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Soba D, Arrese-Igor C, Aranjuelo I. Additive effects of heatwave and water stresses on soybean seed yield is caused by impaired carbon assimilation at pod formation but not at flowering. Plant Sci 2022; 321:111320. [PMID: 35696920 DOI: 10.1016/j.plantsci.2022.111320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2022] [Revised: 04/06/2022] [Accepted: 05/10/2022] [Indexed: 06/15/2023]
Abstract
Heatwave (HW) combined with water stress (WS) are critical environmental factors negatively affecting crop development. This study aimed to quantify the individual and combined effects of HW and WS during early reproductive stages on leaf and nodule functioning and their relation with final soybean seed yield (SY). For this purpose, during flowering (R2) and pod formation (R4) soybean (Glycine max L. Merr.) plants were exposed to different temperature (ambient[25ºC] versus HW[40ºC]) and water availability (full capacity versus WS[20% field capacity]). HW, WS and their combined impact on yield depended on the phenological stage at which stress was applied being more affected at R4. For gas exchange, WS severely impaired photosynthetic machinery, especially when combined with HS. Impaired photoassimilate supply at flowering caused flower abortion and a significant reduction in final SY due to interacting stresses and WS. On the other hand, at pod formation (R4), decreased leaf performance caused additive effect on SY by decreasing pod setting and seed size with combined stresses. At the nodule level, WS (alone or in combination with HW) caused nodule impairment, which was reflected by lower leaf N. Such response was linked with a poor malate supply to bacteroids and feed-back inhibition caused by nitrogenous compounds accumulation. In summary, our study noted that soybean sensitivity to interacting heat and water stresses was highly conditioned by the phenological stage at which it occurs with, R4 stage being the critical moment. To our knowledge this is the first soybean work integrating combined stresses at early reproductive stages.
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Affiliation(s)
- David Soba
- Instituto de Agrobiotecnología (IdAB), Consejo Superior de Investigaciones Científicas (CSIC)-Gobierno de Navarra, Av. Pamplona 123, 31192 Mutilva, Spain
| | - Cesar Arrese-Igor
- Institute for Multidisciplinary Research in Applied Biology (IMAB), Universidad Pública de Navarra (UPNa), Campus Arrosadia, 31006 Pamplona, Spain
| | - Iker Aranjuelo
- Instituto de Agrobiotecnología (IdAB), Consejo Superior de Investigaciones Científicas (CSIC)-Gobierno de Navarra, Av. Pamplona 123, 31192 Mutilva, Spain.
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Cobos-Porras L, Rubia MI, Huertas R, Kum D, Dalton DA, Udvardi MK, Arrese-Igor C, Larrainzar E. Increased Ascorbate Biosynthesis Does Not Improve Nitrogen Fixation Nor Alleviate the Effect of Drought Stress in Nodulated Medicago truncatula Plants. Front Plant Sci 2021; 12:686075. [PMID: 34262586 PMCID: PMC8273863 DOI: 10.3389/fpls.2021.686075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 06/03/2021] [Indexed: 06/13/2023]
Abstract
Legume plants are able to establish nitrogen-fixing symbiotic relations with Rhizobium bacteria. This symbiosis is, however, affected by a number of abiotic constraints, particularly drought. One of the consequences of drought stress is the overproduction of reactive oxygen (ROS) and nitrogen species (RNS), leading to cellular damage and, ultimately, cell death. Ascorbic acid (AsA), also known as vitamin C, is one of the antioxidant compounds that plants synthesize to counteract this oxidative damage. One promising strategy for the improvement of plant growth and symbiotic performance under drought stress is the overproduction of AsA via the overexpression of enzymes in the Smirnoff-Wheeler biosynthesis pathway. In the current work, we generated Medicago truncatula plants with increased AsA biosynthesis by overexpressing MtVTC2, a gene coding for GDP-L-galactose phosphorylase. We characterized the growth and physiological responses of symbiotic plants both under well-watered conditions and during a progressive water deficit. Results show that increased AsA availability did not provide an advantage in terms of plant growth or symbiotic performance either under well-watered conditions or in response to drought.
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Affiliation(s)
- Libertad Cobos-Porras
- Institute for Multidisciplinary Applied Biology (IMAB), Universidad Pública de Navarra (UPNA), Pamplona, Spain
| | - María Isabel Rubia
- Institute for Multidisciplinary Applied Biology (IMAB), Universidad Pública de Navarra (UPNA), Pamplona, Spain
| | - Raúl Huertas
- Plant Biology Division, Noble Research Institute LLC, Ardmore, OK, United States
| | - David Kum
- Biology Department, Reed College, Portland, OR, United States
| | - David A. Dalton
- Biology Department, Reed College, Portland, OR, United States
| | - Michael K. Udvardi
- Plant Biology Division, Noble Research Institute LLC, Ardmore, OK, United States
| | - Cesar Arrese-Igor
- Institute for Multidisciplinary Applied Biology (IMAB), Universidad Pública de Navarra (UPNA), Pamplona, Spain
| | - Estíbaliz Larrainzar
- Institute for Multidisciplinary Applied Biology (IMAB), Universidad Pública de Navarra (UPNA), Pamplona, Spain
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Rubia MI, Ramachandran VK, Arrese-Igor C, Larrainzar E, Poole PS. A novel biosensor to monitor proline in pea root exudates and nodules under osmotic stress and recovery. Plant Soil 2020; 452:413-422. [PMID: 32713966 PMCID: PMC7371648 DOI: 10.1007/s11104-020-04577-2] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 05/19/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND AND AIMS Plant and bacteria are able to synthesise proline, which acts as a compound to counteract the negative effects of osmotic stresses. Most methodologies rely on the extraction of compounds using destructive methods. This work describes a new proline biosensor that allows the monitoring of proline levels in a non-invasive manner in root exudates and nodules of legume plants. METHODS The proline biosensor was constructed by cloning the promoter region of pRL120553, a gene with high levels of induction in the presence of proline, in front of the lux cassette in Rhizobium leguminosarum bv. viciae. RESULTS Free-living assays show that the proline biosensor is sensitive and specific for proline. Proline was detected in both root exudates and nodules of pea plants. The luminescence detected in bacteroids did not show variations during osmotic stress treatments, but significantly increased during recovery. CONCLUSIONS This biosensor is a useful tool for the in vivo monitoring of proline levels in root exudates and bacteroids of symbiotic root nodules, and it contributes to our understanding of the metabolic exchange occurring in nodules under abiotic stress conditions.
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Affiliation(s)
- María I. Rubia
- Institute for Multidisciplinary Research in Applied Biology-IMAB, Universidad Pública de Navarra, Campus Arrosadia, Pamplona, 31006 Spain
| | | | - Cesar Arrese-Igor
- Institute for Multidisciplinary Research in Applied Biology-IMAB, Universidad Pública de Navarra, Campus Arrosadia, Pamplona, 31006 Spain
| | - Estíbaliz Larrainzar
- Institute for Multidisciplinary Research in Applied Biology-IMAB, Universidad Pública de Navarra, Campus Arrosadia, Pamplona, 31006 Spain
| | - Philip S. Poole
- Department of Plant Sciences, University of Oxford, Oxford, OX1 3RB UK
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Soba D, Zhou B, Arrese-Igor C, Munné-Bosch S, Aranjuelo I. Physiological, Hormonal and Metabolic Responses of two Alfalfa Cultivars with Contrasting Responses to Drought. Int J Mol Sci 2019; 20:E5099. [PMID: 31618819 PMCID: PMC6829892 DOI: 10.3390/ijms20205099] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/13/2019] [Accepted: 10/14/2019] [Indexed: 12/17/2022] Open
Abstract
Alfalfa (Medicago sativa L.) is frequently constrained by environmental conditions such as drought. Within this context, it is crucial to identify the physiological and metabolic traits conferring a better performance under stressful conditions. In the current study, two alfalfa cultivars (San Isidro and Zhong Mu) with different physiological strategies were selected and subjected to water limitation conditions. Together with the physiological analyses, we proceeded to characterize the isotopic, hormone, and metabolic profiles of the different plants. According to physiological and isotopic data, Zhong Mu has a water-saver strategy, reducing water lost by closing its stomata but fixing less carbon by photosynthesis, and therefore limiting its growth under water-stressed conditions. In contrast, San Isidro has enhanced root growth to replace the water lost through transpiration due to its more open stomata, thus maintaining its biomass. Zhong Mu nodules were less able to maintain nodule N2 fixing activity (matching plant nitrogen (N) demand). Our data suggest that this cultivar-specific performance is linked to Asn accumulation and its consequent N-feedback nitrogenase inhibition. Additionally, we observed a hormonal reorchestration in both cultivars under drought. Therefore, our results showed an intra-specific response to drought at physiological and metabolic levels in the two alfalfa cultivars studied.
