The foxtail millet (Setaria italica) terpene synthase gene family

Abstract

SUMMARY Terpenoid metabolism plays vital roles in stress defense and the environmental adaptation of monocot crops. Here, we describe the identification of the terpene synthase (TPS) gene family of the panicoid food and bioenergy model crop foxtail millet (Setaria italica). The diploid S. italica genome contains 32 TPS genes, 17 of which were biochemically characterized in this study. Unlike other thus far investigated grasses, S. italica contains TPSs producing all three ent‐, (+)‐ and syn‐copalyl pyrophosphate stereoisomers that naturally occur as central building blocks in the biosynthesis of distinct monocot diterpenoids. Conversion of these intermediates by the promiscuous TPS SiTPS8 yielded different diterpenoid scaffolds. Additionally, a cytochrome P450 monooxygenase (CYP99A17), which genomically clustered with SiTPS8, catalyzes the C19 hydroxylation of SiTPS8 products to generate the corresponding diterpene alcohols. The presence of syntenic orthologs to about 19% of the S. italica TPSs in related grasses supports a common ancestry of selected pathway branches. Among the identified enzyme products, abietadien‐19‐ol, syn‐pimara‐7,15‐dien‐19‐ol and germacrene‐d‐4‐ol were detectable in planta, and gene expression analysis of the biosynthetic TPSs showed distinct and, albeit moderately, inducible expression patterns in response to biotic and abiotic stress. In vitro growth‐inhibiting activity of abietadien‐19‐ol and syn‐pimara‐7,15‐dien‐19‐ol against Fusarium verticillioides and Fusarium subglutinans may indicate pathogen defensive functions, whereas the low antifungal efficacy of tested sesquiterpenoids supports other bioactivities. Together, these findings expand the known chemical space of monocot terpenoid metabolism to enable further investigations of terpenoid‐mediated stress resilience in these agriculturally important species.

Crosstalk between phytohormones and secondary metabolites in the drought stress tolerance of crop plants: A review

“…TERPENE SYNTHASES ( TPS ) are involved in terpene biosynthesis. Drought conditions stimulate these TPS genes in various plants, such as pearl millet and tea plants (Karunanithi et al, 2020; Zhou, Shamala, et al, 2020). In a study on lemongrass, SA‐application ameliorates drought stress and induces terpene citral level (Idrees et al, 2010).…”

Furanoditerpenoid biosynthesis in the bioenergy crop switchgrass is catalyzed by an alternate metabolic pathway

“…Particularly, knowledge of the dynamic networks of plant specialized metabolites that enable plants to adapt to environmental pressures is needed in light of exacerbating crop losses caused by climate shifts and associated pest and disease damage (Savary et al, 2019). Diterpenoids serve as key components of biotic and abiotic stress resilience in rice and maize (Schmelz et al, 2014; Murphy and Zerbe, 2020), and stress-inducible, speciesspecific diterpenoid networks have also been discovered in other food and bioenergy crops such as switchgrass, foxtail millet and wheat, although their physiological functions are less well understood (Wu et al, 2012; Zhou et al, 2012; Schmelz et al, 2014; Pelot et al, 2018; Ding et al, 2019; Karunanithi et al, 2020). Prior studies identified an expansive diTPS gene family in allotetraploid switchgrass that forms specialized diterpenoids both common among the grass family and, to current knowledge, uniquely present in switchgrass (Pelot et al, 2018).…”

Systematic Analysis of the Lysine Malonylome in Sanghuangporus Sanghuang

“…Further modi cation of terpenes involves the introduction of acyl, aryl, or glycosyl groups, usually starting with oxidation catalysed by cytochrome P450 monooxygenases (P450s, also known as CYPs). P450s are ubiquitous in nature and are involved in fundamental biological pathways such as terpene biosynthesis [43][44][45][46]. All these key enzymes were detected by malonyl-enriched modi cations.…”