Genome-wide identification and functional characterization of trans-IDS genes give new insights into terpene biosynthesis in Syringa oblata

Floral scents play a vital role in plant pollination and ornamental plant industry. Syringa oblata, a typical aromatic and medicinal plant, holds a high terpene concentration as the main fragrant volatiles and plays a crucial role in the breeding in the Syringa genus. The trans-isopentenyl diphosphate synthases (trans-IDSs) were critical enzymes in terpenoid diversity and accumulation. However, genome-wide characterization and systematic analysis of the lilac trans-IDS family are still under-explored. In this study, we identified sixteen trans-IDS genes belonging to five subfamilies on 10 chromosomes of the lilac genome. Each subfamily shared similar exon, intron, and motif distributions. Synteny analysis suggested that the lilac trans-IDS gene family expanded through segmental and tandem duplication events. We also analyzed their expression levels in various organs and flower development stages for terpene biosynthesis functional insights. Furthermore, spatiotemporal gene expression, virus-induced gene silencing (VIGS), transient overexpression, and transgenic Arabidopsis results collectively showed SoGPPS2 enhances terpene volatile synthesis. SoGPPS2 also impacted plant growth and flowering. And potential upstream transcription regulatory networks for SoGPPS2 were identified. In summary, this study enhances our comprehensive understanding of the lilac trans-IDS gene family for the first time, providing crucial insights into terpene synthesis and laying the groundwork for future floral aromatic breeding, medicinal and essential oil industries in lilac.