Qualitative and Quantitative NAD+ Metabolomics Lead to Discovery of Multiple Functional Nicotinate N-Glycosyltransferase in Arabidopsis

Lingyun Liu; Fengxia Zhang; Guosheng Li; Guodong Wang

doi:10.3389/fpls.2019.01164

Qualitative and Quantitative NAD⁺ Metabolomics Lead to Discovery of Multiple Functional Nicotinate N-Glycosyltransferase in Arabidopsis

Front Plant Sci. 2019 Sep 27:10:1164. doi: 10.3389/fpls.2019.01164. eCollection 2019.

Authors

Lingyun Liu^{1

2}, Fengxia Zhang¹, Guosheng Li^{1

2}, Guodong Wang^{1

2}

Affiliations

¹ State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, China.
² College of Advanced Agricultural Sciences, University of the Chinese Academy of Sciences, Beijing, China.

Abstract

The Preiss-Handler pathway, which salvages nicotinate (NA) for NAD synthesis, is a conserved biochemical pathway in land plants. We previously demonstrated that various NA conjugations (mainly methylation and glycosylation) shared the NA detoxification function in all tested plants. It remains unclear whether other NA conjugates with low abundance exist in plants. In this study, we discovered at least two additional NA N-glycosides in Arabidopsis, which was tentatively elucidated as nicotinate N-pentoside (NaNP) and NA N-rhamoside (NaNRha), using liquid chromatography triple-quadrupole mass spectrometry (LC-QQQ-MS) with precursor ion-scanning (PreIS). We further quantitatively profile the NAD⁺-related metabolites in 24 tissues of Arabidopsis. Biochemical assays of UGT76C family revealed that UGT76C5 (encoded by At5g05890, previously identified as NaNGT) was a multiple functional nicotinate N-glycosyltransferase, with high preference to UDP-xylose and UDP-arabinose. The deficiency of NaNP and NaNRha in ugt76c5 mutant suggested that UGT76C5 is responsible for biosynthesis of NaNP and NaNRha in planta. We also identify one amino acid difference in PSPG (plant secondary product glycosyltransferase) motif is responsible for the divergence of NaNGT (UGT76C4) and UGT76C5. Taken together, our study not only identifies a novel nicotinate N-glycosyltransferase but also paves the way for investigations of the in planta physiological functions of various NA conjugations.

Keywords: Arabidopsis; N-glycosyltransferase; NAD; Preiss-Handler pathway; nicotinate.