Fatty acid desaturase 2 (FAD2) is functionally involved in regulation of synthesis of fatty acid derivatives in Chrysanthemum indicum var. aromaticum.

The fatty acid desaturase 2 (FAD2) is an important functional gene in the fatty acid metabolism pathway of aromatic plants, which can significantly affect the biosynthesis of volatile compounds and the aroma characteristics. However, the possible mechanism of action of FAD2 in Chrysanthemum indicum var. aromaticum (Ci. var. aromaticum) is still unclear at present. In this study, the open reading frame (ORF) sequence of FAD2 (CiFAD2) was cloned from Ci. var. aromaticum, and it was heterologously transferred into the model plant tobacco by constructing a plant expression vector for overexpression. Then, the changes of volatiles content and species in the leaves of transgenic tobacco overexpressing CiFAD2 were analyzed by headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). Results showed that compared with wild-type (WT) and empty vector (EV) tobacco, tobacco plants overexpressing CiFAD2 had a slightly delayed flowering time, darker leaf color, and smaller leaf area; the contents of terpenes increased as well as the types of alcohols and aldehydes, and new ketones were detected. Quantitative real-time PCR (qRT-PCR) results showed that the expression levels of key enzyme genes (ADH, AOS, KCS) in the fatty acid metabolic pathway in transgenic tobacco were all increased. This study provided data support for the potential role of CiFAD2 in the biosynthesis process of volatile/aroma compounds in Ci. var. aromaticum, which may be applicable for cultivating new types of chrysanthemum varieties with aromatic characteristics.