Genome-wide identification and expression analysis of terpene synthase gene family in Aquilaria sinensis

Agarwood is the resinous portion of Aquilaria trees, and has been widely used as medicine and incense. Sesquiterpenes are the main chemical characteristic constituents of agarwood. Terpene synthase (TPS) is a critical enzyme responsible for biosynthesis of sesquiterpene compounds. However, limited information is available on genome-wide identification and characterization of the TPS family in Aquilaria trees. In this study, TPS gene family was identified and characterized in Aquilaria sinensis by bioinformatics methods. The expression of those genes was analyzed by RNA-seq and quantitative real-time PCR. Transcription factors regulating TPS gene expression were identified by yeast one-hybrid and dual-luciferase assay. In total, 26 AsTPS genes (AsTPS1-AsTPS26) were identified, which were classified into five subgroups. Many putative cis-elements putatively involved in stresses and phytohormones (especially jasmonic acid) were identified in the promoter regions of AsTPSs, suggesting that AsTPSs genes may be regulated by stresses and jasmonic acid. Expression analysis revealed seven TPS genes encoding sesquiterpene synthetases were induced by wounding and methyl jasmonic acid (MeJA), which may be related to sesquiterpene biosynthesis. By yeast one-hybrid screening, a ERF transcription factor AsERF1 was identified to interact with the AsTPS1 promoter. Subcellular localization analysis indicated AsERF1 was a nucleus-localized protein. Transient transfection of AsERF1 in leaves of Nicotiana benthamiana significantly enhanced the promoter activation of AsTPS1, suggesting AsERF1 may participate in sesquiterpene biosynthesis by regulating AsTPS1 expression. These data generated in this study provide a foundation for future studies on functional roles and regulation mechanisms of AsTPS in sesquiterpene biosynthesis and agarwood formation.