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Nitric oxide-fixation in plants: A new pathway enabling the use of nitric oxide as nitrogen source

ABSTRACT: Of all the essential nutrients, nitrogen is the one most often limiting for plant growth. Nitrogen can be taken up by plants in two ways. One possibility is through ammonium and nitrate, which are the predominate inorganic forms of nitrogen in soils. The second possibility is the uptake of air-born nitrogen through plant-associated mircoorganisms in root nodules. The majority of plants able to form such nitrogen-fixing root nodules are in the legume family Fabaceae. Here we present a third possibility – a new pathway, termed as nitric oxide (NO)-fixation pathway, which allows plants to fix atmospheric NO and to use it for better growth and development. We identified non-symbiotic hemoglobin class 1 (AtGLB1) and class 2 (AtGLB2) as key proteins of the NO-fixation pathway. In an NO enriched environment NO-fixation is enhanced considerably in plants overexpressing AtGLB1 or AtGLB2 genes. NO uptake resulted in four-fold higher nitrate levels in these plants compared to NO-treated wild-type plants. Correspondingly, the growth parameters like rosettes size and weight, vegetative shoot thickness and also seed yield were 25%, 40%, 30%, and 20% higher, respectively, in the overexpression lines in comparison to wild-type plants. Our results highlight the existence of a NO-fixing pathway in plants. We demonstrated that plant non-symbiotic hemoglobin proteins can fix atmospheric NO and convert it to nitrate, which is further introduced into the N-metabolism. We assume that our results might provide new insights into the field of crop science research and that the NO-fixation capability might serve as a new economically important breeding trait for enhancing biomass, fruit, and seed production. Modifying this pathway might be a promising approach for better and more environment-friendly supply of nitrogen. For example crop plant hemoglobin proteins could be improved for their NO-fixing capability and their expression levels could be increased.

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE45576 | GEO | 2013/09/01

SECONDARY ACCESSION(S): PRJNA194611

REPOSITORIES: GEO

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Project description:Of all the essential nutrients, nitrogen is the one most often limiting for plant growth. Nitrogen can be taken up by plants in two ways. One possibility is through ammonium and nitrate, which are the predominate inorganic forms of nitrogen in soils. The second possibility is the uptake of air-born nitrogen through plant-associated mircoorganisms in root nodules. The majority of plants able to form such nitrogen-fixing root nodules are in the legume family Fabaceae. Here we present a third possibility M-bM-^@M-^S a new pathway, termed as nitric oxide (NO)-fixation pathway, which allows plants to fix atmospheric NO and to use it for better growth and development. We identified non-symbiotic hemoglobin class 1 (AtGLB1) and class 2 (AtGLB2) as key proteins of the NO-fixation pathway. In an NO enriched environment NO-fixation is enhanced considerably in plants overexpressing AtGLB1 or AtGLB2 genes. NO uptake resulted in four-fold higher nitrate levels in these plants compared to NO-treated wild-type plants. Correspondingly, the growth parameters like rosettes size and weight, vegetative shoot thickness and also seed yield were 25%, 40%, 30%, and 20% higher, respectively, in the overexpression lines in comparison to wild-type plants. Our results highlight the existence of a NO-fixing pathway in plants. We demonstrated that plant non-symbiotic hemoglobin proteins can fix atmospheric NO and convert it to nitrate, which is further introduced into the N-metabolism. We assume that our results might provide new insights into the field of crop science research and that the NO-fixation capability might serve as a new economically important breeding trait for enhancing biomass, fruit, and seed production. Modifying this pathway might be a promising approach for better and more environment-friendly supply of nitrogen. For example crop plant hemoglobin proteins could be improved for their NO-fixing capability and their expression levels could be increased. WT-Arabidopsis thaliana plants were fumigated with Ambient NO and 3 ppm NO air in three completely independent biological experiments. Total RNA was isolated from four-week old rosette leaves of these plants to determine the gene expression signature of each samples using Agilent one-color microarray. Differences in the gene expression signatures between Ambient NO and 3 ppm NO treated samples were analyzed to see the effect of NO fumigation on the WT Arabidopsis plants at the transcript level.

Project description:Resendis-Antonio2007 - Genome-scale metabolic network of Rhizobium etli (iOR363) This model is described in the article: Metabolic reconstruction and modeling of nitrogen fixation in Rhizobium etli. Resendis-Antonio O, Reed JL, Encarnación S, Collado-Vides J, Palsson BØ. PLoS Comput. Biol. 2007 Oct; 3(10): 1887-1895 Abstract: Rhizobiaceas are bacteria that fix nitrogen during symbiosis with plants. This symbiotic relationship is crucial for the nitrogen cycle, and understanding symbiotic mechanisms is a scientific challenge with direct applications in agronomy and plant development. Rhizobium etli is a bacteria which provides legumes with ammonia (among other chemical compounds), thereby stimulating plant growth. A genome-scale approach, integrating the biochemical information available for R. etli, constitutes an important step toward understanding the symbiotic relationship and its possible improvement. In this work we present a genome-scale metabolic reconstruction (iOR363) for R. etli CFN42, which includes 387 metabolic and transport reactions across 26 metabolic pathways. This model was used to analyze the physiological capabilities of R. etli during stages of nitrogen fixation. To study the physiological capacities in silico, an objective function was formulated to simulate symbiotic nitrogen fixation. Flux balance analysis (FBA) was performed, and the predicted active metabolic pathways agreed qualitatively with experimental observations. In addition, predictions for the effects of gene deletions during nitrogen fixation in Rhizobia in silico also agreed with reported experimental data. Overall, we present some evidence supporting that FBA of the reconstructed metabolic network for R. etli provides results that are in agreement with physiological observations. Thus, as for other organisms, the reconstructed genome-scale metabolic network provides an important framework which allows us to compare model predictions with experimental measurements and eventually generate hypotheses on ways to improve nitrogen fixation. This model is hosted on BioModels Database and identified by: MODEL1507180006. To cite BioModels Database, please use: BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

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Nitric oxide-fixation in plants: A new pathway enabling the use of nitric oxide as nitrogen source

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