초록
<P><B>SUMMARY</B></P><P>Identification of unknown metabolites and their biosynthetic genes is an active research area in plant specialized metabolism. By following a gene–metabolite association from a genome‐wide association study of Arabidopsis stem metabolites, we report a previously unknown metabolite, 2‐hydroxy‐2‐(1‐hydroxyethyl)pentanoic acid glucoside, and demonstrated that UGT76F1 is responsible for its production in Arabidopsis. The chemical structure of the glucoside was determined by a series of analyses, including tandem MS, acid and base hydrolysis, and NMR spectrometry. T‐DNA knockout mutants of UGT76F1 are devoid of the glucoside but accumulate increased levels of the aglycone. 2‐hydroxy‐2‐(1‐hydroxyethyl)pentanoic acid is structurally related to the C7‐necic acid component of lycopsamine‐type pyrrolizidine alkaloids such as trachelantic acid and viridifloric acid. Feeding norvaline greatly enhances the accumulation of 2‐hydroxy‐2‐(1‐hydroxyethyl)pentanoic acid glucoside in wild‐type but not the UGT76F1 knockout mutant plants, providing evidence for an orthologous C7‐necic acid biosynthetic pathway in Arabidopsis despite the apparent lack of pyrrolizidine alkaloids.</P><P><B>Significance Statement</B></P><P>The present study reports a previously unknown metabolite and the function of UGT76F1 in Arabidopsis. This metabolite is structurally related to the C7‐necic acid moiety of certain pyrrolizidine alkaloids, suggesting that necic acid biosynthesis may have a wider taxonomic distribution in non‐alkaloid‐containing species.</P>