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Affiliation(s)
- David Soba
- Instituto de Agrobiotecnología (IdAB), Consejo Superior de Investigaciones Científicas-Gobierno de Navarra, 31006 Mutilva, Spain.
| | - Bangwei Zhou
- Key Laboratory of Vegetation Ecology, Ministry of Education, Institute of Grassland Science, Northeast Normal University, Changchun 130024, China.
| | - Cesar Arrese-Igor
- Department of Sciences, Institute for Multidisciplinary Research in Applied Biology, Universidad Pública de Navarra, E-31006 Pamplona, Spain.
| | - Sergi Munné-Bosch
- Department of Evolutionary Biology, Ecology and Environmental Sciences, Faculty of Biology, University of Barcelona, 08028 Barcelona, Spain.
| | - Iker Aranjuelo
- Instituto de Agrobiotecnología (IdAB), Consejo Superior de Investigaciones Científicas-Gobierno de Navarra, 31006 Mutilva, Spain.
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Iturralde ET, Covelli JM, Alvarez F, Pérez-Giménez J, Arrese-Igor C, Lodeiro AR. Soybean-Nodulating Strains With Low Intrinsic Competitiveness for Nodulation, Good Symbiotic Performance, and Stress-Tolerance Isolated From Soybean-Cropped Soils in Argentina. Front Microbiol 2019; 10:1061. [PMID: 31139173 PMCID: PMC6527597 DOI: 10.3389/fmicb.2019.01061] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 04/26/2019] [Indexed: 01/04/2023] Open
Abstract
Soybean is the most important oilseed in the world, cropped in 120–130 million hectares each year. The three most important soybean producers are Argentina, Brazil, and United States, where soybean crops are routinely inoculated with symbiotic N2-fixing Bradyrhizobium spp. This extended inoculation gave rise to soybean-nodulating allochthonous populations (SNAPs) that compete against new inoculant for nodulation, thus impairing yield responses. Competitiveness depends on intrinsic factors contributed by genotype, extrinsic ones determined by growth and environmental conditions, and strain persistence in the soil. To assess these factors in Argentinean SNAPs, we studied 58 isolates from five sites of the main soybean cropping area. BOX-A1R DNA fingerprint distributed these isolates in 10 clades that paralleled the pHs of their original soils. By contrast, reference Bradyrhizobium spp. strains, including those used as soybean-inoculants, were confined to a single clade. More detailed characterization of a subset of 11 SNAP-isolates revealed that five were Bradyrhizobium japonicum, two Bradyrhizobium elkanii, two Rhizobium radiobacter (formerly Agrobacterium tumefaciens), one Bradyrhizobium diazoefficiens, and one Paenibacillus glycanilyticus-which did not nodulate when inoculated alone, and therefore was excluded from further characterization. The remaining subset of 10 SNAP-isolates was used for deeper characterization. All SNAP-isolates were aluminum- and heat-tolerant, and most of them were glyphosate-tolerant. Meanwhile, inoculant strains tested were sensitive to aluminum and glyphosate. In addition, all SNAP-isolates were motile to different degrees. Only three SNAP-isolates were deficient for N2-fixation, and none was intrinsically more competitive than the inoculant strain. These results are in contrast to the general belief that rhizobia from soil populations evolved as intrinsically more competitive for nodulation and less N2-fixing effective than inoculants strains. Shoot:root ratios, both as dry biomass and as total N, were highly correlated with leaf ureide contents, and therefore may be easy indicators of N2-fixing performance, suggesting that highly effective N2-fixing and well-adapted strains may be readily selected from SNAPs. In addition, intrinsic competitiveness of the inoculants strains seems already optimized against SNAP strains, and therefore our efforts to improve nodules occupation by inoculated strains should focus on the optimization of extrinsic competitiveness factors, such as inoculant formulation and inoculation technology.
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Affiliation(s)
- Esteban T Iturralde
- Facultad de Ciencias Exactas, Instituto de Biotecnología y Biología Molecular (IBBM), UNLP y CCT La Plata-CONICET, La Plata, Argentina
| | - Julieta M Covelli
- Facultad de Ciencias Exactas, Instituto de Biotecnología y Biología Molecular (IBBM), UNLP y CCT La Plata-CONICET, La Plata, Argentina
| | - Florencia Alvarez
- Facultad de Ciencias Exactas, Instituto de Biotecnología y Biología Molecular (IBBM), UNLP y CCT La Plata-CONICET, La Plata, Argentina
| | - Julieta Pérez-Giménez
- Facultad de Ciencias Exactas, Instituto de Biotecnología y Biología Molecular (IBBM), UNLP y CCT La Plata-CONICET, La Plata, Argentina
| | - Cesar Arrese-Igor
- Institute for Multidisciplinary Research in Applied Biology (IMAB), Universidad Pública de Navarra, Pamplona, Spain
| | - Aníbal R Lodeiro
- Facultad de Ciencias Exactas, Instituto de Biotecnología y Biología Molecular (IBBM), UNLP y CCT La Plata-CONICET, La Plata, Argentina
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Aranjuelo I, Molero G, Erice G, Aldasoro J, Arrese-Igor C, Nogués S. Effect of shoot removal on remobilization of carbon and nitrogen during regrowth of nitrogen-fixing alfalfa. Physiol Plant 2015; 153:91-104. [PMID: 24813428 DOI: 10.1111/ppl.12222] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 03/27/2014] [Accepted: 03/27/2014] [Indexed: 05/27/2023]
Abstract
The contribution of carbon and nitrogen reserves to regrowth following shoot removal has been studied in the past. However, important gaps remain in understanding the effect of shoot cutting on nodule performance and its relevance during regrowth. In this study, isotopic labelling was conducted at root and canopy levels with both (15) N2 and (13) C-depleted CO2 on exclusively nitrogen-fixing alfalfa plants. As expected, our results indicate that the roots were the main sink organs before shoots were removed. Seven days after regrowth the carbon and nitrogen stored in the roots was invested in shoot biomass formation and partitioned to the nodules. The large depletion in nodule carbohydrate availability suggests that root-derived carbon compounds were delivered towards nodules in order to sustain respiratory activity. In addition to the limited carbohydrate availability, the upregulation of nodule peroxidases showed that oxidative stress was also involved during poor nodule performance. Fourteen days after cutting, and as a consequence of the stimulated photosynthetic and N2 -fixing machinery, availability of Cnew and Nnew strongly diminished in the plants due to their replacement by C and N assimilated during the post-labelling period. In summary, our study indicated that during the first week of regrowth, root-derived C and N remobilization did not overcome C- and N-limitation in nodules and leaves. However, 14 days after cutting, leaf and nodule performance were re-established.
