Functional Characterization of BGlu12, a β-Glucosidase from , Provides Insights into Its Role in Abiotic Stress through Accumulation of Antioxidant Flavonols.

Glycosylation and deglycosylation are impressive mechanisms that allow plants to regulate the biological activity of an array of secondary metabolites. Although glycosylation improves solubility and renders the metabolites suitable for transport and sequestration, deglycosylation activates them to carry out biological functions. Herein, we report the functional characterization of BGlu12, a β-glucosidase from BGlu12 has a characteristic glucoside hydrolase 1 family (α/β) triose-phosphate isomerase (TIM) barrel structure with a highly conserved active site. enzyme activity revealed that BGlu12 catalyzes the hydrolysis of flavonol β-glucosides and cello-oligosaccharides. Site-directed mutagenesis of any of the two conserved catalytic glutamic acid residues (Glu and Glu) of the active site completely abolishes the β-glucosidase activity. Transcript analysis revealed that is highly induced in response to UV-B, dehydration, NaCl, methyl jasmonate, and abscisic acid treatments indicating its possible role in plant stress response. Transient overexpression of BGlu12 leads to the accumulation of antioxidant flavonols in and confers tolerance to abiotic stresses. Antioxidant assays indicated that accumulation of flavonols alleviated the accretion of reactive oxygen species during abiotic stress conditions. β-Glucosidases are known to play a role in abiotic stresses, particularly dehydration through abscisic acid; however, their role through accumulation of reactive oxygen species (ROS) scavenging flavonols has not been established. Furthermore, only one β-glucosidase 12 homolog has been characterized so far. Therefore, this work presents an important report on characterization of BGlu12 and its role in abiotic stress through ROS scavenging.