with flavonoid synthesis. Through the UPLC-MS/MS analysis, a total of 57 flavonoid compounds were detected. Of these, 42 flavonoid glycosides were significantly differential accumulation in chayote fruits at three different storage stages. Many genes associated with flavonoid synthesis were differentially expressed in chayote fruits at three different storage stages through RNA-seq analysis, including structural genes and some TFs. There was a high correlation between RNA-seq analysis and metabolite profiling, and the expression level of candidate genes in the flavonoid synthesis pathway were consistent with the dynamic changes of flavonoids. In addition, one R2R3-MYB transcription factor, FSG0057100, was defined as the critical regulatory gene of flavonoid synthesis. Furthermore, we treated chayote fruits during storage with phenylalanine, and the results show exogenous phenylalanine applications might promote the flavonoid synthesis. Phenylalanine is a effective additive to maintain or improve the total content flavonoids in chayote fruit during storage, can apply the phenylalanine in the postharvest storage of chayote. The above results not only make us better understand the molecular mechanism of flavonoid synthesis in chayote fruits, but also contribute to the promotion and application of chayote products. Overall design: In present study,we here performed metabolome and transcriptome profiling of chayote fruits during storage at room temperature to examine the dynamic changes of flavonoid compounds and the corresponding regulatory mechanism of flavonoid synthesis. A total of 57 flavonoid derivatives were detected in this study. Among them, 42 flavonoid glycosides were differentially accumulated in different storage stages. Moreover, the DEGs, including structural genes and transcriptional factors (TFs) for flavonoid synthesis were also identified, and the expression pattern of some DEGs were further verified using qRT-PCR. Correlation analysis between RNA-seq analysis and metabolite profiling had revealed that the identified structural genes and TFs displayed better correlation with the quantitative changes of flavonoids.