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Affiliation(s)
- Iker Aranjuelo
- Instituto de Agrobiotecnología (IdAB), Universidad Pública de Navarra-CSIC-Gobierno de Navarra, ES-31192, Mutilva Baja, Spain; Unitat de Fisologia Vegetal, Facultat de Biologia, Universitat de Barcelona, ES-08028, Barcelona, Spain
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Larrainzar E, Gil-Quintana E, Arrese-Igor C, González EM, Marino D. Split-root systems applied to the study of the legume-rhizobial symbiosis: what have we learned? J Integr Plant Biol 2014; 56:1118-24. [PMID: 24975457 DOI: 10.1111/jipb.12231] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Accepted: 06/22/2014] [Indexed: 05/28/2023]
Abstract
Split-root system (SRS) approaches allow the differential treatment of separate and independent root systems, while sharing a common aerial part. As such, SRS is a useful tool for the discrimination of systemic (shoot origin) versus local (root/nodule origin) regulation mechanisms. This type of approach is particularly useful when studying the complex regulatory mechanisms governing the symbiosis established between legumes and Rhizobium bacteria. The current work provides an overview of the main insights gained from the application of SRS approaches to understand how nodule number (nodulation autoregulation) and nitrogen fixation are controlled both under non-stressful conditions and in response to a variety of stresses. Nodule number appears to be mainly controlled at the systemic level through a signal which is produced by nodule/root tissue, translocated to the shoot, and transmitted back to the root system, involving shoot Leu-rich repeat receptor-like kinases. In contrast, both local and systemic mechanisms have been shown to operate for the regulation of nitrogenase activity in nodules. Under drought and heavy metal stress, the regulation is mostly local, whereas the application of exogenous nitrogen seems to exert a regulation of nitrogen fixation both at the local and systemic levels.
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Affiliation(s)
- Estíbaliz Larrainzar
- Department of Environmental Sciences, Public University of Navarra, Pamplona, E-31006, Spain
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Irar S, González EM, Arrese-Igor C, Marino D. A proteomic approach reveals new actors of nodule response to drought in split-root grown pea plants. Physiol Plant 2014; 152:634-45. [PMID: 24754352 DOI: 10.1111/ppl.12214] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Revised: 03/12/2014] [Accepted: 03/19/2014] [Indexed: 05/21/2023]
Abstract
Drought is considered the more harmful abiotic stress resulting in crops yield loss. Legumes in symbiosis with rhizobia are able to fix atmospheric nitrogen. Biological nitrogen fixation (SNF) is a very sensitive process to drought and limits legumes agricultural productivity. Several factors are known to regulate SNF including oxygen availability to bacteroids, carbon and nitrogen metabolisms; but the signaling pathways leading to SNF inhibition are largely unknown. In this work, we have performed a proteomic approach of pea plants grown in split-root system where one half of the root was well-irrigated and the other was subjected to drought. Water stress locally provoked nodule water potential decrease that led to SNF local inhibition. The proteomic approach revealed 11 and 7 nodule proteins regulated by drought encoded by Pisum sativum and Rhizobium leguminosarum genomes respectively. Among these 18 proteins, 3 proteins related to flavonoid metabolism, 2 to sulfur metabolism and 3 RNA-binding proteins were identified. These proteins could be molecular targets for future studies focused on the improvement of legumes tolerance to drought. Moreover, this work also provides new hints for the deciphering of SNF regulation machinery in nodules.
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Affiliation(s)
- Sami Irar
- Servicio de Proteómica y Metabolómica, CRAG - Centre de Recerca en Agrigenòmica - CSIC IRTA UAB UB, Campus UAB, Edifici CRAG, Bellaterra (Cerdenyola del Valles), 08193, Barcelona, Spain
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Larrainzar E, Molenaar JA, Wienkoop S, Gil-Quintana E, Alibert B, Limami AM, Arrese-Igor C, González EM. Drought stress provokes the down-regulation of methionine and ethylene biosynthesis pathways in Medicago truncatula roots and nodules. Plant Cell Environ 2014; 37:2051-63. [PMID: 24471423 DOI: 10.1111/pce.12285] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 01/19/2014] [Indexed: 05/04/2023]
Abstract
Symbiotic nitrogen fixation is one of the first physiological processes inhibited in legume plants under water-deficit conditions. Despite the progress made in the last decades, the molecular mechanisms behind this regulation are not fully understood yet. Recent proteomic work carried out in the model legume Medicago truncatula provided the first indications of a possible involvement of nodule methionine (Met) biosynthesis and related pathways in response to water-deficit conditions. To better understand this involvement, the drought-induced changes in expression and content of enzymes involved in the biosynthesis of Met, S-adenosyl-L-methionine (SAM) and ethylene in M. truncatula root and nodules were analyzed using targeted approaches. Nitrogen-fixing plants were subjected to a progressive water deficit and a subsequent recovery period. Besides the physiological characterization of the plants, the content of total sulphur, sulphate and main S-containing metabolites was measured. Results presented here show that S availability is not a limiting factor in the drought-induced decline of nitrogen fixation rates in M. truncatula plants and provide evidences for a down-regulation of the Met and ethylene biosynthesis pathways in roots and nodules in response to water-deficit conditions.
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Affiliation(s)
- Estíbaliz Larrainzar
- Dpto. Ciencias del Medio Natural, Universidad Pública de Navarra, 31006, Pamplona, Spain
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Larrainzar E, Gil-Quintana E, Seminario A, Arrese-Igor C, González EM. Nodule carbohydrate catabolism is enhanced in the Medicago truncatula A17-Sinorhizobium medicae WSM419 symbiosis. Front Microbiol 2014; 5:447. [PMID: 25221545 PMCID: PMC4145349 DOI: 10.3389/fmicb.2014.00447] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Accepted: 08/05/2014] [Indexed: 12/22/2022] Open
Abstract
The symbiotic association between Medicago truncatula and Sinorhizobium meliloti is a well-established model system in the legume–Rhizobium community. Despite its wide use, the symbiotic efficiency of this model has been recently questioned and an alternative microsymbiont, S. medicae, has been proposed. However, little is known about the physiological mechanisms behind the higher symbiotic efficiency of S. medicae WSM419. In the present study, we inoculated M. truncatula Jemalong A17 with either S. medicae WSM419 or S. meliloti 2011 and compared plant growth, photosynthesis, N2-fixation rates, and plant nodule carbon and nitrogen metabolic activities in the two systems. M. truncatula plants in symbiosis with S. medicae showed increased biomass and photosynthesis rates per plant. Plants grown in symbiosis with S. medicae WSM419 also showed higher N2-fixation rates, which were correlated with a larger nodule biomass, while nodule number was similar in both systems. In terms of plant nodule metabolism, M. truncatula–S. medicae WSM419 nodules showed increased sucrose-catabolic activity, mostly associated with sucrose synthase, accompanied by a reduced starch content, whereas nitrogen-assimilation activities were comparable to those measured in nodules infected with S. meliloti 2011. Taken together, these results suggest that S. medicae WSM419 is able to enhance plant carbon catabolism in M. truncatula nodules, which allows for the maintaining of high symbiotic N2-fixation rates, better growth and improved general plant performance.
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Affiliation(s)
- Estíbaliz Larrainzar
- Departamento de Ciencias del Medio Natural/Environmental Sciences, Universidad Pública de Navarra Pamplona, Spain
| | - Erena Gil-Quintana
- Departamento de Ciencias del Medio Natural/Environmental Sciences, Universidad Pública de Navarra Pamplona, Spain
| | - Amaia Seminario
- Departamento de Ciencias del Medio Natural/Environmental Sciences, Universidad Pública de Navarra Pamplona, Spain
| | - Cesar Arrese-Igor
- Departamento de Ciencias del Medio Natural/Environmental Sciences, Universidad Pública de Navarra Pamplona, Spain
| | - Esther M González
- Departamento de Ciencias del Medio Natural/Environmental Sciences, Universidad Pública de Navarra Pamplona, Spain
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Aranjuelo I, Arrese-Igor C, Molero G. Nodule performance within a changing environmental context. J Plant Physiol 2014; 171:1076-90. [PMID: 24974334 DOI: 10.1016/j.jplph.2014.04.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Revised: 04/01/2014] [Accepted: 04/02/2014] [Indexed: 05/09/2023]
Abstract
Global climate models predict that future environmental conditions will see alterations in temperature, water availability and CO2 concentration ([CO2]) in the atmosphere. Climate change will reinforce the need to develop highly productive crops. For this purpose it is essential to identify target traits conditioning plant performance in changing environments. N2 fixing plants represent the second major crop of agricultural importance worldwide. The current review provides a compilation of results from existing literature on the effects of several abiotic stress conditions on nodule performance and N2 fixation. The environmental factors analysed include water stress, salinity, temperature, and elevated [CO2]. Despite the large number of studies analysing [CO2] effects in plants, frequently they have been conducted under optimal growth conditions that are difficult to find in natural conditions where different stresses often occur simultaneously. This is why we have also included a section describing the current state of knowledge of interacting environmental conditions in nodule functioning. Regardless of the environmental factor considered, it is evident that some general patterns of nodule response are observed. Nodule carbohydrate and N compound availability, together with the presence of oxygen reactive species (ROS) have proven to be the key factors modulating N2 fixation at the physiological/biochemical levels. However, with the exception of water availability and [CO2], it should also be considered that nodule performance has not been characterised in detail under other limiting growth conditions. This highlights the necessity to conduct further studies considering these factors. Finally, we also observe that a better understanding of these metabolic effects of changing environment in nodule functioning would require an integrated and synergistic investigation based on widely used and novel protocols such as transcriptomics, proteomics, metabolomics and stable isotopes.
