Time-Series Gene Expression Analysis of Terpene Synthase Gene Family Reveals its Evolutionary Dynamics in a Tobacco Plant

Abstract Terpene is an important secondary metabolite during plant development. The gene family of terpene synthases (TPS) is in charge of producing thousands of different terpenes that can increase the environmental fitness of plant. Some types of terpene contribute aroma and flavor that influence consumer preferences in tobacco but the knowledge of the TPS genes encoded by local tobacco cultivars are limited. Here, a total of 186 TPS genes were identified by annotating the tobacco genome sequences. Phylogenetic analysis showed that a few tobacco-exclusive TPS clades emerged recently through gene duplication, which are likely to be responsible for a range of compounds that separate N. tabacum cultivars from its wild relatives. Transcriptome sequencing of two local cultivars at three developmental stages revealed that five TPS genes from the TPS-a and TPS-b lineages are constitutively expressed while other duplicated ones are only expressed at the time of harvest. Additionally, some TPS genes underwent alternative splicing, which further diversified the protein sequences of the TPS gene family. The expression diversity and the evolution dynamics of this important gene family highlighted its critical role in the plant of tobacco. Our study provided candidate gene target for future breeding improvement of this critical industrial crop.