Biochemical Characterization and Function of Eight Microbial Type Terpene Synthases from Lycophyte _Selaginella moellendorffii_  
[PERSON]  
1 Key Laboratory of Ministry of Education for Medicinal Plant Resource and Natural Pharmaceutical Chemistry, College of Life Sciences, Shaarxi Normal University, Xi'an 710119, Shaarxi, China; [EMAIL_ADDRESS] (Y.Z.); [EMAIL_ADDRESS] (T.H.); [EMAIL_ADDRESS] (R.L.); [EMAIL_ADDRESS] (Z.H.); [EMAIL_ADDRESS] (G.L.)  
[PERSON]  
1 Key Laboratory of Ministry of Education for Medicinal Plant Resource and Natural Pharmaceutical Chemistry, College of Life Sciences, Shaarxi Normal University, Xi'an 710119, Shaarxi, China; [EMAIL_ADDRESS] (Y.Z.); [EMAIL_ADDRESS] (T.H.); [EMAIL_ADDRESS] (R.L.); [EMAIL_ADDRESS] (Z.H.); [EMAIL_ADDRESS] (G.L.)  
[PERSON]  
1 Key Laboratory of Ministry of Education for Medicinal Plant Resource and Natural Pharmaceutical Chemistry, College of Life Sciences, Shaarxi Normal University, Xi'an 710119, Shaarxi, China; [EMAIL_ADDRESS] (Y.Z.); [EMAIL_ADDRESS] (T.H.); nxiqliu@snu.  
were initially identified in the genome of the lycopbyte _Selaginella moellendorffii_, from whose 48 _MTPSL_ genes were identified [12]. It was found that the genome of _S. moellendorffii_ existed two kinds of _TPS_ genes. The first kind was designated as _S. moellendorffii_ TPS genes (_SmTPSs_), consisting of 18 members. The second kind was designated as _S. moellendorffii_ microbial _TPS_-like genes (_SmMTPSLs_), consisting of 48 members [12]. Phylogenetic analysis indicated that SmTPSs were very closely related to typical seed plant TPSs while SmMTPSLs were more similar to microbial TPSs, in particular fungal TPSs [12]. Meanwhile, it had been proved that several representative SmTPSs encoded diterpene syntheses while representative SmMTPSLs encoded monoterpene and sesquiterpene synthases [12]. In addition to the six _MTPSL_ genes biochemically characterized from _S. moellendorffii_[12], _MTPSLs_ have been successively characterized in other species, including liverworks [13], ferns [14], red algae [15], hornwords [16], and mosses [10].  
Despite increasing knowledge of the anatomical and biochemical processes of induced terpenoid defenses in _S. moellendorffii_, detailed molecular and biochemical dissection of these complex defense systems is currently limited by lack of identification and functional characterization of the _SmMTPSL_ genes involved. Six _SmMTPSL_ genes were characterized in a previous study [12]. However, most _SmMTPSL_ genes, their particular biochemical functions and their contribution to chemical defense remain to be discovered and functionally characterized. In the present study, we sequentially characterized another eight _SmMTPSL_ genes to investigate their biological functions in nonseed plants. First, these eight full-length _SmMTPSL_ genes were identified by analyzing the available genomic and transcriptomic resources from _S. moellendorffii_. Next, we analyzed the phylogenetic relatedness of eight _SmMTPSL_ genes with other known _MTPSLs_. Furthermore, in vitro biochemical characterization were performed, suggesting that SmMTPSLs display monoterpene synthase and sesquiterpene synthase activities. In addition, expression analysis of three _SmMTPSL_ genes showed that SmMTPSLs in _S. moellendorffii_ is responsible for the biosynthesis of stress-induced terpenoids. Lastly, it had been demonstrated that the enzymatic products of SmMTPSLs have an anti-bacterial activity in vitro.