Identification and Functional Characterization of Tissue-Specific Terpene Synthases in <i>Stevia rebaudiana</i>

• Main Authors: Savitha Dhandapani, Mi Jung Kim, Hui Jun Chin, Sing Hui Leong, In-Cheol Jang
• Format: Article
• Language: English
• Published: MDPI AG 2020-11-01
• Series: International Journal of Molecular Sciences
• Subjects: stevia; <i>Stevia rebaudiana</i>; terpenoids; terpene synthase; volatile organic compounds
• Online Access: https://www.mdpi.com/1422-0067/21/22/8566
• ISSN: 1661-6596; 1422-0067

In addition to the well-known diterpenoid steviol glycosides, <i>Stevia rebaudiana</i> (Stevia) produces many labdane-type diterpenoids and a wide range of mono- and sesquiterpenoids. However, biosynthesis of mono- and sesquiterpenoids in Stevia remains unknown. Here we analyzed the extracts of Stevia leaves, flowers, stems, and roots by Gas Chromatography–Mass Spectrometry and putatively identified a total of 69 volatile organic compounds, most of which were terpenoids with considerably varied quantities among the four tissues of Stevia. Using Stevia transcriptomes, we identified and functionally characterized five terpene synthases (TPSs) that produced major mono- and sesquiterpenoids in Stevia. Transcript levels of these Stevia <i>TPS</i>s and levels of corresponding terpenoids correlated well in Stevia tissues. Particularly, the root-specific SrTPS4 and SrTPS5 catalyzed the formation of γ-curcumene/zingiberene/β-sesquiphellandrene and α-longipinene/β-himachalene/himachalol as multifunctional sesqui-TPSs, respectively. Most of the <i>SrTPSs</i> were highly responsive to various environmental stresses in a tissue-specific manner. Taken together, our results provide new insights into how Stevia produces diverse terpenoids to confer differential responses to various environmental factors in each tissue.