Differences in volatile composition and expression of genes involved in terpenoids biosynthesis in Chrysanthemum indicum var. aromaticum

Abstract

Chrysanthemum indicum var. aromaticum is an important ornamental plant in the genus Chrysanthemum, known for its unique and intense aroma. However, little is known about the composition of aroma components and their molecular regulatory mechanisms, which limits the development and utilization of Ci. var. aromaticum. In this study, headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) were used to analyze the aroma components of different organs (stem, leaf, and flower in different stages) of Ci. var. aromaticum. Meanwhile, the relative expression levels of key genes of terpenoid metabolism in different organs were determined by real-time quantitative PCR (qRT-PCR). Results showed that, a total of 128 volatiles were detected in 5 organs of Ci. var. aromaticum with more than 88.99% of terpenoids proportion, and 38 of the 128 were characteristic aroma compounds. Among the characteristic aroma compounds, 13 of them, including β-eudesmol, β-caryophyllene, zingiberene, α-bergamotene, α-curcumene, germacrene D, δ-cadinene, γ-terpinene, β-bisabolene, α-cubebene, aromandendrene, alloaromadendrene, and eucalyptol, formed the main aroma of Ci. var. aromaticum, and it was suggested that β-caryophyllene, zingiberene, eucalyptol, β-eudesmol, β-pinene, α-muurolene, and isocaryophyllene were responsible for the difference in aroma between the different organs of Ci. var. aromaticum. Combined with metabolomics, it was inferred that terpenoids such as β-eudesmol, cis-sabinol, α-thujone, α-thujene, etc. were involved in mevalonate (MVA) pathway; β-phellandrene, α-copaene, etc. were involved in methylerythritol phosphate (MEP) pathway. This study provided some theoretical guidance for further exploration of the aroma mechanism of Ci. var. aromaticum, which was helpful to the fully development and utilization of Ci. var. aromaticum resources.