Abstract
BACKGROUND: Terpenoids constitute a diverse group of primary and secondary metabolites that are extensively distributed in living organisms and play key roles in growth, development, and environmental adaptation. Terpenoids are derived from two isomeric precursors that are interconverted by isopentenyl-diphosphate delta-isomerase (IDI), in both the plastids and cytoplasm of plants. The plastidial pathway supplies precursors for diterpenoids and carotenoids, whereas the cytoplasmic pathway provides precursors for sesquiterpenoids and triterpenoids. A family of terpene synthases (TPSs) produce most terpenoids such as sesquiterpenes, hemiterpenes, monoterpenes, diterpenes and sesterterpenes, which in allotetraploid peanut (Arachis hypogaea L.) have been relatively underexplored. RESULTS: In this study, 77 AhTPS genes were identified in the peanut genome and phylogenetically classified into five subfamilies. These AhTPSs are organized in clusters across chromosomes and exhibit conserved gene structures and motifs within each subfamily. AhTPSs in the TPS-c and -e/f subfamilies, specifically copalyl diphosphate synthase (CPS) and kaurene synthase (KS), were localized to plastids through transient expression in Nicotiana benthamiana leaves. The expression of AhCPS3 was detected a significant increase in response to abscisic acid (ABA) and methyl jasmonate (MeJA), which was notably distinct from the expression patterns of other AhCPSs and AhKS. Furthermore, 12 terpenoids were identified during seed development. Module-trait correlation analysis disclosed that the expression levels of genes encoding AhCPSs (involved in diterpene biosynthesis) and phytoene synthases (AhPSYs, involved in carotenoid biosynthesis) were significantly correlated with the abundances of soyasaponins (triterpenoids) during seed development in peanut. Additionally, the gene encoding β-amyrin synthase (AhβAS), which produces the backbone of triterpenoids, was identified in a significant module and was also induced by ABA and MeJA. Protein-protein interaction networks indicated AhCPSs, AhPSYs, and AhβAS shared a common interacting protein, AhIDI. CONCLUSIONS: These findings provide valuable insights into the potential cross-talk in terpenoid biosynthesis across different cellular compartments.