scholarly journals Testing Whether Pre-Pod-Fill Symbiotic Nitrogen Fixation in Soybean Is Subject to Drift or Selection Over 100 Years of Soybean Breeding

2021 ◽  
Vol 3 ◽  
Author(s):  
Malinda S. Thilakarathna ◽  
Davoud Torkamaneh ◽  
Robert W. Bruce ◽  
Istvan Rajcan ◽  
Godfrey Chu ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Symbiotic Nitrogen Fixation ◽  
Root Nodules ◽  
Field Trials ◽  
Direct Selection ◽  
Oilseed Crop ◽  
Fixed Nitrogen ◽  
Soybean Breeding ◽  
Soybean Cultivars ◽  
The Impact

Soybean [Glycine max (L.) Merr.] is the world's leading legume crop and the largest oilseed crop. It forms a symbiotic relationship with rhizobia bacteria residing in root nodules that provide fixed nitrogen to host plants through symbiotic nitrogen fixation (SNF). In soybean, it has been widely reported that the highest SNF occurs at the pod-filling stage, associated with the peak demand for nitrogen. However, the majority of seed nitrogen is derived from remobilizing root/shoot nitrogen, representing cumulative SNF from the seedling stage to the pre-pod-fill stage. Therefore, the question arises as to whether there has also been selection for improved SNF at these earlier stages, or whether pre-pod-fill SNF traits have drifted. To test this hypothesis, in this study, pre-pod SNF-related traits were evaluated in soybean cultivars that span 100 years of breeding selection in the Canadian Province of Ontario. Specifically, we evaluated SNF traits in 19 pedigree-related historical cultivars and 25 modern cultivars derived from the University of Guelph soybean breeding program. Field trials were conducted at Woodstock, Ontario, Canada in 2016 and 2017, and various SNF-related traits were measured at pre-pod-fill stages (R1-R3), including nitrogen fixation capacity. Considerable variation was observed among Canadian soybean cultivars released over the past 100 years for pre-pod-fill nitrogen fixation. The modern soybean cultivars had similar or moderately higher pre-pod-fill SNF compared to the historical lines in terms of the percentage of nitrogen derived from the atmosphere (%Ndfa) and total shoot fixed nitrogen. These findings suggest that, despite no direct selection by breeders, pre-pod-fill nitrogen fixation, and associated SNF traits have been maintained and possibly improved in modern soybean breeding. However, the low level of pre-pod-fill SNF in some modern cultivars, and generally wide variation observed in SNF between them, suggest some level of genetic drift for this trait in some pedigrees. Specific historical and modern soybean cultivars were identified as potential parents to enable targeted breeding for improved pre-pod-fill SNF. This retrospective study sheds light on our understanding of the impact of decades of recent selective breeding on pre-pod-fill nitrogen fixation traits in soybean in a temperate environment.

scholarly journals The rhizobial autotransporter determines the symbiotic nitrogen fixation activity of Lotus japonicus in a host-specific manner

2020 ◽  
Vol 117 (3) ◽  
pp. 1806-1815 ◽  
Author(s):  
Yoshikazu Shimoda ◽  
Yuki Nishigaya ◽  
Hiroko Yamaya-Ito ◽  
Noritoshi Inagaki ◽  
Yosuke Umehara ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Host Plant ◽  
Symbiotic Nitrogen Fixation ◽  
Root Nodules ◽  
Lotus Japonicus ◽  
Dependent Manner ◽  
Strain Specificity ◽  
Passenger Domain ◽  
Aspartic Peptidase ◽  
Specific Manner

