Co-Analysis of Metabolomics and Transcriptomics Reveals Key Pathways and Genes Associated with Pigment and Flavonoid Regulation in Mint

Abstract

: Mint is notably rich in phenolic acids, flavonoids, antioxidants and other bioactive components, and is widely used as food, medicine, spices, and flavoring agents. Thus, metabolite composition serves as a critical indicator for assessing mint quality. In this study, two mint genotypes of Mentha canadensis L., were sampled, namely purple mint and green mint. The two genotypes are distinguished by stem color: the purple mint exhibits purple stems, whereas the green mint has green stems. The purple mint exhibited significantly higher anthocyanin and total flavone contents than green mint. Integrated transcriptomic and metabolomic analyses were performed to elucidate the regulatory mechanisms underlying pigment and flavonoid accumulation in mint stems. High-throughput RNA-Seq yielded 167,901 unigenes, of which 34,608 genes were differentially expressed. These differentially expressed genes (DEGs) were mainly involved in the lignin metabolic process and flavonoid biosynthetic process. A total of 143 differentially expressed metabolites (DEMs) were enriched in isoflavonoid, flavonoid biosynthesis, flavone and flavonol biosynthesis, and anthocyanin biosynthesis pathways. Co-analysis of DEGs and DEMs revealed that the flavone and flavonol biosynthesis pathway (ko00944) contained the most DEMs, followed by the flavonoid biosynthesis pathway (ko00941) and the anthocyanin biosynthesis pathway (ko00942). Furthermore, nine key genes and metabolites were identified using the O2PLS model. These findings provide a theoretical basis for understanding the key pathways and genes involved in pigment and flavonoid regulation in mint stems.