Systematic analysis of TPS genes for the synthesis of floral aroma components of Gardenia jasminoides J. Ellis based on the whole genome

Gardenia jasminoides J. Ellis flowers are white in color and have a pleasant aroma. These flowers have high ornamental value and are an important source of natural spices. Terpenes are the main components of the unique aroma of G. jasminoides flowers, but the key terpene synthases (TPSs) for the biosynthesis of such volatile products have not yet been identified. Here, based on the high-quality genome of G. jasminoides, this study comprehensively explored the TPS genes related to floral scent biosynthesis through transcriptomic, phylogenetic, and conserved domain analysis. In total, 44 GjTPS genes were identified in G. jasminoides, unevenly distributed on 11 chromosomes, and nine GjTPS genes participated in tandem duplication events. All GjTPSs were clustered into five subfamilies, 27 of which belonged to the angiosperm-specific clades, including TPS-a, TPS-b, and TPS-g. Combining transcriptomic data and quantitative real-time PCR (qRT-PCR) analyses of five organs, five candidate GjTPS genes, with high expression in blooming flowers and containing the active motif DDXXD and NSE/DTE, were screened. Among them, GjTPS1, GjTPS2, GjTPS3, and GjTPS27 were grouped in the TPS-b clade, speculated to be the TPSs responsible for the biosynthesis of the main floral aroma components of G. jasminoides, such as linalool and ocimene, while GjTPS18 from the TPS-a clade may be a farnesene synthase.