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Affiliation(s)
- Iker Aranjuelo
- Instituto de Agrobiotecnología, Universidad Pública de Navarra-CSIC-Gobierno de Navarra, Campus de Arrosadía, E-31192 Mutilva Baja, Spain.
| | - Cesar Arrese-Igor
- Dpto. Ciencias del Medio Natural, Universidad Pública de Navarra, Instituto de Agrobiotecnología, Universidad Pública de Navarra-CSIC-Gobierno de Navarra, Campus de Arrosadía, E-31006 Pamplona, Spain
| | - Gemma Molero
- International Maize and Wheat Improvement Center (CIMMYT), El Batán, Texcoco CP 56130, Mexico
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Gil-Quintana E, Larrainzar E, Seminario A, Díaz-Leal JL, Alamillo JM, Pineda M, Arrese-Igor C, Wienkoop S, González EM. Local inhibition of nitrogen fixation and nodule metabolism in drought-stressed soybean. J Exp Bot 2013; 64:2171-82. [PMID: 23580751 PMCID: PMC3654410 DOI: 10.1093/jxb/ert074] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Drought stress is a major factor limiting symbiotic nitrogen fixation (NF) in soybean crop production. However, the regulatory mechanisms involved in this inhibition are still controversial. Soybean plants were symbiotically grown in a split-root system (SRS), which allowed for half of the root system to be irrigated at field capacity while the other half remained water deprived. NF declined in the water-deprived root system while nitrogenase activity was maintained at control values in the well-watered half. Concomitantly, amino acids and ureides accumulated in the water-deprived belowground organs regardless of transpiration rates. Ureide accumulation was found to be related to the decline in their degradation activities rather than increased biosynthesis. Finally, proteomic analysis suggests that plant carbon metabolism, protein synthesis, amino acid metabolism, and cell growth are among the processes most altered in soybean nodules under drought stress. Results presented here support the hypothesis of a local regulation of NF taking place in soybean and downplay the role of ureides in the inhibition of NF.
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Affiliation(s)
- Erena Gil-Quintana
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain
| | - Estíbaliz Larrainzar
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain
- Department of Plant Pathology, University of California-Davis, One Shields Avenue, Davis, CA95616, USA
| | - Amaia Seminario
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain
| | - Juan Luis Díaz-Leal
- Departamento de Botánica, Ecología y Fisiología Vegetal, CEIA3. Universidad de Córdoba, 14071 Córdoba, Spain
| | - Josefa M. Alamillo
- Departamento de Botánica, Ecología y Fisiología Vegetal, CEIA3. Universidad de Córdoba, 14071 Córdoba, Spain
| | - Manuel Pineda
- Departamento de Botánica, Ecología y Fisiología Vegetal, CEIA3. Universidad de Córdoba, 14071 Córdoba, Spain
| | - Cesar Arrese-Igor
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain
| | - Stefanie Wienkoop
- Department of Molecular Systems Biology, University of Vienna, Althanstrasse 14, 1090 Vienna, Austria
| | - Esther M. González
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain
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Gil-Quintana E, Larrainzar E, Arrese-Igor C, González EM. Is N-feedback involved in the inhibition of nitrogen fixation in drought-stressed Medicago truncatula? J Exp Bot 2013; 64:281-92. [PMID: 23175536 PMCID: PMC3528036 DOI: 10.1093/jxb/ers334] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Drought stress is a major factor limiting nitrogen fixation (NF) in crop production. However, the regulatory mechanism involved and the origin of the inhibition, whether local or systemic, is still controversial and so far scarcely studied in temperate forage legumes. Medicago truncatula plants were symbiotically grown with a split-root system and exposed to gradual water deprivation. Physiological parameters, NF activity, and amino acid content were measured. The partial drought treatment inhibited NF in the nodules directly exposed to drought stress. Concomitantly, in the droughted below-ground organs, amino acids accumulated prior to any drop in evapotranspiration (ET). It is concluded that drought exerts a local inhibition of NF and drives an overall accumulation of amino acids in diverse plant organs which is independent of the decrease in ET. The general increase in the majority of single amino acids in the whole plant questions the commonly accepted concept of a single amino acid acting as an N-feedback signal.
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Affiliation(s)
- Erena Gil-Quintana
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain
| | - Estíbaliz Larrainzar
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain
- Department of Plant Pathology, University of California, One Shields Avenue, Davis, CA 95616, USA
| | - Cesar Arrese-Igor
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain
| | - Esther M. González
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, 31006 Pamplona, Spain
- * To whom correspondence should be addressed. E-mail:
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Talbi C, Sánchez C, Hidalgo-Garcia A, González EM, Arrese-Igor C, Girard L, Bedmar EJ, Delgado MJ. Enhanced expression of Rhizobium etli cbb₃ oxidase improves drought tolerance of common bean symbiotic nitrogen fixation. J Exp Bot 2012; 63:5035-5043. [PMID: 22511804 DOI: 10.1093/jxb/ers101] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
To investigate the involvement of Rhizobium etli cbb(3) oxidase in the response of Phaseolus vulgaris to drought, common bean plants were inoculated with the R. etli strain, CFNX713, overexpressing this oxidase in bacteroids (cbb(3)(+)) and subjected to drought conditions. The negative effect of drought on plant and nodule dryweight, nitrogen content, and nodule functionality was more pronounced in plants inoculated with the wild-type (WT) strain than in those inoculated with the cbb(3)(+) strain. Regardless of the plant treatment, bacteroids produced by the cbb(3)(+) strain showed higher respiratory capacity than those produced by the WT strain. Inoculation of plants with the cbb(3)(+) strain alleviated the negative effect of a moderate drought on the respiratory capacity of bacteroids and the energy charge of the nodules. Expression of the FixP and FixO components of the cbb(3) oxidase was higher in bacteroids of the cbb(3)(+) strain than in those of the WT strain under all experimental conditions. The decline in sucrose synthase activity and the decrease in dicarboxylic acids provoked by moderate drought stress were more pronounced in nodules from plants inoculated with the WT strain than in those inoculated with the cbb(3)(+) strain. Taken together, these results suggest that inoculation of plants with a R. etli strain having enhanced expression of cbb(3) oxidase in bacteroids reduces the sensitivity of P. vulgaris-R. etli symbiosis to drought and can modulate carbon metabolism in nodules.
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Affiliation(s)
- C Talbi
- Estación Experimental del Zaidin, CSIC, P. O. Box 419, 18080-Granada, Spain
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15
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Asensio AC, Marino D, James EK, Ariz I, Arrese-Igor C, Aparicio-Tejo PM, Arredondo-Peter R, Moran JF. Expression and localization of a Rhizobium-derived cambialistic superoxide dismutase in pea (Pisum sativum) nodules subjected to oxidative stress. Mol Plant Microbe Interact 2011; 24:1247-57. [PMID: 21774575 DOI: 10.1094/mpmi-10-10-0253] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Two phylogenetically unrelated superoxide dismutase (SOD) families, i.e., CuZnSOD (copper and zinc SOD) and FeMn-CamSOD (iron, manganese, or cambialistic SOD), eliminate superoxide radicals in different locations within the plant cell. CuZnSOD are located within the cytosol and plastids, while the second family of SOD, which are considered to be of bacterial origin, are usually located within organelles, such as mitochondria. We have used the reactive oxygen species-producer methylviologen (MV) to study SOD isozymes in the indeterminate nodules on pea (Pisum sativum). MV caused severe effects on nodule physiology and structure and also resulted in an increase in SOD activity. Purification and N-terminal analysis identified CamSOD from the Rhizobium leguminosarum endosymbiont as one of the most active SOD in response to the oxidative stress. Fractionation of cell extracts and immunogold labeling confirmed that the CamSOD was present in both the bacteroids and the cytosol (including the nuclei, plastids, and mitochondria) of the N-fixing cells, and also within the uninfected cortical and interstitial cells. These findings, together with previous reports of the occurrence of FeSOD in determinate nodules, indicate that FeMnCamSOD have specific functions in legumes, some of which may be related to signaling between plant and bacterial symbionts, but the occurrence of one or more particular isozymes depends upon the nodule type.
