## 2 Results
### Spatial and Developmental Expression Patterns of Rice Trans-Prenyltransferases Genes  
To profile the expression patterns of rice _trans_-PT genes, transcript levels were examined by qRT-PCR using rice RNAs from the leaves, roots and florets at stages of seedling, early and late vegetative, reproductive and mature seeds (Figure 4). The _OsGPS_ gene showed relatively low expression, with the highest peak in leaves at reproductive stage. The expression patterns of _OsGGPS1_ and _OsGRP_ genes were very similar, displaying the highest levels in leaves at the early vegetative stage. This expression pattern revealed leaf-preferential expression of three rice PTs of Group I (Figure 4A), reflecting the property to form a heteromeric complex between _OsGGPS1_ and _OsGRP_[10]. Among four rice PTs of Group II, _OsPS1_ and _OsGPS4_ in a subgroup B were expressed at significantly low levels in all tissues. The highest peak of _OsPS4_ in roots was at the early vegetative stage and _OsPS2_ and _OsPS3_ in subgroup A were expressed mainly in leaves of all developmental stages, with the highest peaks at the late vegetative stage (Figure 4B), showing similar expression patterns within the same subgroup. Moreover, the highest expression peak of _OsPS2_ in leaves proposes that an OsPS2 might play a major role as an SPS in the leaves of rice plants. Among five rice PTs of Group III, _OsFPS1_ and \(3\) in subgroup B were expressed with preference to leaves at all developmental stages, while _OsFPS2_, another gene in subgroup B, was mainly expressed in roots of all developmental stages. They were all slightly expressed in florets and seeds. Unlike these, _OsFPS4_ of subgroup A was exclusively expressed in leaves of all developmental stages (Figure 4C). Lastly, the expression of _OsFPS5_ was also analyzed, but was not detected in our data set at all and further investigated in a RiceXPro database to find out that it is quite limitedly expressed in the early stage of embryo (Supplementary Figure S2). Figure 4: Spatial and temporal expression of rice _trans_-PT genes. The endogenous transcript levels of rice _trans_-PT genes in Group I (**A**), Group II (**B**) and Group III (**C**) were examined by qRT-PCR using total RNA isolated from various tissues, including leaves (L) and roots (R) of seedling stage (SS), vegetative stage (VS) and reproductive stage (RS) tissues and florets (F) of RS and seeds (Se) harvested at 40 days after flowering, using gene-specific primers as shown in Table S1. All transcript levels were measured in three technical replicates and were calculated by the \(\Delta\)Ct equation against the _OsUbi5_ gene. The results are expressed as the mean \(\pm\) standard error (SE) and the values are listed in Table S6. Expression Patterns of Rice Trans-Prenyltransferases According to the Treatment of Major Hormones, meJA, GA and ABA  
Since the production of terpene metabolites have been reported to be closely related to responses against various plant hormones, such as methyl jasmonate (meJA) [31; 32], gibberell acid (GA) [33] and abscisic acid (ABA) [34], the transcriptional response of rice _trans_-PTs to meJA, GA and ABA treatments was investigated. The hormone-treated rice whole plants were examined by qRT-PCR with three inducible marker genes; rice terpene synthase 19 (_OsTPS19_, [PERSON] et al. [35]) for meJA, rice gibberell 2-oxidase 3 (_OsGA2 ox3_, [PERSON] et al. [36]) for GA and rice phytoene synthase 1 (_OsPSY1_, [PERSON] et al. [37]) for ABA (Figure 5). After meJA treatment, the expression of _OsGPS_, _OsGGPS1_, _OsSPS1_ and _OsFPS1_ and 3 were remarkably induced and that of _OsGRP_, _OsSPS2_ to 4, and _OsFPS2_ and 4 were suppressed. After GA treatment, the expression of _OsGGPS1_, _OsGRP_, _OsSPS1_, _OsFPS1_ and _OsFPS4_ were induced within 30 min and that of _OsGPS_, _OsSPS2_ to 4 and _OsFPS3_ were increasingly suppressed over time. Post ABA treatment, the expression of _OsGGPS1_, _OsSPS2_ and _OsFPS3_ and 4 were induced beginning at 2 h and the transcript levels of _OsGPS_, _OsGRP_ and _OsFPS2_ were quite reduced.