Leguminous plants establish endosymbiotic associations with rhizobia and form root nodules in which the rhizobia fix atmospheric nitrogen. The host plant and intracellular rhizobia strictly control this symbiotic nitrogen fixation. We recently reported a Lotus japonicus Fix− mutant, apn1 (aspartic peptidase nodule-induced 1), that impairs symbiotic nitrogen fixation. APN1 encodes a nodule-specific aspartic peptidase involved in the Fix− phenotype in a rhizobial strain-specific manner. This host-strain specificity implies that some molecular interactions between host plant APN1 and rhizobial factors are required, although the biological function of APN1 in nodules and the mechanisms governing the interactions are unknown. To clarify how rhizobial factors are involved in strain-specific nitrogen fixation, we explored transposon mutants of Mesorhizobium loti strain TONO, which normally form Fix− nodules on apn1 roots, and identified TONO mutants that formed Fix+ nodules on apn1. The identified causal gene encodes an autotransporter, part of a protein secretion system of Gram-negative bacteria. Expression of the autotransporter gene in M. loti strain MAFF3030399, which normally forms Fix+ nodules on apn1 roots, resulted in Fix− nodules. The autotransporter of TONO functions to secrete a part of its own protein (a passenger domain) into extracellular spaces, and the recombinant APN1 protein cleaved the passenger protein in vitro. The M. loti autotransporter showed the activity to induce the genes involved in nodule senescence in a dose-dependent manner. Therefore, we conclude that the nodule-specific aspartic peptidase, APN1, suppresses negative effects of the rhizobial autotransporter in order to maintain effective symbiotic nitrogen fixation in root nodules.

Effect of plant genotype and nitrogen fertilizer on symbiotic nitrogen fixation by soybean cultivars

1984 ◽  
Vol 82 (3) ◽  
pp. 397-405 ◽  
Author(s):  
G. Hardarson ◽  
F. Zapata ◽  
S. K. A. Danso
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogen Fertilizer ◽  
Symbiotic Nitrogen Fixation ◽  
Plant Genotype ◽  
Soybean Cultivars

Détermination de l'identité isotopique de l'azote fixé par le Frankia associé au genre Alnus

1988 ◽  
Vol 66 (7) ◽  
pp. 1241-1247 ◽  
Author(s):  
A. M. Domenach ◽  
F. Kurdali ◽  
C. Danière ◽  
R. Bardin
Keyword(s):  
Nitrogen Fixation ◽  
Symbiotic Nitrogen Fixation ◽  
Alnus Glutinosa ◽  
Natural Ecosystem ◽  
Free Medium ◽  
Fixed Nitrogen ◽  
Aerial Parts ◽  
Reference Plant ◽  
N Enrichment ◽  
N Natural Abundance

To use the 15N natural abundance method to evaluate the symbiotic nitrogen fixation by actinorhizal trees, it is necessary to determine the isotopic identity of assimilated nitrogen from two sources: the soil and the air. This study reports an isotopic value of fixed nitrogen by two alder species (Alnus incana (L.) Moench and Alnus glutinosa (L.) Gaertn. growing on nitrogen-free medium in greenhouse experiments. The δ15N value of the aerial parts was −2. This value was stable with time and did not depend on the Frankia strains used. This value could be used to estimate the nitrogen fixation in the natural ecosystem. Other parameters such as the mobilization of nitrogen reserves and the choice of the reference plant must be investigated to apply this method. The nodules of these two alder species were enriched in 15N relative to the rest of the plant but there was no relationship between symbiotic effectiveness of Frankia strains and 15N enrichment of nodules. On the other hand, for naturally growing trees, an enrichment in 15N was found primarily in the vesicles of nodules that are the sites of nitrogen fixation.

scholarly journals Loss of the nodule-specific cysteine rich peptide, NCR169, abolishes symbiotic nitrogen fixation in the Medicago truncatula dnf7 mutant

2015 ◽  
Vol 112 (49) ◽  
pp. 15232-15237 ◽  
Author(s):  
Beatrix Horváth ◽  
Ágota Domonkos ◽  
Attila Kereszt ◽  
Attila Szűcs ◽  
Edit Ábrahám ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Medicago Truncatula ◽  
Symbiotic Nitrogen Fixation ◽  
Root Nodules ◽  
Nitrogen Fixing ◽  
In Planta ◽  
Functional Roles ◽  
Absolute Requirement ◽  
Cell Layers

Host compatible rhizobia induce the formation of legume root nodules, symbiotic organs within which intracellular bacteria are present in plant-derived membrane compartments termed symbiosomes. In Medicago truncatula nodules, the Sinorhizobium microsymbionts undergo an irreversible differentiation process leading to the development of elongated polyploid noncultivable nitrogen fixing bacteroids that convert atmospheric dinitrogen into ammonia. This terminal differentiation is directed by the host plant and involves hundreds of nodule specific cysteine-rich peptides (NCRs). Except for certain in vitro activities of cationic peptides, the functional roles of individual NCR peptides in planta are not known. In this study, we demonstrate that the inability of M. truncatula dnf7 mutants to fix nitrogen is due to inactivation of a single NCR peptide, NCR169. In the absence of NCR169, bacterial differentiation was impaired and was associated with early senescence of the symbiotic cells. Introduction of the NCR169 gene into the dnf7-2/NCR169 deletion mutant restored symbiotic nitrogen fixation. Replacement of any of the cysteine residues in the NCR169 peptide with serine rendered it incapable of complementation, demonstrating an absolute requirement for all cysteines in planta. NCR169 was induced in the cell layers in which bacteroid elongation was most pronounced, and high expression persisted throughout the nitrogen-fixing nodule zone. Our results provide evidence for an essential role of NCR169 in the differentiation and persistence of nitrogen fixing bacteroids in M. truncatula.

