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

Several specialized terpenoids that are used as phytoalexins are produced in the plant of tobacco. They play a key role in plant defense against pests and pathogens. Here, we performed genome-wide identification, classification, and expression profiling of the terpene synthase (TPS) genes in the tobacco genome. A total of 186 TPS genes were identified, which is significantly higher than that in wild Nicotiana, Capsicum and Solanum species. Phylogenetic analysis of these TPS genes in tobacco and Solanaceous relatives as well as Arabidopsis showed that a few tobacco-exclusive TPS clades occurred recently through gene duplication events. These clades are likely to be responsible for a range of compounds that separate N. tabacum cultivars from its wild relatives. Transcriptome sequencing of two cultivars of N. tabacum at several developmental stages revealed that some TPS genes from the TPS-a and TPS-b lineages are constitutively expressed and a few duplicated TPS genes are only expressed post anthesis at the time of harvest. Additionally, some TPS genes underwent alternative splicing, further diversifying the gene products of the TPS genes. Our findings provide an important candidate genes for further understanding of the diversity and evolution as well as functionality of TPS genes in the plant of tobacco.