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Affiliation(s)
- Aaron C Asensio
- Institute of Agro-Biotechnology, IdAB-CSIC-UPNa-GN, Public University of Navarre, Spain
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Sassi S, Aydi S, Gonzalez EM, Arrese-Igor C, Abdelly C. Understanding osmotic stress tolerance in leaves and nodules of two Phaseolus vulgaris cultivars with contrasting drought tolerance. Symbiosis 2010. [DOI: 10.1007/s13199-010-0091-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Larrainzar E, Wienkoop S, Scherling C, Kempa S, Ladrera R, Arrese-Igor C, Weckwerth W, González EM. Carbon metabolism and bacteroid functioning are involved in the regulation of nitrogen fixation in Medicago truncatula under drought and recovery. Mol Plant Microbe Interact 2009; 22:1565-76. [PMID: 19888822 DOI: 10.1094/mpmi-22-12-1565] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Regulation of symbiotic nitrogen fixation (SNF) during drought stress is complex and not yet fully understood. In the present work, the involvement of nodule C and N metabolism in the regulation of SNF in Medicago truncatula under drought and a subsequent rewatering treatment was analyzed using a combination of metabolomic and proteomic approaches. Drought induced a reduction of SNF rates and major changes in the metabolic profile of nodules, mostly an accumulation of amino acids (Pro, His, and Trp) and carbohydrates (sucrose, galactinol, raffinose, and trehalose). This accumulation was coincidental with a decline in the levels of bacteroid proteins involved in SNF and C metabolism, along with a partial reduction of the levels of plant sucrose synthase 1 (SuSy1). In contrast, the variations in enzymes related to N assimilation were found not to correlate with the reduction in SNF, suggesting that these enzymes do not have a role in the regulation of SNF. Unlike the situation in other legumes such as pea and soybean, the drought-induced inhibition of SNF in M. truncatula appears to be caused by impairment of bacteroid metabolism and N(2)-fixing capacity rather than a limitation of respiratory substrate.
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Affiliation(s)
- Estíbaliz Larrainzar
- Departamento Ciencias del Medio Natural, Universidad Pública de Navarra, Pamplona, Spain
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Zabalza A, Gálvez L, Marino D, Royuela M, Arrese-Igor C, González EM. The application of ascorbate or its immediate precursor, galactono-1,4-lactone, does not affect the response of nitrogen-fixing pea nodules to water stress. J Plant Physiol 2008; 165:805-12. [PMID: 17931744 DOI: 10.1016/j.jplph.2007.08.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Revised: 07/31/2007] [Accepted: 08/01/2007] [Indexed: 05/20/2023]
Abstract
Nitrogen fixation in legumes is dramatically inhibited by abiotic stresses, and this reduction is often associated with oxidative damage. Although ascorbate (ASC) has been firmly associated with antioxidant defence, recent studies have suggested that the functions of ASC are related primarily to developmental processes. This study examines the hypothesis that ASC is involved in alleviating the oxidative damage to nodules caused by an increase in reactive oxygen species (ROS) under water stress. The hypothesis was tested by supplying 5mM ASC to pea plants (Pisum sativum L.) experiencing moderate water stress (ca. -1 MPa) and monitoring plant responses in relation to those experiencing the same water stress without ASC. A supply of exogenous ASC increased the nodule ASC+dehydroascorbate (DHA) pool compared to water-stressed nodules without ASC, and significantly modulated the response to water stress of the unspecific guaiacol peroxidase (EC 1.11.1.7) in leaves and nodules. However, ASC supply did not produce recovery from water stress in other nodule antioxidant enzymes, nodule carbon and nitrogen enzymes, or nitrogen fixation. The supply of the immediate ASC precursor, galactono-1,4-lactone (GL), increased the nodule ASC+DHA pool, but also failed to prevent the decline of nitrogen fixation and the reduction of carbon flux in nodules. These results suggest that ASC has a limited role in preventing the negative effects of water stress on nodule metabolism and nitrogen fixation.
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Affiliation(s)
- Ana Zabalza
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus de Arrosadía, E-31006 Pamplona, Spain
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Marino D, Hohnjec N, Küster H, Moran JF, González EM, Arrese-Igor C. Evidence for transcriptional and post-translational regulation of sucrose synthase in pea nodules by the cellular redox state. Mol Plant Microbe Interact 2008; 21:622-30. [PMID: 18393622 DOI: 10.1094/mpmi-21-5-0622] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Nitrogen fixation (NF) in legume nodules is very sensitive to environmental constraints. Nodule sucrose synthase (SS; EC 2.4.1.13) has been suggested to play a crucial role in those circumstances because its downregulation leads to an impaired glycolytic carbon flux and, therefore, a depletion of carbon substrates for bacteroids. In the present study, the likelihood of SS being regulated by oxidative signaling has been addressed by the in vivo supply of paraquat (PQ) to nodulated pea plants and the in vitro effects of oxidizing and reducing agents on nodule SS. PQ produced cellular redox imbalance leading to an inhibition of NF. This was preceded by the downregulation of SS gene expression, protein content, and activity. In vitro, oxidizing agents were able to inhibit SS activity and this inhibition was completely reversed by the addition of dithiothreitol. The overall results are consistent with a regulation model of nodule SS exerted by the cellular redox state at both the transcriptional and post-translational levels. The importance of such mechanisms for the regulation of NF in response to environmental stresses are discussed.
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Affiliation(s)
- Daniel Marino
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, E-31006 Pamplona, Spain
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20
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Wienkoop S, Larrainzar E, Glinski M, González EM, Arrese-Igor C, Weckwerth W. Absolute quantification of Medicago truncatula sucrose synthase isoforms and N-metabolism enzymes in symbiotic root nodules and the detection of novel nodule phosphoproteins by mass spectrometry. J Exp Bot 2008; 59:3307-15. [PMID: 18772307 PMCID: PMC2529246 DOI: 10.1093/jxb/ern182] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2008] [Revised: 06/17/2008] [Accepted: 06/18/2008] [Indexed: 05/20/2023]
Abstract
Mass spectrometry (MS) has become increasingly important for tissue specific protein quantification at the isoform level, as well as for the analysis of protein post-translational regulation mechanisms and turnover rates. Thanks to the development of high accuracy mass spectrometers, peptide sequencing without prior knowledge of the amino acid sequence--de novo sequencing--can be performed. In this work, absolute quantification of a set of key enzymes involved in carbon and nitrogen metabolism in Medicago truncatula 'Jemalong A17' root nodules is presented. Among them, sucrose synthase (SuSy; EC 2.4.1.13), one of the central enzymes in sucrose cleavage in root nodules, has been further characterized and the relative phosphorylation state of the three most abundant isoforms has been quantified. De novo sequencing provided sequence information of a so far unidentified peptide, most probably belonging to SuSy2, the second most abundant isoform in M. truncatula root nodules. TiO(2)-phosphopeptide enrichment led to the identification of not only a phosphorylation site at Ser11 in SuSy1, but also of several novel phosphorylation sites present in other root nodule proteins such as alkaline invertase (AI; EC 3.2.1.26) and an RNA-binding protein.
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Affiliation(s)
- Stefanie Wienkoop
- Institute of Biochemistry and Biology, University of Potsdam, c/o MPI-MP, D-14476 Potsdam, Germany.
