## 2 Results  
### Phylogenetic Tree Analysis of Rice Trans-Prenyltransferases  
Twelve genes of rice _trans_-PTs were identified from the rice whole genome database, through the BLAST (Basic Local Alignment Search Tool) search engine. To more precisely predict their function, we performed further informatics searches of molecular databases and constructed an extended phylogenetic tree with 136 plant PTs collected from 13 monocot plant species, including rice, corn, wheat, barley, sorghum and 39 dicot plants including major crops (Figure 1, Supplementary Table S3). Three groups of Group I (GPS/GGPS/GFPS family), II (SPS/PPS family) and III (FPS family) were classified to be further assorted into six (A to F), two (A and B) and three (A to C) subgroups, respectively (Figure 1). Among them, twelve of the rice PTs were classified, with three in Group I, four in Group II and five in Group III and their gene information was summarized with some corrections (Table 1). Figure 1: Evolutionary relationships among plant _trans_-PTs family. The deduced amino acid sequences of 136 plant _trans_-PTs genes were aligned using BioEdit 7.2.5 software with ClustalW algorithm and the phylogenetic tree was generated using MEGA 7.0.26 software by Maximum Likelihood tree method based on the ClustalW alignment. The scale bar represents the branch length at 0.50 substitutions per site. Plant PTs are named by the combination of a species abbreviation and an accession number and rice PTs are marked in red letters. All information of plant _trans_-PTs used in phylogenetic analysis is listed in Table S3. First in Group I, OsGGPS1 was classified as GGPS_LSU (subgroup A) along with several uncharacterized monocot and dicot PTs, separately from most known GGPS homologs of hop (HI ACQ90682), _Arabidopsis_ (AtGGPS11, AT4G36810) and peppermint (Mp AAF08793). These known GGPS homologs were classified as GGPS_LSU (subgroup A), which has functions as homomeric GGPS or heteromeric GPS when formed in a complex with GGPS_SSUs [11; 23]. Additionally, five _Arabidopsis_-specific GGPSs were classified as GFPS (subgroup B) between two LSU subgroups, adding further support for the previous suggestion that they evolved from GGPS_LSU to biosynthesize the longer product of GFPP (C\({}_{25}\)) [13]. Secondly, OsGPS was classified as G(G)PS (subgroup C) with two monocot PTs from corn (_Zea may_, ABQ85648) and sorghum (_Sorghum bicolor_, XP_021311468), but separately from the well-characterized homomeric GPS (subgroup D) originating from Grand fir (_Abies grandis_, AAN01134, [PERSON] [25]) and Norway spruce (_Picea abies_, ACA21458, [PERSON] and Gershenzon [26]). A G(G)PS (subgroup C) included four AtGGPSs (AtGGPS1, 3, 4 and 8) that have GGPS/PPS activities mainly when using FPPs as allylic substrates [13], supposing that monocot PTs of subgroup C containing OsGPS might be a type of PT family commonly using FPPs as allylic substrates. The third rice PT, OsGRP, was classified with other uncharacterized monocot PTs in GGPS_SSU-II (subgroup F) containing AtGGPS12 (At4G38460, [PERSON] et al. [27]), but separately from GGPS_SSU-I (subgroup E) including the heterodimeric GPS of hop (HI ACQ90681) and the heterotetrameric GPS of peppermint (Mp AAF08792) that form a complex with hop (HI ACQ90682) or peppermint (Mp AAF08793) in GGPS_LSU subgroup as counterparts [11; 23]. Collectively in Group I, the GPS/GGPS/GFPS family have evolved to have six subgroups of A-F in the plant kingdom, resulting in offering different preferences of enzymatic activities for the production of isoprenyl-PPs. Rice has evolved to have a limited number of GPS/GGPS/GFPS genes as there are only three, in contrast to the existence of twelve GPS/GGPS/GFPS genes in _Arabidopsis_. Next for Group II, as the SPS/PPS family, four rice PTs were identified in the whole genome, including the already known OsPS1 and 2 [20] and OsSPS3 [21] and the new OsSPS4 in this study (Figure 1 and Table 1).