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Updated: Jan 23, 2026

Flavonoid Content During the Growth and Floral Development of Calendula officinalis L.
Published on: June 27, 2025
Functional characterization of a flavonoid and triterpene glycosyltransferase, GgUGT73B34, conferring ABA-independent
Bhawna Verma1, Shahnawaz Hussain1, Ritu Devi1
1Plant Sciences and Agro-technology Division, India; CSIR-Indian Institute of Integrative Medicine, Canal Road, Jammu, (Jammu and Kashmir)-180001, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, 201002, India.
Abstract:
Drought stress poses a major challenge to global crop yields, necessitating the identification of drought-responsive genes essential for improving plant tolerance and productivity under water deficit conditions. UDP-glycosyltransferases are key enzymes that modulate plant metabolism through glycosylation, playing a critical role in coping with environmental stresses. In this study, we functionally characterized a flavonoid/triterpene glucosyltransferase gene, UGT73B34, from Glycyrrhiza glabra, induced by osmotic stress. Transgenic Nicotiana tabacum plants overexpressing GgUGT73B34 exhibited significantly enhanced growth and survival under drought mediated through an ABA-independent mechanism. The OE-6 line of GgUGT73B34 plants exhibited superior water retention, reduced stomatal apertures, low reactive oxygen species and decreased transpiration rates compared to wild-type controls. These physiological advantages correlated with elevated accumulation of flavonoids, phenolics, proline, soluble sugars, and indole-3-acetic acid. Gene expression analysis revealed downregulation of ABA-dependent drought-responsive genes (ABI4, ABI5, ERD10a) and antioxidant enzymes (APX, GST, CAT2, PRX), while strongly inducing ABA-independent regulators DREB3 and SnRK2.1, indicating a strategic shift toward sustained drought resilience. Homology-model based structure analysis revealed a conserved GT-B fold with flexible substrate-binding domains, enabling broad specificity for diverse metabolites interacting predominantly with His and Glu as key amino acid residues. In vitro enzymatic assays confirmed mono- and di-glycosylation of glabridin, liquiritigenin, licochalcone A, and 18α-glycyrrhetinic acid as validated by LC-MS/MS analysis. Our findings demonstrated that GgUGT73B34 confers drought tolerance through coordinated regulation of osmoregulation, antioxidant capacity, and hormone homeostasis via an ABA-independent pathway, providing valuable insights for developing drought-resilient crops and for engineering enhanced production of bioactive natural products.
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