Molecular characterization and phylogenetic analysis of kaurene synthase protein in Stevia rebaudiana MS007

Abstract

Stevia rebaudiana is a plant under the Asteraceae family and has been reported as a healthier alternative to sugar. Steviol glycosides (SGs) is the group of secondary metabolites responsible for the sweet taste. Among nine SGs synthesised by S. rebaudiana, stevioside and rebaudioside A are the sweetest. The biosynthetic pathway of SGs partly involves conversion of geranylgeranyl diphosphate (GGDP) into steviol, catalysed by ent- kaurene synthase (KS), ent-copalyl diphosphate synthase (CPPS), and kaurene oxidase (KO). This study focuses on in silico molecular characterization and phylogenetic analysis of KS from Malaysia’s S. rebaudiana MS007 variety (Stevia MS007). The transcriptomic dataset of S. rebaudiana accession MS007 was used in initial experiment toward analysing the KS. Through the blastx homology search using transcriptomic dataset query Cluster-31069.42907, the Stevia rebaudiana kaurene synthase (SrKS) sequence was identified with the highest similarity percentage identity (99.62%). The protein domain prediction using InterPro yields IPR005630 (terpene synthase metal-binding domain) at positions 490 to 755 and IPR001906 (terpene synthase-N-terminal-domain) at positions 258 to 477. Multiple sequence alignment was conducted using MUSCLE and MEGA-X as phylogenetic tree analysis tool for constructing the phylogenetic analysis tree. Based on the bootstrap value from the phylogenetic analysis, Cluster-31069.42907 represents relationships between the ancestors. Since both Helianthus annuus and S. rebaudiana are Asteraceae species, the bootstrap value for both species was 100%. In conclusion, this research contributes to a better understanding of Stevia MS007 KS via in silico analysis.