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Post-Translational Modifications of Nitrate Reductases Autoregulates Nitric Oxide Biosynthesis in Arabidopsis.

ABSTRACT: Nitric oxide (NO) is a regulator of growth, development, and stress responses in living organisms. Plant nitrate reductases (NR) catalyze the reduction of nitrate to nitrite or, alternatively, to NO. In plants, NO action and its targets remain incompletely understood, and the way NO regulates its own homeostasis remains to be elucidated. A significant transcriptome overlapping between NO-deficient mutant and NO-treated wild type plants suggests that NO could negatively regulate its biosynthesis. A significant increase in NO content was detected in transgenic plants overexpressing NR1 and NR2 proteins. In turn, NR protein and activity as well as NO content, decreased in wild-type plants exposed to a pulse of NO gas. Tag-aided immunopurification procedures followed by tandem mass spectrometry allowed identifying NO-triggered post-translational modifications (PTMs) and ubiquitylation sites in NRs. Nitration of tyrosine residues and S-nitrosation of cysteine residues affected key amino acids involved in binding the essential FAD and molybdenum cofactors. NO-related PTMs were accompanied by ubiquitylation of lysine residues flanking the nitration and S-nitrosation sites. NO-induced PTMs of NRs potentially inhibit their activities and promote their proteasome-mediated degradation. This auto-regulatory feedback loop may control nitrate assimilation to ammonium and nitrite-derived production of NO under complex environmental conditions.

SUBMITTER: Costa-Broseta A

PROVIDER: S-EPMC7827142 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Post-Translational Modifications of Nitrate Reductases Autoregulates Nitric Oxide Biosynthesis in Arabidopsis.

Costa-Broseta Álvaro Á Castillo MariCruz M León José J

International journal of molecular sciences 20210107 2

Nitric oxide (NO) is a regulator of growth, development, and stress responses in living organisms. Plant nitrate reductases (NR) catalyze the reduction of nitrate to nitrite or, alternatively, to NO. In plants, NO action and its targets remain incompletely understood, and the way NO regulates its own homeostasis remains to be elucidated. A significant transcriptome overlapping between NO-deficient mutant and NO-treated wild type plants suggests that NO could negatively regulate its biosynthesis. ...[more]

PMID: 33430433

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Project description:ABA signaling relies on the perception of the hormone by 14 different members of the PYR/PYL/RCAR family of ABA receptors. Upon ABA binding, receptors become active in inhibiting a family of type 2C protein phosphatases that usually function as negative regulators on protein kinases of the SnRK2 family. Previous physiological and genetic data supporting a negative role exerted by nitric oxide (NO) on ABA signaling have been reported. Our preliminary data suggested that negative regulation exerted by NO on ABA signaling may involve direct effects of NO on ABA receptors. Here we explore whether the effects of NO on ABA signaling are due to post-translational modifications (PTMs) on ABA receptors. Two main PTMs are functionally related to NO, the S-nitrosylation of C residues and the nitration of Y residues and they have been studied in this work. Because our data suggest that NO can also modulate the stability of the receptor proteins, we have also analyzed another PTM, the ubiquitination of K residues. A double approach based on in vitro nitration of recombinant PYR/PYL/RCAR proteins as well as in planta expression of HA-tagged versions of the receptors, followed by immunopurification strategies based on anti-3-nitroY-coated magnetic beads, and LC-MS/MS analyses of the immunopurified proteins under non-reducing conditions allowed us to identify peptides containing nitroY (mass shifts of +45), S-nitrosylated C (mass shifts of +29), and K-GG tags resulting from the trypsin digestion of ubiquitin tails (mass shift of + 114). Our data suggest that S-nitrosylation of cysteines from PYR/PYL receptors occur in planta but has not effect on receptor function as tested in vitro. By contrast, the nitration of several Y residues of PYR/PYL receptors completely inactivates them, promotes also their polyubiquitination and marks them for subsequent proteasomal degradation, thus representing a rapid mechanism for lowering ABA sensitivity when required in the plant.

Project description:Nitrate reductases (NRs) are molybdoenzymes that reduce nitrate (NO3 -) to nitrite (NO2 -) in both mammals and plants. In mammals, the salival microbes take part in the generation of the NO2 - from NO3 -, which further produces nitric oxide (NO) either in acid-induced NO2 - reduction or in the presence of nitrite reductases (NiRs). Here, we report a new approach of VCl3 (V3+ ion source) induced step-wise reduction of NO3 - in a CoII-nitrato complex, [(12-TMC)CoII(NO3 -)]+ (2,{CoII-NO3 -}), to a CoIII-nitrosyl complex, [(12-TMC)CoIII(NO)]2+ (4,{CoNO}8), bearing an N-tetramethylated cyclam (TMC) ligand. The VCl3 inspired reduction of NO3 - to NO is believed to occur in two consecutive oxygen atom transfer (OAT) reactions, i.e., OAT-1 = NO3 - → NO2 - (r1) and OAT-2 = NO2 - → NO (r2). In these OAT reactions, VCl3 functions as an O-atom abstracting species, and the reaction of 2 with VCl3 produces a CoIII-nitrosyl ({CoNO}8) with VV-Oxo ({VV[double bond, length as m-dash]O}3+) species, via a proposed CoII-nitrito (3, {CoII-NO2 -}) intermediate species. Further, in a separate experiment, we explored the reaction of isolated complex 3 with VCl3, which showed the generation of 4 with VV-Oxo, validating our proposed reaction sequences of OAT reactions. We ensured and characterized 3 using VCl3 as a limiting reagent, as the second-order rate constant of OAT-2 (k 2 /) is found to be ∼1420 times faster than that of the OAT-1 (k 2) reaction. Binding constant (K b) calculations also support our proposition of NO3 - to NO transformation in two successive OAT reactions, as K b(CoII-NO2 -) is higher than K b(CoII-NO3 -), hence the reaction moves in the forward direction (OAT-1). However, K b(CoII-NO2 -) is comparable to K b{CoNO}8 , and therefore sequenced the second OAT reaction (OAT-2). Mechanistic investigations of these reactions using 15N-labeled-15NO3 - and 15NO2 - revealed that the N-atom in the {CoNO}8 is derived from NO3 - ligand. This work highlights the first-ever report of VCl3 induced step-wise NO3 - reduction (NRs activity) followed by the OAT induced NO2 - reduction and then the generation of Co-nitrosyl species {CoNO}8.

Dataset Information

Post-Translational Modifications of Nitrate Reductases Autoregulates Nitric Oxide Biosynthesis in Arabidopsis.

Publications

Post-Translational Modifications of Nitrate Reductases Autoregulates Nitric Oxide Biosynthesis in Arabidopsis.

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