International Journal of Molecular Sciences

Editorial

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Open AccessEditorial

Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms

by Saad Sulieman and Lam-Son Phan Tran

Int. J. Mol. Sci. 2014, 15(11), 19389-19393; https://doi.org/10.3390/ijms151119389 - 24 Oct 2014

Cited by 27 | Viewed by 7381

Abstract

The special issue “Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms” aims to investigate the physiological and biochemical advances in the symbiotic process with an emphasis on nodule establishment, development and functioning. The original research articles included in this issue provide [...] Read more.

The special issue “Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms” aims to investigate the physiological and biochemical advances in the symbiotic process with an emphasis on nodule establishment, development and functioning. The original research articles included in this issue provide important information regarding novel aspects of nodule metabolism and various regulatory pathways, which could have important future implications. This issue also included one review article that highlights the importance of using legume trees in the production of renewable biofuels. Full article

(This article belongs to the Special Issue Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms)

Research

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1385 KiB

Open AccessArticle

Identification of Cold-Responsive miRNAs and Their Target Genes in Nitrogen-Fixing Nodules of Soybean

by Senlei Zhang, Youning Wang, Kexue Li, Yanmin Zou, Liang Chen and Xia Li

Int. J. Mol. Sci. 2014, 15(8), 13596-13614; https://doi.org/10.3390/ijms150813596 - 5 Aug 2014

Cited by 49 | Viewed by 8775

Abstract

As a warm climate species, soybean is highly sensitive to chilling temperatures. Exposure to chilling temperatures causes a significant reduction in the nitrogen fixation rate in soybean plants and subsequent yield loss. However, the molecular basis for the sensitivity of soybean to chilling [...] Read more.

As a warm climate species, soybean is highly sensitive to chilling temperatures. Exposure to chilling temperatures causes a significant reduction in the nitrogen fixation rate in soybean plants and subsequent yield loss. However, the molecular basis for the sensitivity of soybean to chilling is poorly understood. In this study, we identified cold-responsive miRNAs in nitrogen-fixing nodules of soybean. Upon chilling, the expression of gma-miR397a, gma-miR166u and gma-miR171p was greatly upregulated, whereas the expression of gma-miR169c, gma-miR159b, gma-miR319a/b and gma-miR5559 was significantly decreased. The target genes of these miRNAs were predicted and validated using 5' complementary DNA ends (5'-RACE) experiments, and qPCR analysis identified putative genes targeted by the cold-responsive miRNAs in response to chilling temperatures. Taken together, our results reveal that miRNAs may be involved in the protective mechanism against chilling injury in mature nodules of soybean. Full article

(This article belongs to the Special Issue Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms)

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348 KiB

Open AccessArticle

The Activity of Nodules of the Supernodulating Mutant Mt_sunn Is not Limited by Photosynthesis under Optimal Growth Conditions

by Ricardo A. Cabeza, Annika Lingner, Rebecca Liese, Saad Sulieman, Mehmet Senbayram, Merle Tränkner, Klaus Dittert and Joachim Schulze

Int. J. Mol. Sci. 2014, 15(4), 6031-6045; https://doi.org/10.3390/ijms15046031 - 10 Apr 2014

Cited by 13 | Viewed by 8419

Abstract

Legumes match the nodule number to the N demand of the plant. When a mutation in the regulatory mechanism deprives the plant of that ability, an excessive number of nodules are formed. These mutants show low productivity in the fields, mainly due to [...] Read more.

Legumes match the nodule number to the N demand of the plant. When a mutation in the regulatory mechanism deprives the plant of that ability, an excessive number of nodules are formed. These mutants show low productivity in the fields, mainly due to the high carbon burden caused through the necessity to supply numerous nodules. The objective of this study was to clarify whether through optimal conditions for growth and CO₂ assimilation a higher nodule activity of a supernodulating mutant of Medicago truncatula (M. truncatula) can be induced. Several experimental approaches reveal that under the conditions of our experiments, the nitrogen fixation of the supernodulating mutant, designated as sunn (super numeric nodules), was not limited by photosynthesis. Higher specific nitrogen fixation activity could not be induced through short- or long-term increases in CO₂ assimilation around shoots. Furthermore, a whole plant P depletion induced a decline in nitrogen fixation, however this decline did not occur significantly earlier in sunn plants, nor was it more intense compared to the wild-type. However, a distinctly different pattern of nitrogen fixation during the day/night cycles of the experiment indicates that the control of N₂ fixing activity of the large number of nodules is an additional problem for the productivity of supernodulating mutants. Full article

(This article belongs to the Special Issue Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms)

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1354 KiB

Open AccessArticle

Effect of Nitrate on Nodule and Root Growth of Soybean (Glycine max (L.) Merr.)

