Table 1.
Main UGTs described in this review.
| UGT | Substrate | Role in planta | Inducing factor |
|---|---|---|---|
| Flavonoids | |||
| UGT71C1 (Arabidopsis) | Flavonoids, lignans | Flavonoid aglycones are potentially more antioxidant than their glycosylated forms, explaining the better tolerance of knockout mutants to methyl viologen. | Unknown |
| UGT73B1, UGT73B2, UGT73B3 (Arabidopsis) | Flavonoids | Pathogen infection, SA, methyl jasmonate, oxidative stress | |
|
UGT78A14 (Camellia sinensis) |
Kaempferol, quercetin | Kaempferol and quercetin glycosylation products have higher ROS scavenging activity (FRAP, DPPH and ABTS) than their corresponding aglycones and contribute to cold stress tolerance. | Cold stress |
| UGT79B2/UGT79B3 (Arabidopsis) | Cyanidin/cyanidin-3-O-glucoside | Glycosylation of anthocyanins results in their storage in the vacuole, derepressing the product feedback inhibition on PAL and increasing total anthocyanin content. Plants are therefore more tolerant to cold, salt, and drought stresses. | Cold, salt, and drought stresses |
|
UFGT2 (Zea mays) |
Quercetin, kaempferol | Flavonoids can protect the plant from oxidative stress resulting from exposure to salt, H2O2 and high osmotic condition. Glycosylation supports the biosynthesis of these flavonoids. | Salt, drought and oxidative stresses |
| Phytohormones | |||
|
SDG8i (Sporobolus stapfianus) |
Strigolactones | Overexpression of this gene in Arabidopsis results in higher tolerance to salt, freezing and drought stresses. Strigolactones favour the biosynthesis of anthocyanins and strigolactones glycosylation may ease their translocation between different organs. | Water stress |
| UGT71B6, UGT71B7, UGT71B8 (Arabidopsis) | ABA | These UGTs maintain an optimal ABA content under non-limiting growing conditions and may mitigate ABA response during salt and osmotic stress. | ABA, salt and osmotic stresses |
| UGT74E2 (Arabidopsis) | Indole-3-butyric acid | The enzymatic activity of UGT74E2 may modify auxin gradient and distribution to support plant acclimation under drought and salt stress conditions, in interaction with flavonoids. | Osmotic, oxidative, ultraviolet B and salt stresses |
|
UGT90A1 (Oryza sativa) |
Possibly auxins and cytokinins | Overexpression in rice and Arabidopsis leads to higher tolerance to cold and salt stress, with lower accumulation of ROS and higher catalase and soluble PRX activities. | Low temperature, salt stress |
| Miscellaneous | |||
|
TOGT (Nicotiana tabacum) |
Scopoletin | Scopoletin is an antiviral and a potent antioxidant in plant defense response. Scopoletin regulates ROI accumulation in cells surrounding necrosis (as substrate of PRX or direct ROI scavenger). | SA- and pathogen-inducible |
| UGT73B3, UGT73B5 (Arabidopsis) | Phytoprostanes, camalexin degradation products | These UGTs contribute to the regulation of redox status and general detoxification of ROS-reactive specialized metabolites, limitation of cell death establishment during HR. | Early-SA induced gene, paraquat, ozone, bacteria |
|
UGT85A5 (Arabidopsis) |
Unknown | Ectopic expression increases tolerance to salt stress, as indicated by lower loss of chlorophyll and lower malondialdehyde equivalents content. | Salt stress |
|
UGT91Q2 (Camellia sinensis) |
Nerolidol | Nerolidol glucoside has a higher ROS scavenging activity than its aglycone, possibly protects PSII during cold stress and prevents lipid peroxidation. | Cold stress |
ABA, abscisic acid; ABTS, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid); DPPH, 2,2-diphenyl-1-picrylhydrazyl; FRAP, ferric reducing ability of plasma; HR, hypersensitive response; PAL, phenylalanine ammonia lyase; PRX, peroxidase; PSII, photosystem II; ROI, reactive oxygen intermediates; ROS, reactive oxygen species; SA, salicylic acid.
Additional details and corresponding references are provided in the main text.