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Ladrera R, Marino D, Larrainzar E, González EM, Arrese-Igor C. Reduced carbon availability to bacteroids and elevated ureides in nodules, but not in shoots, are involved in the nitrogen fixation response to early drought in soybean. Plant Physiol 2007; 145:539-46. [PMID: 17720761 PMCID: PMC2048725 DOI: 10.1104/pp.107.102491] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2007] [Accepted: 08/09/2007] [Indexed: 05/16/2023]
Abstract
Nitrogen fixation (NF) in soybean (Glycine max L. Merr.) is highly sensitive to soil drying. This sensitivity has been related to an accumulation of nitrogen compounds, either in shoots or in nodules, and a nodular carbon flux shortage under drought. To assess the relative importance of carbon and nitrogen status on NF regulation, the responses to the early stages of drought were monitored with two soybean cultivars with known contrasting tolerance to drought. In the sensitive cultivar ('Biloxi'), NF inhibition occurred earlier and was more dramatic than in the tolerant cultivar ('Jackson'). The carbon flux to bacteroids was also more affected in 'Biloxi' than in 'Jackson', due to an earlier inhibition of sucrose synthase activity and a larger decrease of malate concentration in the former. Drought provoked ureide accumulation in nodules of both cultivars, but this accumulation was higher and occurred earlier in 'Biloxi'. However, at this early stage of drought, there was no accumulation of ureides in the leaves of either cultivar. These results indicate that a combination of both reduced carbon flux and nitrogen accumulation in nodules, but not in shoots, is involved in the inhibition of NF in soybean under early drought.
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Affiliation(s)
- Rubén Ladrera
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus de Arrosadía, E-31006 Pamplona, Spain
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Larrainzar E, Wienkoop S, Weckwerth W, Ladrera R, Arrese-Igor C, González EM. Medicago truncatula root nodule proteome analysis reveals differential plant and bacteroid responses to drought stress. Plant Physiol 2007; 144:1495-507. [PMID: 17545507 PMCID: PMC1914115 DOI: 10.1104/pp.107.101618] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Drought is one of the environmental factors most affecting crop production. Under drought, symbiotic nitrogen fixation is one of the physiological processes to first show stress responses in nodulated legumes. This inhibition process involves a number of factors whose interactions are not yet understood. This work aims to further understand changes occurring in nodules under drought stress from a proteomic perspective. Drought was imposed on Medicago truncatula 'Jemalong A17' plants grown in symbiosis with Sinorhizobium meliloti strain 2011. Changes at the protein level were analyzed using a nongel approach based on liquid chromatography coupled to tandem mass spectrometry. Due to the complexity of nodule tissue, the separation of plant and bacteroid fractions in M. truncatula root nodules was first checked with the aim of minimizing cross contamination between the fractions. Second, the protein plant fraction of M. truncatula nodules was profiled, leading to the identification of 377 plant proteins, the largest description of the plant nodule proteome so far. Third, both symbiotic partners were independently analyzed for quantitative differences at the protein level during drought stress. Multivariate data mining allowed for the classification of proteins sets that were involved in drought stress responses. The isolation of the nodule plant and bacteroid protein fractions enabled the independent analysis of the response of both counterparts, gaining further understanding of how each symbiotic member is distinctly affected at the protein level under a water-deficit situation.
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Affiliation(s)
- Estíbaliz Larrainzar
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Pamplona, Navarra, Spain
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Naya L, Ladrera R, Ramos J, González EM, Arrese-Igor C, Minchin FR, Becana M. The response of carbon metabolism and antioxidant defenses of alfalfa nodules to drought stress and to the subsequent recovery of plants. Plant Physiol 2007; 144:1104-14. [PMID: 17468213 PMCID: PMC1914205 DOI: 10.1104/pp.107.099648] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2007] [Accepted: 04/13/2007] [Indexed: 05/15/2023]
Abstract
Alfalfa (Medicago sativa) plants were exposed to drought to examine the involvement of carbon metabolism and oxidative stress in the decline of nitrogenase (N(2)ase) activity. Exposure of plants to a moderate drought (leaf water potential of -1.3 MPa) had no effect on sucrose (Suc) synthase (SS) activity, but caused inhibition of N(2)ase activity (-43%), accumulation of succinate (+36%) and Suc (+58%), and up-regulation of genes encoding cytosolic CuZn-superoxide dismutase (SOD), plastid FeSOD, cytosolic glutathione reductase, and bacterial MnSOD and catalases B and C. Intensification of stress (-2.1 MPa) decreased N(2)ase (-82%) and SS (-30%) activities and increased malate (+40%), succinate (+68%), and Suc (+435%). There was also up-regulation (mRNA) of cytosolic ascorbate peroxidase and down-regulation (mRNA) of SS, homoglutathione synthetase, and bacterial catalase A. Drought stress did not affect nifH mRNA level or leghemoglobin expression, but decreased MoFe- and Fe-proteins. Rewatering of plants led to a partial recovery of the activity (75%) and proteins (>64%) of N(2)ase, a complete recovery of Suc, and a decrease of malate (-48%) relative to control. The increase in O(2) diffusion resistance, the decrease in N(2)ase-linked respiration and N(2)ase proteins, the accumulation of respiratory substrates and oxidized lipids and proteins, and the up-regulation of antioxidant genes reveal that bacteroids have their respiratory activity impaired and that oxidative stress occurs in nodules under drought conditions prior to any detectable effect on SS or leghemoglobin. We conclude that a limitation in metabolic capacity of bacteroids and oxidative damage of cellular components are contributing factors to the inhibition of N(2)ase activity in alfalfa nodules.
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Affiliation(s)
- Loreto Naya
- Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas, 50080 Zaragoza, Spain
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Marino D, Frendo P, Ladrera R, Zabalza A, Puppo A, Arrese-Igor C, González EM. Nitrogen fixation control under drought stress. Localized or systemic? Plant Physiol 2007; 143:1968-74. [PMID: 17416644 PMCID: PMC1851803 DOI: 10.1104/pp.106.097139] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Legume-Rhizobium nitrogen fixation is dramatically affected under drought and other environmental constraints. However, it has yet to be established as to whether such regulation of nitrogen fixation is only exerted at the whole-plant level (e.g. by a systemic nitrogen feedback mechanism) or can also occur at a local nodule level. To address this question, nodulated pea (Pisum sativum) plants were grown in a split-root system, which allowed for half of the root system to be irrigated at field capacity, while the other half was water deprived, thus provoking changes in the nodule water potential. Nitrogen fixation only declined in the water-deprived, half-root system and this result was correlated with modifications in the activities of key nodule's enzymes such as sucrose synthase and isocitrate dehydrogenase and in nodular malate content. Furthermore, the decline in nodule water potential resulted in a cell redox imbalance. The results also indicate that systemic nitrogen feedback signaling was not operating in these water-stressed plants, since nitrogen fixation activity was maintained at control values in the watered half of the split-root plants. Thus, the use of a partially droughted split-root system provides evidence that nitrogen fixation activity under drought stress is mainly controlled at the local level rather than by a systemic nitrogen signal.
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Affiliation(s)
- Daniel Marino
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus Arrosadía, 31006 Pamplona, Spain
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25
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Marino D, Frendo P, Ladrera R, Zabalza A, Puppo A, Arrese-Igor C, González EM. Nitrogen fixation control under drought stress. Localized or systemic? Plant Physiol 2007. [PMID: 17416644 DOI: 10.1104/pp.107.097139] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Legume-Rhizobium nitrogen fixation is dramatically affected under drought and other environmental constraints. However, it has yet to be established as to whether such regulation of nitrogen fixation is only exerted at the whole-plant level (e.g. by a systemic nitrogen feedback mechanism) or can also occur at a local nodule level. To address this question, nodulated pea (Pisum sativum) plants were grown in a split-root system, which allowed for half of the root system to be irrigated at field capacity, while the other half was water deprived, thus provoking changes in the nodule water potential. Nitrogen fixation only declined in the water-deprived, half-root system and this result was correlated with modifications in the activities of key nodule's enzymes such as sucrose synthase and isocitrate dehydrogenase and in nodular malate content. Furthermore, the decline in nodule water potential resulted in a cell redox imbalance. The results also indicate that systemic nitrogen feedback signaling was not operating in these water-stressed plants, since nitrogen fixation activity was maintained at control values in the watered half of the split-root plants. Thus, the use of a partially droughted split-root system provides evidence that nitrogen fixation activity under drought stress is mainly controlled at the local level rather than by a systemic nitrogen signal.
