Elucidating the Secondary Metabolite Biosynthesis Networks in Underutilized Tree Bean (Parkia timoriana) Through Integrated Metabolomic and Transcriptomic Approaches.

Abstract

The tree bean (Parkia timoriana (DC). Merr) is an underutilized legume and is abundantly found in Southeast Asia. It is valued for its nutritious pods and cultivated for food and timber. Despite of the presence of several nutrients, the regulatory networks involved in secondary metabolite biosynthesis in the tree bean remain largely unexplored. Recent studies have highlighted that consumption of its pods provides numerous health benefits, including antioxidant, α-glucosidase inhibitory, antibacterial, antidiabetic, and insecticidal activities. To elucidate the biosynthesis of specific metabolites in this plant, a comparative metabolite and transcriptomic analysis of the leaf and root tissues of P. timoriana was carried out. The study revealed that P. timoriana leaf and root tissues contain varying levels of phenolics, flavonoids, and terpenoids. ¹H nuclear magnetic resonance (¹H NMR) analysis identified 16 significant metabolites in the leaf and root tissues, including sugars, amino acids, and organic acids. L-dihydroxyphenylalanine (L-DOPA), an amino acid derivative and precursor to dopamine, was detected for the first time in the seeds. Additionally, the presence of pinitol in P. timoriana was also confirmed. De novo RNA-sequence analysis identified differentially expressed genes (DEGs) in both the tissues. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis identified pathways associated with shikimate pathway, such as phenylpropanoid and flavonoid biosynthesis. MapMan pathway analysis revealed a high number of transcripts related to phenylalanine, tryptophan, tyrosine, and condensed tannin biosynthesis. The research conducted identified secondary metabolites in P. timoriana, and their probable biosynthetic pathway which can be used for medicinal and nutritional purposes.