## 5 Conclusions  
Our investigation into finger citron metabolite and transcriptome provides new insights into the biosynthesis of terpenoids. In finger citron, expression of upstream genes in the MVA and MEP pathways did not change much during organ development. Terpenoid diversity was caused by differential TPS expression. Based on PLS models, we identified 6 volatiles differentially accumulated in different finger citron organs. Together with the two volatiles with highest contents, these can be considered as the characteristic components of finger citron and can be used to distinguish finger citron from other _Citrus_ species. Our results showed there are 58 members of the finger citron _TPS_ gene family. The expression patterns of six TF families with 901 members in finger citron organs were also explored. Finally, we obtained 45 gene modules from WGCNA. Based on the high-connectivity subnetwork of Module Red and Module Green, 13 _TPS_s were suggested to play important roles in finger citron characteristic aroma. In addition, 15 TFs were identified whose locations in the subnetwork implied they function in regulating terpenoid metabolism. Future work should focus on the direct and indirect interaction among these target genes and regulators to elucidate the functioning network that controls terpene production.  
**Supplementary Materials:** The following are available online. Table S1: Content (ug/g FW) of 62 identified volatiles in finger citron; Table S2: Summary of the Finger Citron Transcriptome; Table S3: Summary of TF family gene ID. Table S4: Gene ID and annotations in Module Red. Table S5: Gene ID and annotations in Module Green. Table S6: Primer pairs used in qRT-PCR validation. Table S7: The expression profile of assembled genes in RNA-Seq. Figure S1: Results of permutation tests for PLS-DA using volatiles as variables; Figure S2: Pearson correlations between tested samples based on RNA-Seq data; Figure S3: Expression levels of genes based on RNA-Seq data; Figure S4: Schematic diagram of finger citron _TPS_ gene structure. Figure S5: Expression analysis of finger citron TPS genes using RNA-Seq and RT-qPCR. Figure S6: Hierarchical clustering and heat map visualization of changes in transcription factor expression level in developing organs of finger citron; Figure S7:Module Red and Module green coexpression networks; Figure S8: Gene co-expression subnetwork of Module Blue and gene annotations; Figure S9: Amino acid sequence similarity of finger citron TPSs and functional characterized TPSs from other _Citrus_ species.  
**Author Contributions:** [PERSON], [PERSON] and K.C. conceived and designed the experiments; [PERSON] and [PERSON] performed the experiments in the laboratory; [PERSON], provided the materials; [PERSON], [PERSON], and [PERSON] analyzed the data, and wrote the article; [PERSON], [PERSON], and K.C. revised the manuscript. All authors read and approved the final article.  
**Funding:** This research was supported by National Key R&D Program of China (2016 YFD0400101), Zhejiang Provincial Science and Technology Project (2016C04001), Key Project for New Agricultural Cultivar Breeding in Zhejiang Province (2016C02052-1) and Fundamental Research Funds for the Central Universities (2019 FZA6010).  
**Acknowledgments:** We thank [PERSON] for helping PLS-DA analysis and VID-coefficient calculating.  
**Conflicts of Interest:** The authors declare no conflict of interest.