scholarly journals Physical Environment and Symbiotic Nitrogen Fixation III. Root Temperature Effects on Shoot and Root Development and Nitrogen Distribution In Trifolium Subterraneum

1966 ◽  
Vol 19 (2) ◽  
pp. 219 ◽  
Author(s):  
AH Gibson
Keyword(s):  
Nitrogen Fixation ◽  
Physical Environment ◽  
Temperature Effects ◽  
Shoot Growth ◽  
Symbiotic Nitrogen Fixation ◽  
Root Nodules ◽  
Trifolium Subterraneum ◽  
Root Temperature ◽  
Nitrogen Distribution ◽  
Root And Shoot Growth

Root and shoot growth, and the distribution of nitrogen to the roots and shoots, were examined in five varieties of Trifolium subterraneum. The plants were grown between 5 and 30�0 root temperature, and received their nitrogen from root nodules, or as ammonium nitrate.

scholarly journals Physical Environment and Symbiotic Nitrogen Fixation II. Root Temperature Effects on the Relative Nitrogen Assimilation Rate

1965 ◽  
Vol 18 (2) ◽  
pp. 295 ◽  
Author(s):  
AH Gibson
Keyword(s):  
Nitrogen Fixation ◽  
Physical Environment ◽  
Temperature Effects ◽  
Nitrogen Assimilation ◽  
Symbiotic Nitrogen Fixation ◽  
Trifolium Subterraneum ◽  
Bacterial Strains ◽  
Root Temperature ◽  
Relative Growth ◽  
Relative Growth Rates

Nitrogen fixation by six varieties of Trifolium subterraneum L., each inoculated with a number of strains of Rhizobium trifolii, was examined over a range of root temperatures. Significant differences in the rate of nodule establishment and early nitrogen fixation were found between varieties, and between bacterial strains. In order to minimize the effect of such differences, relative nitrogen assimilation rates (RN) and relative growth rates (R w) were used to compare the different legume-bacteria associations.

scholarly journals Physical Environment and Symbiotic Nitrogen Fixation. IV. Faotors Affecting the Early Stages of Nodulation

1967 ◽  
Vol 20 (6) ◽  
pp. 1087 ◽  
Author(s):  
AH Gibson
Keyword(s):  
Nitrogen Fixation ◽  
Physical Environment ◽  
Symbiotic Nitrogen Fixation ◽  
Trifolium Subterraneum ◽  
Light Period ◽  
Root Temperature ◽  
Early Stages ◽  
Temperature Conditions ◽  
General Decline ◽  
Effect Of Light

The influence of root temperature on the initial nodulation of Trifolium subterraneum L. was examined, and observations were made on the effect of light period and shoot temperature on this character. The maximum constant root temperature at which nodules would form was 33�0, and the minimum was in the vicinity of 7�0. The most rapid initial nodulation (2-3 days after inoculation) was observed at 30�0, and plants growing at this temperature had the highest rate of nodule appearance. Below 22�0, there was a marked increase in the "time to first visible nodule" and a general decline in the rate at which they appeared. Differences were observed in the time to first visible nodule, and in the rate of nodule appearance, between different cultivars of T. 8ubterraneum. There was an indication of a temperature X cultivar interaction for these characters. With the three strains of Rh. trifolii used, no differences in their ability to form nodules were observed, although it was known that their subsequent symbiotic behaviour differed under certain root temperature conditions.

scholarly journals Physical Environment and Symbiotic Nitrogen Fixation VI. Nitrogen Retention Within the Nodules of Trifolium Subterraneum L

1969 ◽  
Vol 22 (4) ◽  
pp. 829 ◽  
Author(s):  
AH Gibson
Keyword(s):  
Nitrogen Fixation ◽  
Physical Environment ◽  
Effective Strain ◽  
Nitrogen Retention ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Root Temperature ◽  
Protein Nitrogen ◽  
The Difference ◽  
Nodule Tissue

