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

ABSTRACT: 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. However, critical enzymes required for 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 S501 of NRT2.1, a residue that functions as a negative phospho-switch. CEPH is predominantly expressed in epidermal and cortex cells in roots and up-regulated by N starvation via a CEPDL2/CEPD1/2-mediated long-distance signaling from shoots. Loss of CEPH leads to a marked decrease in high-affinity nitrate uptake, tissue nitrate content, and plant biomass. Collectively, our results identify CEPH as a crucial enzyme in N starvation-dependent activation of NRT2.1, providing molecular and mechanistic insights into how plants regulate high-affinity nitrate uptake at the post-translational level in response to the N environment. We prepared total RNA from roots of wild type, CEPD1ox, CEPD2ox and CEPDL2ox plants grown on N-replete vertical plates for 14 d, and used a microarray analysis to identify genes specifically induced by CEPD family peptides.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE160649 | GEO | 2020/11/06

REPOSITORIES: GEO

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Project description:Arable soils are extremely heterogeneous in spatial nutrient distribution. It is well documented that lateral roots (LRs) proliferate in nitrate-rich patch. Yet less information is available as to which genes are involved in this process, in particular in cereals. To understand the molecular mechanism for local nitrate induced LR growth in maize (Zea mays L.), we analyzed the gene expression profiling in maize root in early response (1 hour) to local nitrate stimulation by using Maize Oligonucleotide Array (http://www.maizearray.org) and a split-root system. Selected differentially expressed genes were further confirmed by semi-quantitative RT-PCR. The results showed that reception and/or transduction of local NO3- signal involve some important protein kinases and protein phosphatases (histidine kinases, serine/threonine kinases, protein phosphatase 2A etc.) and transcription factors (F-box, Zinc finger, Myb and bZIP transcription factors and response regulator). Increasing expression of genes encoding auxin response factor 7b, ethylene receptor, and cytokinin oxidase suggests strong interaction among hormonal pathways and local NO3- signaling pathways. Genes involving NO3- uptake and assimilation (NRT2.1, NR, etc.), sugar transport (a sugar transporter) and utilization (a sucrose synthase) were enhanced in the N-fed root. Furthermore, local NO3- induces rapid expression of genes related to cell division and expansion such as alpha-expansin, celluose synthase, kinesin, plasma membrane and tonoplast aquaporins. Based on the differentially expressed genes, a putative model which combines both the 'NO3- signal' and 'metabolic sink' theories is proposed to explain the molecular mechanism controlling local nitrate induced LR elongation in maize. plants were pre-cultured in solution containing 0.5 mmol L-1 NO3- for 6 days and then transferred to N-free solution to grow for another 2 days. Then these plants were transferred to a two-compartment split-root system with only half root supplied with 1.0 mmol L-1 NO3-. Supply of Ca2+ in the N-free half was compensated by adding 1.0 mmol L-1 CaCl2. One hour after the local nitrate treatment, root segments (15cm from root tip to lateral root elongation zone) were sampled for RNA extraction. Two biological replicates were performed for each treatment.

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

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