## 2 Results
### Candidate Genes Involved in Terpenoid Biosynthesis  
To explore the regulatory mechanisms for the accumulation patterns of different terpenoids in C. _porrectum_, the expression profiles of genes involved in terpenoid biosynthesis were analyzed. In the eucalypttD chemotype and linalool chemotype, the camphor chemotype and eucalypttD chemotype, and the camphor chemotype and linalool chemotype comparison groups, 52, 49 and 66 DEGs for the biosynthesis of terpen were identified, respectively (Figure 4, Figure S3 and Figure S4). The expression level of all these unigenes are shown in the Figure 4, Figures S3 and S4, and the fragments per kilobase per million mapped (FPKM) values are shown in Table S3. Most of the genes exhibited a high transcriptome expression level, which encoding key enzymes in the MEP and MVA pathway (KEGG entry ko00900). The expression levels of different unigenes among the three different chemotypes were different, but the unigene expression level of the MEP pathway was higher than that of the MVA pathway as a whole (Figure 4, Figures S3 and S4). Both MEP and MVA pathways produce IPP and its isomer, dmapp. The active biosynthesis of building blocks contributes to the accumulation of various terpenoids, which is consistent with our analysis in the components of the extracts from the leaves of C. _porrectum_ (Table 1). Moreover, in the eucalypttD chemotype and linalool chemotype comparison group, we screened 21 unigenes encoding TPS, namely, 7 monoterpene synthases, 3 diterpenoid synthases and 11 sesquiterpene and triterpene synthases (Figure 4). The eucalypttD chemotype upregulated 5 unigenes of monoterpene synthases, 1 unigene of diterpene synthase and 4 unigenes involving sesquiterpene and triterpene synthases. However, in the linalool chemotype, 2 unigenes of monoterpene synthases, 2 unigenes of diterpene biosynthesis, and 7 unigenes of sesquiterpene and triterpene synthases were upregulated (Figure 4). In the camphor chemotype and eucalypttD chemotype comparison group, we screened 22 unigenes encoding TPS, namely, 9 monoterpene synthases, 3 diterpenoid synthases and 10 sesquiterpene and triterpene synthases (Figure S3). The camphor chemotype upregulated 3 unigenes of monoterpene synthases, 2 unigenes of diterpene synthases and 6 unigenes of sesquiterpene and triterpene synthases. However, in the eucalypttD chemotype, 6 unigenes of monoterpene synthases, 1 unigene of diterpene biosynthesis, and 4 unigenes of sesquiterpene and triterpene synthases were upregulated (Figure S3). In the camphor chemotype and linalool chemotype comparison group, we screened 18 unigenes encoding TPS, namely, 5 monoterpene synthases, 2 diterpenoid synthases and 11 sesquiterpene and triterpene synthases (Figure S4). The camphor chemotype upregulated 2 unigenes of monoterpene synthases, 2 unigenes of diterpene synthase and 5 unigenes of sesquiterpene and triterpene synthases. However, in the linalool chemotype, 3 unigenes of monoterpene synthases and 6 unigenes of sesquiterpene and triterpene synthases were upregulated (Figure S3). In the camphor chemotype and linalool chemotype comparison group, we screened 18 unigenes encoding TPS, namely, 5 monoterpene synthases, 2 diterpenoid synthases and 11 sesquiterpene and triterpene synthases (Figure S4). The camphor chemotype upregulated 2 unigenes of monoterpene synthases, 2 unigenes of diterpene synthase and 5 unigenes of sesquiterpene and triterpene synthases. However, in the linalool chemotype, 3 unigenes of monoterpene synthases and 6 unigenes of sesquiterpene and triterpene synthases were upregulated (Figure S4). On the whole, the observed high expression levels of enzymes in the terpene skeleton pathway were consistent with the high rate of terpenoid synthesis and suggest that the different terpenoid compositions in the three chemotypes may arise from differences in the expression levels of TPS genes.