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SummaryPlants experience numerous biotic stresses throughout their lifespan, such as pathogens and pests, which can substantially affect crop production. In response, plants have evolved various metabolites that help them withstand these stresses. Here, we show that two specialized metabolites in the herbaceous perennial Belamcanda chinensis, tectorigenin and its glycoside tectoridin, have diverse defensive effects against phytopathogenic microorganisms and antifeeding effects against insect pest. We further functionally characterized a 7‐O‐uridine diphosphate glycosyltransferase Bc7OUGT, which catalyses a novel reversible glycosylation of tectorigenin and tectoridin. To elucidate the catalytic mechanisms of Bc7OUGT, we solved its crystal structure in complex with UDP and UDP/tectorigenin respectively. Structural analysis revealed the Bc7OUGT possesses a narrow but novel substrate‐binding pocket made up by plentiful aromatic residues. Further structure‐guided mutagenesis of these residues increased both glycosylation and deglycosylation activities. The catalytic reversibility of Bc7OUGT was also successfully applied in an one‐pot aglycon exchange reaction. Our findings demonstrated the promising biopesticide activity of tectorigenin and its glycosides, and the characterization and mechanistic study of Bc7OUGT could facilitate the design of novel reversible UGTs to produce valuable glycosides with health benefits for both plants and humans.

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A fluorescence enhancement phenomenon in the europium (Eu)-Ofloxacin (OF)-Sodium Dodecyl Benzene Sulfonate (SDBS) fluorescence system was observed when Gd(3+) was added. The fluorescence intensity of the systems was measured (lambda (ex)/lambda (em) = 280/612 nm) at pH 7.8. Under optimum conditions, a linear relationship between the enhanced fluorescence intensity and the Eu(3+) concentration in the range of 5.0 x 10(-10) approximately 2.0 x 10(-7) mol x L(-1) was observed. The detection limit of Eu(3+) was 1.46 x 10(-10) mol x L(-1) (S/N = 3). This method was used for the determination of trace amounts of europium in synthetic rare earth samples with satisfactory results. In addition, the interaction mechanism is also studied.