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Affiliation(s)
- Daniel Marino
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus Arrosadía, 31006 Pamplona, Spain
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Marino D, González EM, Frendo P, Puppo A, Arrese-Igor C. NADPH recycling systems in oxidative stressed pea nodules: a key role for the NADP+ -dependent isocitrate dehydrogenase. Planta 2007; 225:413-21. [PMID: 16896792 DOI: 10.1007/s00425-006-0354-5] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Accepted: 06/22/2006] [Indexed: 05/11/2023]
Abstract
The symbiosis between legumes and rhizobia is characterised by the formation of dinitrogen-fixing root nodules. In natural conditions, nitrogen fixation is strongly impaired by abiotic stresses which generate over-production of reactive oxygen species. Since one of the nodule main antioxidant systems is the ascorbate-glutathione cycle, NADPH recycling that is involved in glutathione reduction is of great relevance under stress conditions. NADPH is mainly produced by glucose 6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44) from the oxidative pentose phosphate pathway, and also by NADP(+)-dependent isocitrate dehydrogenase (ICDH; EC 1.1.1.42). In this work, 10 microM paraquat (PQ) was applied to pea roots in order to determine the in vivo relationship between oxidative stress and the activity of the NADPH-generating enzymes in nodules. Whereas G6PDH and 6PGDH activities remained unchanged, a remarkable induction of ICDH gene expression and a dramatic increase of the ICDH activity was observed during the PQ treatment. These results support that ICDH has a key role in NADPH recycling under oxidative stress conditions in pea root nodules.
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Affiliation(s)
- Daniel Marino
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus Arrosadía, 31006, Pamplona, Spain
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Marino D, González EM, Arrese-Igor C. Drought effects on carbon and nitrogen metabolism of pea nodules can be mimicked by paraquat: evidence for the occurrence of two regulation pathways under oxidative stresses. J Exp Bot 2006; 57:665-73. [PMID: 16415332 DOI: 10.1093/jxb/erj056] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Biological nitrogen fixation (BNF) is dramatically affected by environmental constraints such as water stress or heavy metals. It has been reported that these stresses induce the over-production of reactive oxygen species (ROS) and, in turn, oxidative stress that may be responsible for the above-mentioned BNF decline at the molecular level. Oxidative stress, occurring under different environmental stresses, has been widely related to physiological damage. However, a direct relationship between oxidative stress and the decline of BNF, independently from any other cellular damage resulting from adverse environmental situations, has yet to be demonstrated. In order to study the likely in vivo relationship between ROS and BNF inhibition in the legume-Rhizobium symbiosis, two paraquat (PQ) doses, 1 (LPQ) and 10 (HPQ) mmol m(-3), were applied to pea roots for 96 h in order to exacerbate ROS production. Whole-plant physiology and nodule metabolism parameters were determined every 24 h to monitor the evolution of plant responses to ROS. LPQ provoked BNF decline, which was preceded by a prior decrease in sucrose synthase (SS) activity. However, HPQ gave rise to a faster and more pronounced BNF inhibition, which coincided with a decline in SS and also with a reduction in leghaemoglobin (Lb) content. These results indicate a likely involvement of ROS in the effects of environmental stresses on BNF. Furthermore, these results support the occurrence of two regulation pathways for BNF under oxidative stress, one of these involving carbon shortage and the other involving Lb/oxygen flux.
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Affiliation(s)
- Daniel Marino
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus de Arrosadía, E-31006 Pamplona, Spain
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Zabalza A, González EM, Arrese-Igor C, Royuela M. Fermentative metabolism is induced by inhibiting different enzymes of the branched-chain amino acid biosynthesis pathway in pea plants. J Agric Food Chem 2005; 53:7486-93. [PMID: 16159177 DOI: 10.1021/jf050654x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The inhibition of branched-chain amino acid (BCAA) biosynthesis was evaluated in pea plants in relation to the ability for induction of fermentative metabolism under aerobic conditions. Chlorsulfuron and imazethapyr (inhibitors of acetolactate synthase, ALS, EC 4.1.3.18) produced a strong induction of pyruvate decarboxylase (PDC, EC 4.1.1.1) and alcohol dehydrogenase (ADH, EC 1.1.1.1) activities and a lesser induction of lactate dehydrogenase (LDH, EC 1.1.1.27) and alanine aminotransferase (AlaAT, EC 2.6.1.2) activities in roots. Inhibition of the second enzyme of the BCAA biosynthesis (ketol-acid reductoisomerase, KARI, EC 1.1.1.86) by Hoe 704 (2-dimethylphosphinoyl-2-hydroxyacetic acid) and CPCA (1,1-cyclopropanedicarboxylic acid) enhanced fermentative enzyme activities including PDC, ADH, and AlaAT. Fermentative metabolism induction occurring with ALS- and KARI-inhibitors was related to a higher expression of PDC. In the case of KARI inhibition, it is proposed that fermentation induction is due to an inhibition of ALS activity resulted from an increase in acetolactate concentration. Fermentative metabolism induction in roots, or at least ethanolic fermentation, appeared to be a general physiological response to the BCAA biosynthesis inhibition.
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Affiliation(s)
- Ana Zabalza
- Departamento Ciencias del Medio Natural, Universidad Pública de Navarra, Campus Arrosadia, Pamplona, Spain
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Gálvez L, González EM, Arrese-Igor C. Evidence for carbon flux shortage and strong carbon/nitrogen interactions in pea nodules at early stages of water stress. J Exp Bot 2005; 56:2551-61. [PMID: 16061503 DOI: 10.1093/jxb/eri249] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Symbiotic N2 fixation in legume nodules declines under a wide range of environmental stresses. A high correlation between N2 fixation decline and sucrose synthase (SS; EC 2.4.1.13) activity down-regulation has been reported, although it has still to be elucidated whether a causal relationship between SS activity down-regulation and N2 fixation decline can be established. In order to study the likely C/N interactions within nodules and the effects on N2 fixation, pea plants (Pisum sativum L. cv. Sugar snap) were subjected to progressive water stress by withholding irrigation. Under these conditions, nodule SS activity declined concomitantly with apparent nitrogenase activity. The levels of UDP-glucose, glucose-1-phosphate, glucose-6-phosphate, and fructose-6-phosphate decreased in water-stressed nodules compared with unstressed nodules. Drought also had a marked effect on nodule concentrations of malate, succinate, and alpha-ketoglutarate. Moreover, a general decline in nodule adenylate content was detected. NADP+-dependent isocitrate dehydrogenase (ICDH; EC 1.1.1.42) was the only enzyme whose activity increased as a result of water deficit, compensating for a possible C/N imbalance and/or supplying NADPH in circumstances that the pentose phosphate pathway was impaired, as suggested by the decline in glucose-6-phosphate dehydrogenase (G6PDH; EC 1.1.1.49) activity. The overall results show the occurrence of strong C/N interactions in nodules subjected to water stress and support a likely limitation of carbon flux that might be involved in the decline of N2 fixation under drought.
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Affiliation(s)
- Loli Gálvez
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus de Arrosadía, E-31006 Pamplona, Spain
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Rubio MC, González EM, Minchin FR, Webb KJ, Arrese-Igor C, Ramos J, Becana M. Effects of water stress on antioxidant enzymes of leaves and nodules of transgenic alfalfa overexpressing superoxide dismutases. Physiol Plant 2002; 115:531-540. [PMID: 12121459 DOI: 10.1034/j.1399-3054.2002.1150407.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The antioxidant composition and relative water stress tolerance of nodulated alfalfa plants (Medicago sativa L. x Sinorhizobium meliloti 102F78) of the elite genotype N4 and three derived transgenic lines have been studied in detail. These transgenic lines overproduced, respectively, Mn-containing superoxide dismutase (SOD) in the mitochondria of leaves and nodules, MnSOD in the chloroplasts, and FeSOD in the chloroplasts. In general for all lines, water stress caused moderate decreases in MnSOD and FeSOD activities in both leaves and nodules, but had distinct tissue-dependent effects on the activities of the peroxide-scavenging enzymes. During water stress, with a few exceptions, ascorbate peroxidase and catalase activities increased moderately in leaves but decreased in nodules. At mild water stress, transgenic lines showed, on average, 20% higher photosynthetic activity than the parental line, which suggests a superior tolerance of transgenic plants under these conditions. However, the untransformed and the transgenic plants performed similarly during moderate and severe water stress and recovery with respect to important markers of metabolic activity and of oxidative stress in leaves and nodules. We conclude that the base genotype used for transformation and the background SOD isozymic composition may have a profound effect on the relative tolerance of the transgenic lines to abiotic stress.
