Switchgrass metabolomics reveals striking genotypic and developmental differences in specialized metabolic phenotypes

Abstract

Title: Switchgrass metabolomics reveals striking genotypic and developmental differences in 3 saponins 4 Abstract 38Switchgrass (Panicum virgatum L.) is a bioenergy crop that grows productively on low-fertility 39 lands not suitable for food production. We hypothesize that traits such as low soil nitrogen 40 demand, tolerance to water limitation and resistance to insect pests and microbial pathogens are 41 influenced by low molecular weight compounds known as specialized metabolites. We leveraged 42 untargeted liquid chromatography-mass spectrometry (LC-MS) and quantitative gas 43 chromatography-mass spectrometry (GC-MS) to identify differences in above-and below-44 ground metabolomes of three northern upland and three southern lowland switchgrass cultivars. 45This analysis documented abundant steroidal saponins and terpenoid glycosides as well as varied 46 phenolic compounds in switchgrass extracts. We identified many metabolite 'features' 47 set the stage for testing the impacts of differentially accumulating metabolites on biotic and 53 abiotic stress tolerance and inform development of low-input bioenergy crops. 54 55 56 57 58 59 60 61 62 63 64 4 65

Comparative transcriptomics and metabolomics reveal specialized metabolite drought stress responses in switchgrass (Panicum virgatumL.)

“…Contrasting the largely unaltered and comparable expression of the highly conserved upstream pathway genes, both Alamo and Cave-in-Rock plants featured distinct gene expression profiles for downstream pathway branches that generate species-specific, functionalized metabolites. Following the recent discovery of specialized triterpenoid and steroid saponins in switchgrass (Li et al 2020), identification and gene expression analysis of predicted cycloartenol synthases ( CAS ), lanosterol synthases ( LAS ), β-amyrin synthases ( BAS ), as well as members of the CYP71A , CYP90B and CYP94D cytochrome P450 families and sterol 3-β-glucosyltransferases with known functions in triterpenoid metabolism revealed distinct expression patterns across tissue type and genotype (Fig. 4).…”

“…Metabolite analysis followed previously established protocols (Li et al (2020). Here, 100 mg tissue were ground to a fine powder in liquid N 2 and metabolites were extracted with 1 ml 80% methanol containing 1 μM telmisartan internal standard by vortexing briefly and incubation for 16 h at 200 rpm and 4°C.…”

“…Following the recent discovery of specialized triterpenoid and steroid saponins in switchgrass (Li et al 2020), identification and gene expression analysis of predicted cycloartenol synthases (CAS), lanosterol synthases (LAS), b-amyrin synthases (BAS), as well as members of the CYP71A, CYP90B and CYP94D cytochrome P450 families and sterol 3-β-glucosyltransferases with known functions in triterpenoid metabolism revealed distinct expression patterns across tissue type and genotype (Fig. 4).…”

Getting back to the grass roots: harnessing specialized metabolites for improved crop stress resilience

“…1) [43]. Recent analyses further demonstrate that steroidal (C27) saponins and terpenoid glycosides derived from diosgenin, oxydiosgenin and anhydrodiosgenin sapogenin cores can predominate in switchgrass roots [44].…”

Cytochrome P450‐catalyzed biosynthesis of furanoditerpenoids in the bioenergy crop switchgrass (Panicum virgatum L.)

“…Panicum virgatum (switchgrass) is a key species of the North American tallgrass prairie ecosystem and is valued as a forage and biofuel crop for its high net energy yield and abiotic stress tolerance (Liu et al, 2015;Lovell et al, 2021;Schmer et al, 2008). Broad drought-induced alterations in carbohydrate, lipid, phenylpropanoid and terpenoid metabolism support a role of specialized metabolites in switchgrass abiotic stress resilience (Li et al, 2021;Meyer et al, 2014;Muchlinski et al, 2019;Pelot et al, 2018). Diterpenoids in monocot crops almost invariably belong to the group of labdane-related metabolites, and feature species-specific structures, bioactivities, and spatiotemporal regulation and distribution (Murphy and Zerbe, 2020;Schmelz et al, 2014;Zi et al, 2014).…”