Isolation and in silico analysis of a transcript variant for a putative terpene synthase (HbTPS6L-X1) from the bark tissues of rubber Hevea brasiliensis RRIV 209

Hevea brasiliensis is the only tree species grown to produce natural rubber. The method of harvesting latex by slicing a groove into the bark of the tree mimics a mechanical wounding. In addition, rubber trees could be frequently exposed to pest and pathogen attacks through the scraped bark region. Terpenoids are a group of specialised compounds that play an important role in plant-environment interactions, especially in plant response to stress factors. The diversity of terpenoids is mainly determined by enzymes of the terpene synthase (TPS) family. Screening the RNA-seq data of H. brasiliensis revealed the presence of many putative TPS genes expressed in the bark tissues of rubber trees; however, their function has not been studied. This paper presents the identification of a TPS gene transcript variant (designated as HbTPS6L-X1) from the bark tissues of H. brasiliensis RRIV 209. Through the analysis of the phylogenetic tree, the presence of conserved motifs, and the signal peptide sequence region of the protein, as well as structural homology to known sesquiterpene synthases from other plants, HbTPS6L-X1 was predicted to belong to the TPS-a subfamily, be localised in the cytoplasm and catalyse the conversion of farnesyl diphosphate (FPP) to sesquiterpenes. These in silico functional characteristics are the basis for designing experiments to confirm the in planta biological function of HbTPS6L-X1 protein.