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Affiliation(s)
- Maria C Rubio
- Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas, Apdo 202,E-50080 Zaragoza, Spain Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, E-31006 Pamplona, Spain Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, SY23 3EB, UK
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Gaston S, Zabalza A, González EM, Arrese-Igor C, Aparicio-Tejo PM, Royuela M. Imazethapyr, an inhibitor of the branched-chain amino acid biosynthesis, induces aerobic fermentation in pea plants. Physiol Plant 2002; 114:524-532. [PMID: 11975725 DOI: 10.1034/j.1399-3054.2002.1140404.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Acetolactate synthase (ALS; EC 4.1.3.18) inhibition is the primary mechanism of action of imazethapyr (IM). However, the precise mechanisms that links ALS inhibition with plant death have not been elucidated. Supply of IM to pea (Pisum sativum L) plants produced an immediate cessation of growth, caused a 50% inhibition of the in vivo ALS activity within 1 day of treatment, and a remarkable accumulation (2.7-times) of free amino acids after 3 days. Carbohydrates (soluble and starch) were accumulated in both leaves and roots. Accumulation of soluble sugars in roots preceded that of starch in leaves, suggesting that the accumulation of carbohydrates in leaves is not the reason for the arrested root growth. A transient pyruvate accumulation was observed in roots, 1 day after the onset of IM supply. This was coincident with an increase in pyruvate decarboxylase (EC 4.1.1.1), and later increases in alcohol dehydrogenase (EC 1.1.1.1), lactate dehydrogenase (EC 1.1.1.27), and alanine amino transferase (EC 2.6.1.2) activities. This enhancement of fermentative activities was coincident with a slight decrease in aerobic respiration. The overall data suggest that the impairment of ALS activity may lead to a fermentative metabolism that may be involved in growth inhibition and plant death.
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Affiliation(s)
- Susana Gaston
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus Arrosadía, E-31006 Pamplona, Spain
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Rubio MC, Ramos J, Webb KJ, Minchin FR, González E, Arrese-Igor C, Becana M. Expression studies of superoxide dismutases in nodules and leaves of transgenic alfalfa reveal abundance of iron-containing isozymes, posttranslational regulation, and compensation of isozyme activities. Mol Plant Microbe Interact 2001; 14:1178-1188. [PMID: 11605957 DOI: 10.1094/mpmi.2001.14.10.1178] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The composition of antioxidant enzymes, especially superoxide dismutase (SOD), was studied in one nontransgenic and three transgenic lines of nodulated alfalfa plants. Transgenic lines overproduced MnSOD in the mitochondria of nodules and leaves (line 1-10), MnSOD in the chloroplasts (line 4-6), and FeSOD in the chloroplasts (line 10-7). In nodules of line 10-7, the absence of transgene-encoded FeSOD activity was due to a lack of mRNA, whereas in nodules of line 4-6 the absence of transgene-encoded MnSOD activity was due to enzyme inactivation or degradation. Transgenic alfalfa showed a novel compensatory effect in the activities of MnSOD (mitochondrial) and FeSOD (plastidic) in the leaves, which was not caused by changes in the mRNA levels. These findings imply that SOD activity in plant tissues and organelles is regulated, at least partially, at the posttranslational level. All four lines had low CuZnSOD activities and an abundant FeSOD isozyme, especially in nodules, indicating that FeSOD performs important antioxidant functions other than the scavenging of superoxide radicals generated in photosynthesis. This was confirmed by the detection of FeSOD cDNAs and proteins in nodules of other legumes such as cowpea, pea, and soybean. The cDNA encoding alfalfa nodule FeSOD was characterized and the deduced protein found to contain a plastid transit peptide. A comparison of sequences and other properties reveals that there are two types of FeSODs in nodules.
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Affiliation(s)
- M C Rubio
- Departamento de Nutrición Vegetal, Estación Experimental de Aula Dei, Consejo Superior de Investigaciones Científicas, Zaragoza, Spain
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González EM, Gálvez L, Royuela M, Aparicio-Tejo PM, Arrese-Igor C. Insights into the regulation of nitrogen fixation in pea nodules: lessons from drought, abscisic acid and increased photoassimilate availability. ACTA ACUST UNITED AC 2001. [DOI: 10.1051/agro:2001151] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Abstract
The recessive gene af produces a modification of Pisum sativum L. leaf morphology, where leaflets are replaced by tendrils. Previous reports have suggested that tendrils may contribute to plant growth in a similar way to flat leaf structures, but these reports have been restricted to carbon metabolism. In this work, we investigate the nitrate reduction (nitrate reductase activity) capacity of tendrils of a semi-leafless variety, Solara, in relation to other leaf structures. Maximum nitrate reductase activity (EC 1.6.6.1), expressed on a protein basis, was significantly lower in tendrils compared to flat structures. However, the activation state of nitrate reductase was significantly higher in tendrils, reaching 70%, compared to flat leaf structures. According to these results, tendrils contributed up to 25% of the overall plant nitrate reduction in the semi-leafless variety. This figure was even higher when nitrate reduction was calculated from in vivo measurements. The results are discussed in relation to nitrate, magnesium, carbohydrates, amino acids and adenylate levels of tendrils.
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Affiliation(s)
- Esther M. González
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus Arrosadía, E-31006 Pamplona, Spain
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González EM, Gálvez L, Arrese-Igor C. Abscisic acid induces a decline in nitrogen fixation that involves leghaemoglobin, but is independent of sucrose synthase activity. J Exp Bot 2001; 52:285-93. [PMID: 11283173 DOI: 10.1093/jexbot/52.355.285] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Sucrose synthase (SS) activity has been suggested to be a key point of regulation in nodule metabolism since this enzyme is down-regulated in response to different stresses which lead to decreased nitrogen fixation. In soybean, a dramatic decline of SS transcripts has been observed within 1 d from the onset of drought. Such a quick response suggests mediation by a signal transduction molecule. Abscisic acid (ABA) is a likely candidate to act as such a molecule as it mediates in a significant number of plant responses to environmental constraints. The hypothesis of ABA controlling nodule metabolism was approached in this work by assessing nodule responses to exogenous ABA supply in pea. Under the experimental conditions, ABA did not affect plant biomass, nodule numbers or dry weight. However, nitrogen fixation rate was reduced by 70% within 5 d and by 80% after 9 d leading to a reduced plant organic nitrogen content. Leghaemoglobin (Lb) content declined in parallel with that of nitrogen fixation. SS activity, however, was not affected by ABA treatment, and neither were the activities of the enzymes aspartate amino transferase, alkaline invertase, malate dehydrogenase, glutamate synthase, uridine diphosphoglucose pyrophosphorylase, isocitrate dehydrogenase, and glutamine synthetase. Nodule bacteroid-soluble protein content was reduced in nodules only after 9 d of ABA treatment. These results do not support the hypothesis that ABA directly regulates SS activity. However, they do suggest the occurrence of at least two different control pathways in nodules under environmental constraints, which include ABA being involved in a Lb/oxygen-related control of nitrogen fixation.
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Affiliation(s)
- E M González
- Departamento de Ciencias del Medio Natural, Universidad Pública de Navarra, Campus de Arrosadía, E-31006 Pamplona, Spain
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Royuela M, Gonzalez A, Arrese-Igor C, Aparicio-Tejo PM, Gonzalez-Murua C. Imazethapyr inhibition of acetolactate synthase inRhizobiumand its symbiosis with pea. ACTA ACUST UNITED AC 1999. [DOI: 10.1002/(sici)1096-9063(199804)52:4<372::aid-ps730>3.0.co;2-p] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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