scholarly journals Medicago truncatula Yellow Stripe-Like7 encodes a peptide transporter required for symbiotic nitrogen fixation

2020 ◽  
Author(s):  
Rosario Castro-Rodríguez ◽  
María Reguera ◽  
Viviana Escudero ◽  
Patricia Gil-Díez ◽  
Julia Quintana ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Transition Metal ◽  
Medicago Truncatula ◽  
Symbiotic Nitrogen Fixation ◽  
Root Nodules ◽  
Metal Homeostasis ◽  
Peptide Transporter ◽  
Short Peptides ◽  
Yellow Stripe ◽  
Mutant Lines

ABSTRACTYellow Stripe-Like (YSL) proteins are a family of plant transporters typically involved in transition metal homeostasis. The substrate of three of the four YSL clades (clades I, II, and IV) are metal complexes with non-proteinogenic amino acid nicotianamine or its derivatives. No such transport capabilities have been shown for any member of the remaining clade (clade III), which is able to translocate short peptides across the membranes instead. The connection between clade III YSL members and metal homeostasis might have been masked by the functional redundancy characteristic of this family. This might have been circumvented in legumes through neofunctionalization of YSLs to ensure a steady supply of transition metals for symbiotic nitrogen fixation in root nodules. To test this possibility, Medicago truncatula clade III transporter MtYSL7 has been studied both when the plant was fertilized with ammonium nitrate or when nitrogen had to be provided by endosymbiotic rhizobia within the root nodules. MtYSL7 is a plasma membrane protein expressed in the vasculature and in the nodule cortex. This protein is able to transport short peptides into the cytosol, although none with known metal homeostasis roles. Reducing MtYSL7 expression levels resulted in diminished nitrogen fixation rates. In addition, nodules of mutant lines lacking YSL7 accumulated more copper and iron, the later the likely result of increased expression in roots of iron uptake and delivery genes. The available data is indicative of a role of MtYSL7, and likely other clade III YSLs, in transition metal homeostasis.ONE SENTENCE SUMMARYMedicago truncatula YSL7 is a peptide transporter required for symbiotic nitrogen fixation in legume nodules, likely controlling transition metal allocation to these organs.

scholarly journals Recurrent mutualism breakdown events in a legume rhizobia metapopulation

2020 ◽  
Vol 287 (1919) ◽  
pp. 20192549 ◽  
Author(s):  
Kelsey A. Gano-Cohen ◽  
Camille E. Wendlandt ◽  
Khadija Al Moussawi ◽  
Peter J. Stokes ◽  
Kenjiro W. Quides ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Symbiotic Nitrogen Fixation ◽  
Root Nodules ◽  
Nitrogen Concentration ◽  
Phylogenetic Reconstruction ◽  
Nodulation Capacity ◽  
Host Growth ◽  
Native Legume ◽  
Fitness Benefits ◽  
Mutualism Breakdown

Bacterial mutualists generate major fitness benefits for eukaryotes, reshaping the host phenotype and its interactions with the environment. Yet, microbial mutualist populations are predicted to generate mutants that defect from providing costly services to hosts while maintaining the capacity to exploit host resources. Here, we examined the mutualist service of symbiotic nitrogen fixation in a metapopulation of root-nodulating Bradyrhizobium spp . that associate with the native legume Acmispon strigosus . We quantified mutualism traits of 85 Bradyrhizobium isolates gathered from a 700 km transect in California spanning 10 sampled A. strigosus populations. We clonally inoculated each Bradyrhizobium isolate onto A. strigosus hosts and quantified nodulation capacity and net effects of infection, including host growth and isotopic nitrogen concentration. Six Bradyrhizobium isolates from five populations were categorized as ineffective because they formed nodules but did not enhance host growth via nitrogen fixation. Six additional isolates from three populations failed to form root nodules. Phylogenetic reconstruction inferred two types of mutualism breakdown, including three to four independent losses of effectiveness and five losses of nodulation capacity on A. strigosus . The evolutionary and genomic drivers of these mutualism breakdown events remain poorly understood.