by Akinori Saito, Sayuri Tanabata, Takanari Tanabata, Seiya Tajima, Manabu Ueno, Shinji Ishikawa, Norikuni Ohtake, Kuni Sueyoshi and Takuji Ohyama

Int. J. Mol. Sci. 2014, 15(3), 4464-4480; https://doi.org/10.3390/ijms15034464 - 13 Mar 2014

Cited by 84 | Viewed by 9640

Abstract

The application of combined nitrogen, especially nitrate, to soybean plants is known to strongly inhibit nodule formation, growth and nitrogen fixation. In the present study, we measured the effects of supplying 5 mM nitrate on the growth of nodules, primary root, and lateral [...] Read more.

The application of combined nitrogen, especially nitrate, to soybean plants is known to strongly inhibit nodule formation, growth and nitrogen fixation. In the present study, we measured the effects of supplying 5 mM nitrate on the growth of nodules, primary root, and lateral roots under light at 28 °C or dark at 18 °C conditions. Photographs of the nodulated roots were periodically taken by a digital camera at 1-h intervals, and the size of the nodules was measured with newly developed computer software. Nodule growth was depressed approximately 7 h after the addition of nitrate under light conditions. The nodule growth rate under dark conditions was almost half that under light conditions, and nodule growth was further suppressed by the addition of 5 mM nitrate. Similar results were observed for the extending growth rate of the primary root as those for nodule growth supplied with 5 mM nitrate under light/dark conditions. In contrast, the growth of lateral roots was promoted by the addition of 5 mM nitrate. The 2D-PAGE profiles of nodule protein showed similar patterns between the 0 and 5 mM nitrate treatments, which suggested that metabolic integrity may be maintained with the 5 mM nitrate treatment. Further studies are required to confirm whether light or temperature condition may give the primary effect on the growth of nodules and roots. Full article

(This article belongs to the Special Issue Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms)

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Open AccessCommunication

A Proteomic Approach of Bradyrhizobium/Aeschynomene Root and Stem Symbioses Reveals the Importance of the fixA Locus for Symbiosis

by Nathanael Delmotte, Samuel Mondy, Benoit Alunni, Joel Fardoux, Clémence Chaintreuil, Julia A. Vorholt, Eric Giraud and Benjamin Gourion

Int. J. Mol. Sci. 2014, 15(3), 3660-3670; https://doi.org/10.3390/ijms15033660 - 28 Feb 2014

Cited by 13 | Viewed by 8228

Abstract

Rhizobia are soil bacteria that are able to form symbiosis with plant hosts of the legume family. These associations result in the formation of organs, called nodules in which bacteria fix atmospheric nitrogen to the benefit of the plant. Most of our knowledge [...] Read more.

Rhizobia are soil bacteria that are able to form symbiosis with plant hosts of the legume family. These associations result in the formation of organs, called nodules in which bacteria fix atmospheric nitrogen to the benefit of the plant. Most of our knowledge on the metabolism and the physiology of the bacteria during symbiosis derives from studying roots nodules of terrestrial plants. Here we used a proteomics approach to investigate the bacterial physiology of photosynthetic Bradyrhizobium sp. ORS278 during the symbiotic process with the semi aquatical plant Aeschynomene indica that forms root and stem nodules. We analyzed the proteomes of bacteria extracted from each type of nodule. First, we analyzed the bacteroid proteome at two different time points and found only minor variation between the bacterial proteomes of 2-week- and 3-week-old nodules. High conservation of the bacteroid proteome was also found when comparing stem nodules and root nodules. Among the stem nodule specific proteins were those related to the phototrophic ability of Bradyrhizobium sp. ORS278. Furthermore, we compared our data with those obtained during an extensive genetic screen previously published. The symbiotic role of four candidate genes which corresponding proteins were found massively produced in the nodules but not identified during this screening was examined. Mutant analysis suggested that in addition to the EtfAB system, the fixA locus is required for symbiotic efficiency. Full article

(This article belongs to the Special Issue Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms)

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360 KiB

Open AccessArticle

Plant Dependence on Rhizobia for Nitrogen Influences Induced Plant Defenses and Herbivore Performance

by Jennifer M. Dean, Mark C. Mescher and Consuelo M. De Moraes

Int. J. Mol. Sci. 2014, 15(1), 1466-1480; https://doi.org/10.3390/ijms15011466 - 21 Jan 2014

Cited by 48 | Viewed by 8025

Abstract

Symbiotic rhizobia induce many changes in legumes that could affect aboveground interactions with herbivores. We explored how changing the intensity of Bradyrhizobium japonicum, as modulated by soil nitrogen (N) levels, influenced the interaction between soybean (Glycine max) and herbivores of [...] Read more.

