## 2 Results
### Structure Models and Molecular Docking of SmMTPSLs  
To understand the structural basis underlying the functional divergence of SmMTPSLs, the structure models of eight SmMTPSL proteins were constructed using the I-TASSER Server. The Discovery Studio (DS) software was used to evaluate and score to select the best model, which was used for molecular docking, subsequently (Figure 3A). To predict the most stable pattern and active pocket of receptor-ligand binding, we performed SmMTPSLs molecular docking analysis with FPP and GPP by the DS software (Figure 3 and Figures S2-S8). The active pocket of receptor-ligand binding was highlighted in the red circle (Figure 3A). With semi-flexible docking, different conformations of ligand binding to the receptor produced a variety of docking results, and the group with the highest CDOCK score was selected as the best combination [18].  
Figure 1: Amino acid sequence alignment of microbial terpene synthase-like proteins (MTPSLs). The Asp-rich ‘DDxxD’ motif and the ‘NSD/DTE’ motif, which were involved in metal-dependent ionization of the isoprenyl diphosphate substrate and conserved among all SmMTPSLs, are shown.  
Taking SmMTPSL19 as an example, 17 amino acids had a mutual force with FPP according to the two-dimensional plan of docking (Figure 3B). Among them, amino acids K238, R321, and D93 with substrate FPP formed stable hydrogen bonds, which could help FPP find the entrance to the active site cavity and make the binding of ligand and receptor more stable. The Lys at 238 site and Arg at 321 site formed hydrogen bonds with oxygen atoms of FPP phosphate group, the Asp at 93 site formed hydrogen bonds with hydrogen atoms of FPP phosphate group. Besides, amino acids L95 formed the \(\pi\)-Alkyl interaction force with substrate FPP. Amino acids K238, R321, and R184 formed the \(\pi\)-Anion interaction force with substrate FPP. The remaining 12 amino acids interacted with FPP at the end of the active site cavity by van der Waals force. In addition, 14 amino acids had a mutual force with GPP (Figure 3C). Amino acids K57, S53, L95, and S98 with substrate GPP formed stable hydrogen bonds. The Lys at 57 site, Ser at 53 site, and Leu at 95 formed hydrogen bonds with oxygen atoms of GPP phosphate group, the Ser at 98 site formed hydrogen bonds with hydrogen atoms of GPP phosphate group. Besides, amino acids K57, K238, and R321 formed the \(\pi\)-Alkyl interaction force with substrate GPP. Amino acids K57 formed the \(\pi\)-Anion interaction force with substrate GPP. The remaining eight amino acids interacted with GPP at the end of the active site cavity by van der Waals force.  
In this study, we also chose FPP and GPP as ligands to dock with the remaining seven SmMTPSLs (-5, -15, -23, -33, -37, -46, and -47), respectively. The docking generated the corresponding two-dimensional plan (Figures S2-S8). The docking results showed that each SmMTPSL synthase could successfully connect with the FPP or GPP, which was consistent with the facts that all eight SmMTPSLs can produce terpenoids using FPP or GPP as the substrates.  
Figure 2: Phylogenetic tree of terpen synthase (TPSs) sequences. Sequences included are MTPSLs from _S. moellendorffii_ (orange), ferns (green), red algae (pink), hornworts (gray), and liverworts (blue), and TPSs from fungi (purple) and bacteria (yellow). The tree was constructed with the maximum likelihood method and 1000 replications for bootstrapping. Bootstrap values are not drawn on any nodes with a value less than 70%. A list of genes GenBank accession numbers are given in Table S2.