Metabolite Regulation of Phosphenolpyruvate Carboxylase in Legume Root Nodules

1996 ◽  
Vol 23 (4) ◽  
pp. 413 ◽  
Author(s):  
KC Woo ◽  
S Xu
Keyword(s):  
Nitrogen Fixation ◽  
Glycine Max ◽  
Vigna Unguiculata ◽  
Symbiotic Nitrogen Fixation ◽  
Feedback Inhibition ◽  
Root Nodules ◽  
Psophocarpus Tetragonolobus ◽  
Glycine Max L ◽  
Fructose 1,6 Bisphosphate ◽  
Metabolite Regulation

The effects of metabolic activators and inhibitors on phosphoenolpyruvate carboxylase (PEPC) activity were examined at pH 7 in partially purified enzyme from nodules of soybean (Glycine max (L.) Merr.), Psophocarpus tetragonolobus DC. and Vigna unguiculata ssp. sesquipedalis (L.) Verdc. Glucose 6-phosphate, fructose 6-phosphate, glucose 1-phosphate, fructose 1-phosphate, fructose 1,6- bisphosphate and phosphoglycerate stimulated the activity about 2-fold at low (0.5 mM) but not saturating (2.5 mM) PEP concentration. Glc 6-P and fru 6-P were the most effective activators and they increased the affinity of the enzyme for PEP by 2-4-fold. The dicarboxylates, malate, succinate, malonate, 2-oxoglutarate and aspartate inhibited PEPC activity. Malate was the most inhibitory, and strongly inhibited PEPC activity even at saturating PEP concentration. The Ki values for malate were 0.3-0.4 mM for soybean and P. tetragonolobus. However, glc 6-P and fru 6-P alleviated maiate inhibition and increased the Ki values by 11- to 28-fold in these two species. We propose that glc 6-P (fru 6-P) activates PEPC in a feedforward regulation and protects it against feedback inhibition by malate and thus coordinates the supply of photosynthate availability with malate synthesis required by the bacteroids to support symbiotic nitrogen fixation in nodules.

Symbiosomes: temporary moonlighting organelles

2014 ◽  
Vol 460 (1) ◽  
pp. 1-11 ◽  
Author(s):  
David W. Emerich ◽  
Hari B. Krishnan
Keyword(s):  
Nitrogen Fixation ◽  
Symbiotic Nitrogen Fixation ◽  
Infected Plant ◽  
Plant Cells ◽  
Fixed Nitrogen ◽  
Moonlighting Proteins ◽  
Biological Nitrogen ◽  
Structural Entity ◽  
Leguminous Host

Symbiosomes are a unique structural entity that performs the role of biological nitrogen fixation, an energy-demanding process that is the primary entryway of fixed nitrogen into the biosphere. Symbiosomes result from the infection of specific rhizobial strains into the roots of an appropriate leguminous host plant forming an organ referred to as a nodule. Within the infected plant cells of the nodule, the rhizobia are encased within membrane-bounded structures that develop into symbiosomes. Mature symbiosomes create an environment that allows the rhizobia to differentiate into a nitrogen-fixing form called bacteroids. The bacteroids are surrounded by the symbiosome space, which is populated by proteins from both eukaryotic and prokaryotic symbionts, suggesting this space is the quintessential component of symbiosis: an inter-kingdom environment with the single purpose of symbiotic nitrogen fixation. Proteins associated with the symbiosome membrane are largely plant-derived proteins and are non-metabolic in nature. The proteins of the symbiosome space are mostly derived from the bacteroid with annotated functions of carbon metabolism, whereas relatively few are involved in nitrogen metabolism. An appreciable portion of both the eukaryotic and prokaryotic proteins in the symbiosome are also ‘moonlighting’ proteins, which are defined as proteins that perform roles unrelated to their annotated activities when found in an unexpected physiological environment. The essential functions of symbiotic nitrogen fixation of the symbiosome are performed by co-operative interactions of proteins from both symbionts some of which may be performing unexpected roles.

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