Symbiotic rhizobia induce many changes in legumes that could affect aboveground interactions with herbivores. We explored how changing the intensity of Bradyrhizobium japonicum, as modulated by soil nitrogen (N) levels, influenced the interaction between soybean (Glycine max) and herbivores of different feeding guilds. When we employed a range of fertilizer applications to manipulate soil N, plants primarily dependent on rhizobia for N exhibited increased root nodulation and higher levels of foliar ureides than plants given N fertilizer; yet all treatments maintained similar total N levels. Soybean podworm (Helicoverpa zea) larvae grew best on plants with the highest levels of rhizobia but, somewhat surprisingly, preferred to feed on high-N-fertilized plants when given a choice. Induction of the defense signaling compound jasmonic acid (JA) by H. zea feeding damage was highest in plants primarily dependent on rhizobia. Differences in rhizobial dependency on soybean did not appear to affect interactions with the phloem-feeding soybean aphid (Aphis glycines). Overall, our results suggest that rhizobia association can affect plant nutritional quality and the induction of defense signaling pathways and that these effects may influence herbivore feeding preferences and performance—though such effects may vary considerably for different classes of herbivores. Full article

(This article belongs to the Special Issue Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms)

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917 KiB

Open AccessArticle

Mutation in the pssA Gene Involved in Exopolysaccharide Synthesis Leads to Several Physiological and Symbiotic Defects in Rhizobium leguminosarum bv. trifolii

by Monika Janczarek and Kamila Rachwał

Int. J. Mol. Sci. 2013, 14(12), 23711-23735; https://doi.org/10.3390/ijms141223711 - 5 Dec 2013

Cited by 23 | Viewed by 7845

Abstract

The symbiotic nitrogen-fixing bacterium Rhizobium leguminosarum bv. trifolii 24.2 secretes large amounts of acidic exopolysaccharide (EPS), which plays a crucial role in establishment of effective symbiosis with clover. The biosynthesis of this heteropolymer is conducted by a multi-enzymatic complex located in the bacterial [...] Read more.

The symbiotic nitrogen-fixing bacterium Rhizobium leguminosarum bv. trifolii 24.2 secretes large amounts of acidic exopolysaccharide (EPS), which plays a crucial role in establishment of effective symbiosis with clover. The biosynthesis of this heteropolymer is conducted by a multi-enzymatic complex located in the bacterial inner membrane. PssA protein, responsible for the addition of glucose-1-phosphate to a polyprenyl phosphate carrier, is involved in the first step of EPS synthesis. In this work, we characterize R. leguminosarum bv. trifolii strain Rt270 containing a mini-Tn5 transposon insertion located in the 3'-end of the pssA gene. It has been established that a mutation in this gene causes a pleiotropic effect in rhizobial cells. This is confirmed by the phenotype of the mutant strain Rt270, which exhibits several physiological and symbiotic defects such as a deficiency in EPS synthesis, decreased motility and utilization of some nutrients, decreased sensitivity to several antibiotics, an altered extracellular protein profile, and failed host plant infection. The data of this study indicate that the protein product of the pssA gene is not only involved in EPS synthesis, but also required for proper functioning of Rhizobium leguminosarum bv. trifolii cells. Full article

(This article belongs to the Special Issue Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms)

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Review

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Open AccessReview

The Role of Symbiotic Nitrogen Fixation in Sustainable Production of Biofuels

by Bandana Biswas and Peter M. Gresshoff

Int. J. Mol. Sci. 2014, 15(5), 7380-7397; https://doi.org/10.3390/ijms15057380 - 29 Apr 2014

Cited by 65 | Viewed by 12846

Abstract

With the ever-increasing population of the world (expected to reach 9.6 billion by 2050), and altered life style, comes an increased demand for food, fuel and fiber. However, scarcity of land, water and energy accompanied by climate change means that to produce enough [...] Read more.

With the ever-increasing population of the world (expected to reach 9.6 billion by 2050), and altered life style, comes an increased demand for food, fuel and fiber. However, scarcity of land, water and energy accompanied by climate change means that to produce enough to meet the demands is getting increasingly challenging. Today we must use every avenue from science and technology available to address these challenges. The natural process of symbiotic nitrogen fixation, whereby plants such as legumes fix atmospheric nitrogen gas to ammonia, usable by plants can have a substantial impact as it is found in nature, has low environmental and economic costs and is broadly established. Here we look at the importance of symbiotic nitrogen fixation in the production of biofuel feedstocks; how this process can address major challenges, how improving nitrogen fixation is essential, and what we can do about it. Full article

(This article belongs to the Special Issue Symbiotic Nitrogen Fixation in Legume Nodules: Metabolism and Regulatory Mechanisms)

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