Integrative transcriptomic and metabolomic analysis reveals NBS resistance genes and metabolic pathways of Panax japonicus var. major

Panax japonicus var. major (PJ) is a valuable traditional Chinese medicinal plant that belongs to the Panax genus. Numerous studies have been conducted on the other Panax species, but only a limited number of studies have investigated the transcriptome and metabolome of PJ. Here, we analysed the transcriptome and metabolome from roots, stems, fruits, and leaves of PJ. A total of 507 plant defense-related nucleotide binding site (NBS) genes were identified, this result showed that PJ has the highest number of NBS genes compared with the other Panax species. Which indicated that NBS gene family has expanded in PJ, may be the key reason for stronger disease resistance of PJ. Moreover, 59 candidate genes involved in upstream pathways of saponins biosynthesis, 311 cytochrome P450 genes, and 147 UDP-dependent glycosyltransferase genes were identified, which were highly expressed in roots and leaves. Additionally, we also detected 1161 metabolites and 792 differentially accumulated metabolites, especially in leaves, fruits, and roots. Transcriptome, metabolome and RT-qPCR identified three UGT genes that could regulate triterpene saponin biosynthesis. This research will enhance our knowledge of saponins biosynthesis and disease resistance breeding of PJ.