Switchgrass (Panicum virgatum L.) is a bioenergy crop that grows productively on lands not suitable for food production and is an excellent target for low-pesticide input biomass production. We hypothesize that resistance to insect pests and microbial pathogens is influenced by low-molecular-weight compounds known as specialized metabolites. We employed untargeted liquid chromatography–mass spectrometry, quantitative gas chromatography–mass spectrometry (GC–MS), and nuclear magnetic resonance spectroscopy to identify differences in switchgrass ecotype metabolomes. This analysis revealed striking differences between upland and lowland switchgrass metabolomes as well as distinct developmental profiles. Terpenoid- and polyphenol-derived specialized metabolites were identified, including steroidal saponins, di- and sesqui-terpenoids, and flavonoids. The saponins are particularly abundant in switchgrass extracts and have diverse aglycone cores and sugar moieties. We report seven structurally distinct steroidal saponin classes with unique steroidal cores and glycosylated at one or two positions. Quantitative GC–MS revealed differences in total saponin concentrations in the leaf blade, leaf sheath, stem, rhizome, and root (2.3 ± 0.10, 0.5 ± 0.01, 2.5 ± 0.5, 3.0 ± 0.7, and 0.3 ± 0.01 μg/mg of dw, respectively). The quantitative data also demonstrated that saponin concentrations are higher in roots of lowland (ranging from 3.0 to 6.6 μg/mg of dw) than in upland (from 0.9 to 1.9 μg/mg of dw) ecotype plants, suggesting ecotypic-specific biosynthesis and/or biological functions. These results enable future testing of these specialized metabolites on biotic and abiotic stress tolerance and can provide information on the development of low-input bioenergy crops.

中文翻译：

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柳枝稷代谢组学揭示了特殊代谢表型的显着基因型和发育差异


柳枝稷 ( Panicum virgatum L.) 是一种生物能源作物，可在不适合粮食生产的土地上高效生长，是低农药投入生物质生产的绝佳目标。我们假设对害虫和微生物病原体的抵抗力受到称为特殊代谢物的低分子量化合物的影响。我们采用非靶向液相色谱-质谱、定量气相色谱-质谱（GC-MS）和核磁共振波谱来识别柳枝稷生态型代谢组的差异。该分析揭示了高地和低地柳枝稷代谢组之间的显着差异以及不同的发育概况。鉴定出萜类化合物和多酚类化合物衍生的专门代谢物，包括甾体皂苷、二萜类化合物和倍半萜类化合物以及类黄酮。柳枝稷提取物中的皂苷含量特别丰富，并且具有多种苷元核心和糖部分。我们报告了七种结构不同的甾体皂苷类，具有独特的甾体核心并在一个或两个位置糖基化。定量 GC-MS 显示叶片、叶鞘、茎、根茎和根中总皂苷浓度存在差异（2.3 ± 0.10、0.5 ± 0.01、2.5 ± 0.5、3.0 ± 0.7 和 0.3 ± 0.01 μg/mg 干物质） ， 分别）。定量数据还表明，低地生态型植物根部的皂苷浓度（范围为 3.0 至 6.6 μg/mg 干重）高于高地生态型植物根部（范围为 0.9 至 1.9 μg/mg 干重），这表明生态型特异性生物合成和/或生物功能。这些结果使得未来能够测试这些专门代谢物对生物和非生物胁迫耐受性的影响，并可以提供有关低投入生物能源作物开发的信息。