Comparative metabolomics provides novel insights into the basis of petiole color differences in celery (Apium graveolens L.)

Abstract

Plant metabolites are important for plant development and human health. Plants of celery (Apium graveolens L.) with different-colored petioles have been formed in the course of long-term evolution. However, the composition, content distribution, and mechanisms of accumulation of metabolites in different-colored petioles remain elusive. Using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), 1159 metabolites, including 100 lipids, 72 organic acids and derivatives, 83 phenylpropanoids and polyketides, and several alkaloids and terpenoids, were quantified in four celery cultivars, each with a different petiole color. There were significant differences in the types and contents of metabolites in celery with different-colored petioles, with the most striking difference between green celery and purple celery, followed by white celery and green celery. Annotated analysis of metabolic pathways showed that the metabolites of the different-colored petioles were significantly enriched in biosynthetic pathways such as anthocyanin, flavonoid, and chlorophyll pathways, suggesting that these metabolic pathways may play a key role in determining petiole color in celery. The content of chlorophyll in green celery was significantly higher than that in other celery cultivars, yellow celery was rich in carotenoids, and the content of anthocyanin in purple celery was significantly higher than that in the other celery cultivars. The color of the celery petioles was significantly correlated with the content of related metabolites. Among the four celery cultivars, the metabolites of the anthocyanin biosynthesis pathway were enriched in purple celery. The results of quantitative real-time polymerase chain reaction (qRT-PCR) suggested that the differential expression of the chalcone synthase (CHS) gene in the anthocyanin biosynthesis pathway might affect the biosynthesis of anthocyanin in celery. In addition, HPLC analysis revealed that cyanidin is the main pigment in purple celery. This study explored the differences in the types and contents of metabolites in celery cultivars with different-colored petioles and identified key substances for color formation. The results provide a theoretical basis and technical support for genetic improvement of celery petiole color.

摘要

目的

对四种不同颜色芹菜的呈色物质进行比较分析, 探讨芹菜叶柄颜色形成的机理。

创新点

明确了芹菜叶柄颜色形成的主要差异代谢物的调控途径。

方法

以四个叶柄颜色差异明显的芹菜品种(白色、黄色、绿色和紫色)为材料, 利用非靶代谢组学分析, 探讨了叶柄的代谢物成分, 对四个品种的花青素、叶绿素、类胡萝卜素含量进行测定, 研究不同品种富含的代谢物进而探讨不同颜色形成的机理, 进一步运用高效液相色谱技术(HPLC)进行代谢物验证, 并结合基因表达揭示了芹菜叶柄颜色呈色的差异代谢物调控途径。

结论

不同颜色芹菜叶柄中叶绿素、花青素、类胡萝卜素含量差异显著, 花青素和叶绿素分别在紫色和绿色品种中大量积累, 表明花青素与叶绿素可能在芹菜叶柄颜色中起关键作用。利用非靶代谢组学在四个品种中检测到647种差异代谢物, 不同颜色芹菜代谢物质种类和含量存在显著差异, 绿色芹菜富含与叶绿素生物合成途径相关的代谢物, 紫色芹菜富含与花青素生物合成途径的代谢物。进一步采用HPLC验证显示矢车菊素是紫芹的主要色素。为探究代谢物和基因表达的相关性, 采用实时定量聚合酶链反应(qRT-PCR)进行表达量分析, 结果与代谢物积累趋势一致。此外, 不同颜色的芹菜富含不同的营养物质, 例如, 具有生物活性的代谢物如芹菜素和儿茶素被发现在绿芹中显著富集。本研究鉴定出丰富的代谢产物不仅为研究芹菜的生物活性物质提供了信息, 也为挖掘不同颜色植物的代谢产物提供参考。