## 4 Materials and Methods
### RNA Extraction and Transcriptome Analysis
#### 4.3.3 Sequence Analysis, Gene Expression in Yeast, and Product Analysis by GC-MS  
The target gene (SQS-2) was screened from the transcriptome database, and the full-length primers were designed using Primer Premier 5.0 (the primers are shown in Table S4, Dn-SQS-2-F/R). The primers were sent to GENEWIZ Biotechnology Co., Ltd. (South Plainfield, NJ, USA) for synthesis. The total RNA from the leaves of _D. mobile_ was extracted using the CTAB method [61], and the purity and concentration were then measured. Then, the RNA was reverse-transcribed into cDNA using the Thermo Scientific RevertAid First Strand cDNA Synthesis Kit (Thermo Fisher, Waltham, MA, USA) and the full-length gene was cloned using full-length primers. The target gene was connected to the T vector and sent to GENEWIZ Biotechnology Co., Ltd. for sequencing. The accession no. OR059440 was obtained after submitting the sequence to the NCBI database. Sequence alignment was performed using BLAST in DNAman and NCBI, and the integrity of the sequence was checked by the ORF finder. Subsequently, the correctly sequenced gene sequence was cloned into the pESC-TRP expression vector (the primers are shown in Table S4, TRP-SQS-2-F/R) to construct the recombinant plasmid. The recombinant plasmid was introduced into _saccharomyces cerevisiae_ (WAT11) by the lithium acetate method. Then, galactose was added to induce expression, and the extraction liquid was extracted by ethyl acetate after ultrasonic fragmentation. The extraction liquid was dried by a rotary evaporator and then redissolved with 1 mL ethyl acetate. The supernatant was filtered through a 0.22 \(\upmu\)m filter and injected into the GC-MS (7890B-5977A; Agilent Technologies, Palo Alto, CA, USA). The test conditions were as follows: manual injection (1 mL), loading on the Agilent J&W HP-5 ms column, and elution with N\({}_{2}\) at 1.0 mL/min. The temperature of the column box was first maintained at 60 \({}^{\circ}\)C for 1 min, and then increased to 230 \({}^{\circ}\)C at a speed of 10 \({}^{\circ}\)C/min, and finally maintained at this temperature for 30 min. The injector and transmission line temperatures were set at 250 \({}^{\circ}\)C and 270 \({}^{\circ}\)C, respectively. The compounds detected by GC-MS were analyzed using the NIST11 database. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/molecules28237892/s1](https://www.mdpi.com/article/10.3390/molecules28237892/s1)]([https://www.mdpi.com/article/10.3390/molecules28237892/s1](https://www.mdpi.com/article/10.3390/molecules28237892/s1)). Figure S1. Content of dendrobin under different concentrations. Figure S2. Sample quality spectrum analysis total ion current diagram. Figure S3. Differential metabolites analysis. Figure S4. Metabolomics profiling of CK_vs_DF7 group. Figure S5. K-means analysis of differentially expressed genes (DEGs). Figure S6. qRT-PCR analysis of 20 differential genes. Figure S7. Reaction catalyzed by (+)- and (\(-\))-germacene D synthase. Figure S8. Combined transcriptome and metabolome analysis DEGs were significantly correlated with DAMs. Figure S9. Gene cloning, double enzyme digestion of recombinant plasmid agarose gel electrophoresis. Table S1. GO significant enrichment analysis. Table S2. Expression profiles of 238 TFs were corrected with those of structual genes in sesquiterpenoid and triterpenoid biosynthesis. Table S3. Expression profiles of 313 TFs were corrected with those of structual genes in polysaccharides biosynthesis. Table S4. The primers of the twenty selected unigenes. Table S5. Pearson correlation coefficient of DEGs. Table S6. DEGs and DAMs were enriched in the same metabolic pathway and biosynthesis of secondary metabolites pathway. **Author Contributions:** [PERSON] conceived and designed the study, performed experimental measurements, processed and interpreted experimental data, and drafted and revised the manuscript. [PERSON] participated in the design and provided experimental platforms. [PERSON].