Glycosyltransferase UGT79B7 negatively regulates hypoxia response through γ-aminobutyric acid homeostasis in Arabidopsis

Hypoxia induced by flooding or submergence is a serious abiotic stress affecting crop productivity worldwide. Through evolution, plants have developed different metabolic mechanisms to cope with ATP deficiency caused by hypoxia. Among these, the metabolism of gamma-aminobutyric acid (GABA), a non-protein amino acid, is recognized as a crucial component of low-oxygen stress responses because of its link in both carbon and nitrogen metabolism. However, it is largely unknown how GABA homeostasis is controlled. In this study, we identified a novel glycosyltransferase encoding gene, UGT79B7, which was significantly down-regulated under low-oxygen in Arabidopsis. ugt7967 knockout mutants showed increased resistance to hypoxia, while the overexpression lines showed increased sensitivity. We demonstrated that glycosyltransferase UGT79B7 could catalyse GABA to form GABA glucose conjugate (GABA-Glc) in vitro, and control GABA glycosylation in vivo. Moreover, UGT79B7 negatively modulated the accumulation of GABA under hypoxia. Our data suggest that the glycosylation of GABA plays an important role in GABA homeostasis and reveal a new mechanism of regulation of the hypoxia response through a dynamic balance of GABA and its glycosylation product, GABA-Gic.

Automated summary

Plants have developed metabolic mechanisms to cope with ATP deficiency caused by hypoxia, including the glycosylation of GABA catalyzed by glycosyltransferase UGT79B7. This process controls the accumulation of GABA in response to hypoxia, revealing a new mechanism of regulation for the hypoxia response.