A type 2C protein phosphatase activates high-affinity nitrate uptake by dephosphorylating NRT2.1

The nitrate transporter NRT2.1, which plays a central role in high-affinity nitrate uptake in roots, is activated at the post-translational level in response to nitrogen (N) starvation(1,2). However, the critical enzymes required for the post-translational activation of NRT2.1 remain to be identified. Here, we show that a type 2C protein phosphatase, designated CEPD-induced phosphatase (CEPH), activates high-affinity nitrate uptake by directly dephosphorylating Ser501 of NRT2.1, a residue that functions as a negative phospho-switch in Arabidopsis(2). CEPH is predominantly expressed in epidermal and cortex cells in roots and is upregulated by N starvation via a CEPDL2/CEPD1/2-mediated long-distance signalling from shoots(3,4). The loss of CEPH leads to marked decreases in high-affinity nitrate uptake, tissue nitrate content and plant biomass. Collectively, our results identify CEPH as a crucial enzyme in the N-starvation-dependent activation of NRT2.1 and provide molecular and mechanistic insights into how plants regulate high-affinity nitrate uptake at the post-translational level in response to the N environment. Systemic nitrogen signalling controls root nitrogen acquisition. The regulatory pathways involve the CEP-CEPD network and the high-affinity nitrate transporter NRT2.1. In this study, the authors identified CEPH, a type 2C protein phosphatase, acting downstream of the CEPD/CEPDLs to regulate the activity of NRT2.1 and nitrate uptake in Arabidopsis.

Automated summary

CEPH, a type 2C protein phosphatase, is identified as a crucial enzyme in the N-starvation-dependent activation of NRT2.1, directly dephosphorylating Ser501 to activate high-affinity nitrate uptake in Arabidopsis. CEPH is mainly expressed in epidermal and cortex cells in roots, upregulated by N starvation via a long-distance signaling from shoots mediated by CEPDL2/CEPD1/2. Loss of CEPH leads to decreased nitrate uptake, tissue nitrate content, and plant biomass.