The effect of bacterial strain and root temperature on the retention of nitrogen in the root system of Trifolium Bubterraneum plants was re-examined. The root systems of plants nodulated by the moderately effective Rhizobium trifolii strain NA30 possessed a higher percentage nitrogen than those nodulated by the fully effective strain TAl, although the number of nodules formed by each strain was similar. The difference was due to a greater weight of nodule tissue on the NA30-nodulated plants, and also to a higher percentage nitrogen in the NA30 nodules; this latter effect was due to a higher concentration of non-protein nitrogen. The overall effect of these differences was to reduce the amount of nitrogen translocated to the shoots of the NA30 plants, in both absolute terms and as a proportion of the total amount of nitrogen fixed. Another difference between the two strains was the rate of nitrogen fixation per unit (dry weight or leghaemoglobin content) of nodule tissue.

scholarly journals Physical Environment and Symbiotic Nitrogen Fixation VII. Effect of Fluctuating Root Temperature on Nitrogen Fixation

1969 ◽  
Vol 22 (4) ◽  
pp. 839 ◽  
Author(s):  
AH Gibson
Keyword(s):  
Nitrogen Fixation ◽  
Physical Environment ◽  
Symbiotic Nitrogen Fixation ◽  
Dark Period ◽  
Light Period ◽  
Continuous Illumination ◽  
Continuous Exposure ◽  
Rhizobium Trifolii ◽  
Symbiotic System ◽  
Root Temperature

The effect of exposing nodulated plants to daily periods of high, moderate, or low root temperatures was examined, using Trifolium 8ubterraneum and three strains of Rhizobium trifolii. With strains whose nitrogen fixation was severely retarded by continuous exposure to high root temperatures, the results from treatments involving exposure of 4, 8, 12, and 20 hr/day to 30�C and continuous illumination were consistent with the effect being on the rate of nitrogen fixation, without any permanent impairment to the symbiotic system. With a 12 hr/day light period, a daily 12-hr exposure to 30�C during the dark period reduced total nitrogen fixation as much as exposure to 30�C during the light period. This indicated that the rate of nitrogen fixation during normal dark periods could be as high as that during periods of illumination. Similar conclusions were drawn from the same type of experiments involving daily exposure to moderate (14 and 16�C) root temperatures.

scholarly journals Physical Environment and Symbiotic Nitrogen Fixation

1963 ◽  
Vol 16 (1) ◽  
pp. 28 ◽  
Author(s):  
AH Gibson
Keyword(s):  
Nitrogen Fixation ◽  
Physical Environment ◽  
Symbiotic Nitrogen Fixation ◽  
Trifolium Subterraneum ◽  
Rhizobium Trifolii

The effect of root temperatures (5-30�0) on the growth and symbiotic nitrogen fixation by nodulated plants of four varieties of Trifolium subterraneum L., inoculated with each of two strains of Rhizobium trifolii, was examined.

scholarly journals Physical Environment and Symbiotic Nitrogen Fixation. V. Effect of Time of Exposure to Unfavourable Root Temperatures

1967 ◽  
Vol 20 (6) ◽  
pp. 1105 ◽  
Author(s):  
AH Gibson
Keyword(s):  
Nitrogen Fixation ◽  
Physical Environment ◽  
Symbiotic Nitrogen Fixation ◽  
Trifolium Subterraneum ◽  
Dry Weight ◽  
Rhizobium Trifolii ◽  
Optimal Temperature ◽  
Three Stages

Symbiotic nitrogen fixation by Trifolium subterraneum L., inoculated with three strains of Rhizobium trifolii Dang., was examined over the range of root temperatures 8-28�0. The plants were transferred from an optimal temperature for nitrogen fixation (23�0) to other temperatures at three stages, namely (1) immediately after inoculation, 3 days after germination, (2) 14 days after germ� ination, when nitrogen fixation had commenced, and (3) 21 days after germination, when the plants had been fixing nitrogen for at least 7 days. Nitrogen increase and dry weight accumulation were determined for two growth periods-days 14-21 (I) and days 21-28 (II)

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.

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.

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