DataSheet_12_Transcriptomics–metabolomics joint analysis: New highlight into the triterpenoid saponin biosynthesis in quinoa (Chenopodium quinoa Willd.).csv

Quinoa (Chenopodium quinoa Willd.) contains various physiologically active substances, including vitamins, polyphenols, flavonoids, phytosterols, and saponins. Research showed that saponins were the protective substances in the outer layer of quinoa seeds to defend against microbes, herbivores, and insects. Because the aglycones of quinoa saponins are triterpenoids, they are called triterpenoid saponins (TSs). In addition, the presence of TS imparted bitterness in quinoa and resulted in anticancer and anti-inflammatory effects. In this study, the seeds of low-saponin quinoa, NT376-2 (N), and high-saponin quinoa, B-12071(B), at 30 and 60 days after flowering (DAF) were used to measure the TS content and evaluated for their transcriptomic and metabolomic profiles. The amounts of TS were found to significantly differ between all possible comparisons: N and B at 30 DAF (N1_vs_B1), N and B at 60 DAF (N2_vs_B2), N at 30 DAF and 60 DAF (N1_vs_N2), and B at 30 DAF and 60 DAF (B1_vs_B2). RNA sequencing (RNA-seq) was used to screen differentially expressed genes (DEGs) and revealed 14,703 upregulated DEGs and 26,267 downregulated DEGs in the four comparison groups. The 311 overlapping DEGs found in the four comparisons were used for Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses to screen for DEGs related to TS biosynthesis in quinoa. Metabolomics analysis identified acetyl-CoA, 1-hydroxy-2-methyl-2-butenyl-4-diphosphate, farnesal, and (S)-2,3-epoxysqualene as the key differentially accumulated metabolites (DAMs). Transcriptomics–metabolomics joint analysis showed that triterpenoid biosynthesis and terpenoid backbone biosynthesis were the enriched pathways of TS biosynthesis; farnesal were the key DAMs shared in the four comparison groups and associated with 10 key candidate DEGs related to TS biosynthesis in quinoa. These results provided important references for in-depth research on the metabolic mechanism of TS in quinoa.

藜麦（Chenopodium quinoa Willd.）含有多种生理活性物质，包括维生素、多酚、黄酮类、植物甾醇与皂苷。研究表明，皂苷是藜麦种子外层抵御微生物、草食动物与昆虫的保护性物质。由于藜麦皂苷的苷元为三萜类化合物，因此这类皂苷被称为三萜皂苷（triterpenoid saponins, TSs）。此外，三萜皂苷的存在赋予藜麦苦味，同时具备抗癌与抗炎活性。本研究选取开花后30天（days after flowering, DAF）与开花后60天的低皂苷藜麦NT376-2（记为N）以及高皂苷藜麦B-12071（记为B）的种子，测定其三萜皂苷含量，并对其转录组与代谢组特征进行分析。所有对比组的三萜皂苷含量均存在显著差异：开花后30天的N与B组（N1_vs_B1）、开花后60天的N与B组（N2_vs_B2）、开花后30天与60天的N组（N1_vs_N2），以及开花后30天与60天的B组（B1_vs_B2）。本研究采用RNA测序（RNA-seq）筛选差异表达基因（differentially expressed genes, DEGs），在四个对比组中共鉴定出14703个上调差异表达基因与26267个下调差异表达基因。从四个对比组中筛选得到的311个共有差异表达基因，被用于基因本体（Gene Ontology, GO）与京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）富集分析，以挖掘与藜麦三萜皂苷生物合成相关的差异表达基因。代谢组分析鉴定出乙酰辅酶A、1-羟基-2-甲基-2-丁烯基-4-二磷酸、法尼醛以及(S)-2,3-环氧鲨烯作为关键差异积累代谢物（differentially accumulated metabolites, DAMs）。转录组与代谢组联合分析显示，三萜类生物合成与萜类骨架生物合成是藜麦三萜皂苷生物合成的富集通路；法尼醛是四个对比组共有的关键差异积累代谢物，且与10个参与藜麦三萜皂苷生物合成的关键候选差异表达基因相关。本研究结果为深入解析藜麦三萜皂苷的代谢调控机制提供了重要参考依据。