Attractive but Toxic: Emerging Roles of Glycosidically Bound Volatiles and Glycosyltransferases Involved in Their Formation

Abstract

Plants emit an overabundance of volatile compounds, which act in their producers either as appreciated attractants to lure beneficial animals or as repellent toxins to deter pests in a species-specific and concentration-dependent manner. Plants have evolved solutions to provide sufficient volatiles without poisoning themselves. Uridine-diphosphate sugar-dependent glycosyltransferases (UGTs) acting on volatiles is one important part of this sophisticated system, which balances the levels of bioactive metabolites and prepares them for cellular and long-distance transport and storage but enables the remobilization of disarmed toxins for the benefit of plant protection. This review provides an overview of the research history of glycosidically bound volatiles (GBVs), a relatively new group of plant secondary metabolites, and discusses the role of UGTs in the production of GBVs for plant protection.

Glucosylation of the phytoalexin N‐feruloyl tyramine modulates the levels of pathogen‐responsive metabolites in Nicotiana benthamiana

“…Similarly, UGT85 enzymes and UGT709Q1 (inactive) formed a separate group in the phylogenetic tree (Figure S4) supporting the functional difference. As considerable transcript levels of UGT85A73 were found in tobacco flower and the encoded protein preferentially glucosylated nonpolar, low‐molecular‐weight compounds, we proposed that this enzyme is implicated in the modification of tobacco flower volatiles (Song et al ., ). UGT85s from tea plant, grape, and kiwifruit were shown to catalyze the glucosylation of volatiles, including geraniol, citronellol, hexanol, (Z)‐3‐hexenol, octanol, 2‐phenylethanol, benzyl alcohol, and 2,5‐dimethyl‐4‐hydroxy‐3(2H)‐furanone (furaneol; Bönisch et al ., ; Song et al ., ; Jing et al ., ).…”

“…As considerable transcript levels of UGT85A73 were found in tobacco flower and the encoded protein preferentially glucosylated nonpolar, low‐molecular‐weight compounds, we proposed that this enzyme is implicated in the modification of tobacco flower volatiles (Song et al ., ). UGT85s from tea plant, grape, and kiwifruit were shown to catalyze the glucosylation of volatiles, including geraniol, citronellol, hexanol, (Z)‐3‐hexenol, octanol, 2‐phenylethanol, benzyl alcohol, and 2,5‐dimethyl‐4‐hydroxy‐3(2H)‐furanone (furaneol; Bönisch et al ., ; Song et al ., ; Jing et al ., ). Biochemical analyses of the recombinant UGT709C2 protein showed that it possessed catalytic efficiency towards 7‐deoxyloganetate, a precursor of the loganin and secologanin pathway (Asada et al ., ).…”

Sesquiterpene glucosylation mediated by glucosyltransferase UGT91Q2 is involved in the modulation of cold stress tolerance in tea plants

“…Recent studies have shown that UGTs also play an important role in plant growth and development and in response to biological and abiotic stresses (Tiwari et al , ; Rehman et al , ). To date, only a few volatiles and their corresponding UGTs have been functionally characterized due to the presence of hundreds of UGT‐encoding genes in most plant species (Yonekura‐Sakakibara & Hanada ; Caputi et al ; Song et al ) and substrate promiscuity of UGT enzymes (Jones & Vogt, ). In contrast to the intensively studied UGTs involved in the glucosylation of monoterpenols (Bönisch et al , ,b; Yoneya & Takabayashi, ; Ohgami et al , ) and nonvolatile diterpenoids (C20) (Richman et al , ; Nagatoshi et al , ; Sun et al , ), the UGTs involved in the glucosylation of sesquiterpenes have been scarcely documented, possibly due to the relative rarity of sesquiterpene glycosides in the plant kingdom.…”

Natural variations in the MYB transcription factor MYB31 determine the evolution of extremely pungent peppers

“…Plants have evolved numerous specialized metabolites that play essential roles in mediating interactions between plants and their habitats (Song et al ., ), and these compounds constitute a valuable resource for the discovery of economically important bioactive structures (Mithöfer & Boland, ; Shang et al ., ; Kajikawa et al ., ). Intriguingly, some plants have evolved fruit‐specific defensive chemicals to deter herbivores and prevent their fruits and seeds from being attacked by microbes (Tewksbury et al ., , ).…”