Identification of OjGBS, a terpene synthase involved in germacrene B biosynthesis in Oenanthe javanica

Water dropwort is a perennial herb with distinctive aroma in Apiaceae family. Terpenoids are the dominant components of volatile compounds in water dropwort. In this study, germacrene B was identified as a unique terpenoid in ‘Liyang Baiqin’ compared to ‘Fuqin No. 1’, based on comparative GC-MS analysis of their terpene profiles. The transcriptome of ‘Liyang Baiqin’ was analyzed using the genome of ‘Fuqin NO. 1’. A total of 3139 novel genes and 36,500 novel transcripts were identified by sequence comparison, in which 288 novel transcripts were enriched in metabolism of terpenoids and polyketides. In methylerythritol phosphate (MEP) and mevalonate (MVA) pathways, a total of 63 structural genes were identified. OjGBS was identified as a novel terpene synthase in ‘Liyang Baiqin’. OjGBS was highly expressed in petioles of water dropwort. According to the evolutionary relationships, OjGBS was categorized into the TPS-a subfamily. The conserved domains of Class Ⅰ, DDxxD and NSE/DTE motifs, were identified in OjGBS protein. Enzyme activity assay suggested that substrate farnesyl diphosphate (FPP) was converted into germacrene B in vitro under the catalysis of OjGBS. Overexpression of OjGBS in Arabidopsis thaliana promoted the accumulation of germacrene B. These findings collectively advance the molecular understanding of cultivar-specific terpenoid biosynthesis and identification of new functional OjTPS s in water dropwort. • The terpene profiles of ‘Liyang Baiqin’ and ‘Fuqin NO.1’ were compared. • The unique terpene synthase OjGBS in ‘Liyang Baiqin’ participated in the synthesis of germacrene B. • The purified OjGBS protein catalyzed the synthesis of germacrene B in vitro . • Overexpression of OjGBS in transgenic plants generated amounts of germacrene B.