Volatile Glycosylation in Tea Plants: Sequential Glycosylations for the Biosynthesis of Aroma β-Primeverosides Are Catalyzed by Two Camellia sinensis Glycosyltransferases

Abstract

Tea plants (Camellia sinensis) store volatile organic compounds (VOCs; monoterpene, aromatic, and aliphatic alcohols) in the leaves in the form of water-soluble diglycosides, primarily as b-primeverosides (6-O-b-D-xylopyranosyl-b-D-glucopyranosides). These VOCs play a critical role in plant defenses and tea aroma quality, yet little is known about their biosynthesis and physiological roles in planta. Here, we identified two UDP-glycosyltransferases (UGTs) from C. sinensis, UGT85K11 (CsGT1) and UGT94P1 (CsGT2), converting VOCs into b-primeverosides by sequential glucosylation and xylosylation, respectively. CsGT1 exhibits a broad substrate specificity toward monoterpene, aromatic, and aliphatic alcohols to produce the respective glucosides. On the other hand, CsGT2 specifically catalyzes the xylosylation of the 69-hydroxy group of the sugar moiety of geranyl b-D-glucopyranoside, producing geranyl b-primeveroside. Homology modeling, followed by site-directed mutagenesis of CsGT2, identified a unique isoleucine-141 residue playing a crucial role in sugar donor specificity toward UDP-xylose. The transcripts of both CsGTs were mainly expressed in young leaves, along with b-PRIMEVEROSIDASE encoding a diglycoside-specific glycosidase. In conclusion, our findings reveal the mechanism of aroma b-primeveroside biosynthesis in C. sinensis. This information can be used to preserve tea aroma better during the manufacturing process and to investigate the mechanism of plant chemical defenses.

Glucosylation of (Z)‐3‐hexenol informs intraspecies interactions in plants: A case study in Camellia sinensis

“…The catalytic efficiency of CsUGT85A53‐1 for (Z)‐3‐hexenol ( k cat / K M of 18,499 M −1 s −1 ) is 1.2‐ and 2‐fold higher than that of CsUGT85A53‐2 and CsUGT85A53‐3, respectively (Table ). The kinetics of UGT85K11 for (Z)‐3‐hexenol was further studied (Ohgami et al, ). The apparent K M values of UGT85K11 for (Z)‐3‐hexenol was 40.66 μM (Table S6), which was 2.1‐, 1.5‐, and 1.6‐fold higher than that of CsUGT85A53‐1, CsUGT85A53‐2, and CsUGT85A53‐3 (Table ).…”

“…In terms of the biosynthesis of flavour glycosides, genes for some UGTs have been isolated and identified, recently. Although the phylogenetic analysis can provide information that is able to partially predict the biochemical activities of plant UGTs, some of the enzymes, which were classified in the same cluster, can exhibited different functionalities (Figure ; Ono et al, ; Yauk et al, ; Ohgami et al, ; Song, Hong, et al, ). In our study, the UGT85 family member CsUGT85A53 preferentially glucosylated (Z)‐3‐hexenol, nerol, and other aromatic alcohols (Figure ), whereas AdGT4 from Actinidia deliciosa (Yauk et al, ) and VvGT14 from Vitis vinifera (Bönisch et al, ) showed a similar broad substrate tolerance but with a preference for geraniol.…”

“…UGT85K11 from C . sinensis was recently reported to catalyse the formation of geranyl glucoside, but also accepted (Z)‐3‐hexenol and produced (Z)‐3‐hexenyl glucoside to some extent (62% of the activity with geraniol; Ohgami et al, ). The enzymatic activity of CsUGT85A53‐1 and UGT85K11 towards (Z)‐3‐hexenol were further compared in the current study.…”

Identification of a Flavonoid Glucosyltransferase Involved in 7-OH Site Glycosylation in Tea plants (Camellia sinensis)

“…This evidence has been derived from the elucidation of crystal structure, and site-directed mutagenesis studies 15, 43–45 .…”

Glucosylation of 4-Hydroxy-2,5-Dimethyl-3(2H)-Furanone, the Key Strawberry Flavor Compound in Strawberry Fruit

“…Knowledge of the underlying catalytic and regulatory mechanisms and their physiological roles would be of great biotechnological importance for the synthesis of bioactive secondary metabolites in vitro and for the metabolic engineering of crops with important agronomic traits through efficient breeding strategies Kristensen et al, 2005;Weis et al, 2008). Although the ubiquitous GT family has been intensively studied for many years (Gachon et al, 2005) and enzymes involved in the glucosylation of plant products such as anthocyanidins, flavonoids, terpenes, alcohols (Cheng et al, 1994;Almeida et al, 2007;Griesser et al, 2008aGriesser et al, , 2008bBönisch et al, 2014aBönisch et al, , 2014bOhgami et al, 2015), and plant hormones have been functionally characterized, little is actually known about the glucosylation of strawberry aroma chemicals.…”