OsEIL1 protects rice growth under NH 4 + nutrition by regulating OsVTC1-3-dependent N-glycosylation and root NH 4 + efflux.

Rice is known for its superior adaptation to ammonium (NH 4 + ) as a nitrogen source. Compared to many other cereals, it displays lower NH 4 + efflux in roots and higher nitrogen-use efficiency on NH 4 + . A critical role for GDP-mannose pyrophosphorylase (VTC1) in controlling root NH 4 + fluxes was previously documented in Arabidopsis, but the molecular pathways involved in regulating VTC1-dependent NH 4 + efflux remain unclear. Here, we report that ETHYLENE-INSENSITIVE3-LIKE1 (OsEIL1) acts as a key transcription factor regulating OsVTC1-3-dependent NH 4 + efflux and protein N-glycosylation in rice grown under NH 4 + nutrition. We show that OsEIL1 in rice plays a contrasting role to Arabidopsis-homologous ETHYLENE-INSENSITIVE3 (AtEIN3) and maintains rice growth under NH 4 + by stabilizing protein N-glycosylation and reducing root NH 4 + efflux. OsEIL1 constrains NH 4 + efflux by activation of OsVTC1-3, but not OsVTC1-1 or OsVTC1-8. OsEIL1 binds directly to the promoter EIN3-binding site (EBS) of OsVTC1-3 in vitro and in vivo and acts to increase the transcription of OsVTC1-3. Our work demonstrates an important link between excessive root NH 4 + efflux and OsVTC1-3-mediated protein N-glycosylation in rice grown under NH 4 + nutrition and identifies OsEIL1 as a direct genetic regulator of OsVTC1-3 expression.