scholarly journals Ionic transporters in the root nodule of Medicago truncatula: membrane antiporters Na+/H+

2020 ◽  
Author(s):  
N. A. Trifonova ◽  
M. I. Korolyova ◽  
E. E. Fedorova
Keyword(s):  
Electron Microscopy ◽  
Salt Stress ◽  
Medicago Truncatula ◽  
Root Nodule ◽  
Root Nodules ◽  
Ionic Transporters ◽  
Confocal And Electron Microscopy

In root nodules of Medicago truncatula subjected to salt stress the level of expression of Na+/H+ antiporters NHX1 and NHX7 was estimated. The localization of NHX1 was studied by confocal and electron microscopy.

scholarly journals Inhibition of Glutamine Synthetase by Phosphinothricin Leads to Transcriptome Reprograming in Root Nodules of Medicago truncatula

2012 ◽  
Vol 25 (7) ◽  
pp. 976-992 ◽  
Author(s):  
Ana R. Seabra ◽  
Patrícia A. Pereira ◽  
Jörg D. Becker ◽  
Helena G. Carvalho
Keyword(s):  
Glutamine Synthetase ◽  
Medicago Truncatula ◽  
Root Nodule ◽  
Higher Plants ◽  
Cell Metabolism ◽  
Root Nodules ◽  
Organic N ◽  
N Availability ◽  
Time Points ◽  
N Assimilation

Glutamine synthetase (GS) is a vital enzyme for the assimilation of ammonia into amino acids in higher plants. In legumes, GS plays a crucial role in the assimilation of the ammonium released by nitrogen-fixing bacteria in root nodules, constituting an important metabolic knob controlling the nitrogen (N) assimilatory pathways. To identify new regulators of nodule metabolism, we profiled the transcriptome of Medicago truncatula nodules impaired in N assimilation by specifically inhibiting GS activity using phosphinothricin (PPT). Global transcript expression of nodules collected before and after PPT addition (4, 8, and 24 h) was assessed using Affymetrix M. truncatula GeneChip arrays. Hundreds of genes were regulated at the three time points, illustrating the dramatic alterations in cell metabolism that are imposed on the nodules upon GS inhibition. The data indicate that GS inhibition triggers a fast plant defense response, induces premature nodule senescence, and promotes loss of root nodule identity. Consecutive metabolic changes were identified at the three time points analyzed. The results point to a fast repression of asparagine synthesis and of the glycolytic pathway and to the synthesis of glutamate via reactions alternative to the GS/GOGAT cycle. Several genes potentially involved in the molecular surveillance for internal organic N availability are identified and a number of transporters potentially important for nodule functioning are pinpointed. The data provided by this study contributes to the mapping of regulatory and metabolic networks involved in root nodule functioning and highlight candidate modulators for functional analysis.

Ultrastructural evidence for the existence of actinorhizal symbioses in the late Pleistocene

1980 ◽  
Vol 58 (15) ◽  
pp. 1612-1620 ◽  
Author(s):  
Dwight Baker ◽  
Norton G. Miller
Keyword(s):  
Electron Microscopy ◽  
Root Nodule ◽  
Root Nodules ◽  
Eastern North America ◽  
Independent Evidence ◽  
Qualitative And Quantitative ◽  
Ultrastructural Evidence ◽  
Shepherdia Canadensis ◽  
Nodule Endophytes ◽  
Scanning Electron

Macrofossil actinorhizal root nodules discovered in sediments about 11 500 radiocarbon years old in northern Vermont, U.S.A., were studied by scanning electron microscopy. Evidence of an endophytic microsymbiont was observed within the cortex of the fossil nodules. A comparative study as undertaken using root nodules from species of Alnus, Dryas, Elaeagnus, Myrica, Shepherdia, and Vicia native to eastern North America in an effort to determine the identity of the fossils. From qualitative and quantitative differences observed among the root nodule endophytes, it was concluded that the fossil nodules contained actinomycetes morphologically similar to those of extant Elaeagnaceae. The fossils are probably from plants of Elaeagnus commutata and (or) Shepherdia canadensis based on independent evidence of the representation of these species in the plant macrofossil assemblage.

Ultrastructure of the Alnus crispa var. mollis Fern. root nodule endophyte

1975 ◽  
Vol 21 (7) ◽  
pp. 1058-1080 ◽  
Author(s):  
Maurice Lalonde ◽  
Roger Knowles
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Root Nodule ◽  
Root Nodules ◽  
Host Cells ◽  
Alnus Crispa ◽  
Transmission Electron ◽  
Host Cell Wall ◽  
Capsular Material ◽  
Nodule Endophytes

Nitrogen-fixing, field-obtained root nodules of the silky green alder were studied by transmission electron microscopy. The nodule endophyte exhibited a prokaryotic cytology and was present in two forms: the hypha (0.3–1.0 μm), which was branched and septate, and the vesicle (3–5 μm), which was also septate and developed at the parental hypha tip. Bacteria-like cells, previously observed in light microscopy studies, were not seen in the present work. The actinomycete-like endophyte penetrated through the host cell wall and became enveloped by a capsular material (0.1 μm), the whole being enclosed by host membranes. In some host cells, the endophyte appeared to lyse and become a mass of shrunken debris. The fine structure of the Alnus crispa var. mollis root nodule endophyte was found to be similar to that of other non-leguminous root nodule endophytes.

scholarly journals Salt stress enhances early symbiotic gene expression in Medicago truncatula and induces a stress-specific set of rhizobium-responsive genes.

2021 ◽  
Author(s):  
Sanhita Chakraborty ◽  
Heather Driscoll ◽  
Juan Abrahante Lloréns ◽  
Fan Zhang ◽  
Robert Fisher ◽  
...  
Keyword(s):  
Gene Expression ◽  
Salt Stress ◽  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Root Nodules ◽  
Symbiotic Association ◽  
Symbiotic Gene ◽  
Nod Factor ◽  
Early Nodulin ◽  
Regulated Gene Expression

Salt stress is a major agricultural concern inhibiting not only plant growth but also the symbiotic association between legume roots and the soil bacteria rhizobia. This symbiotic association is initiated by a molecular dialogue between the two partners, leading to the activation of a signaling cascade in the legume host and ultimately the formation of nitrogen-fixing root nodules. Here we show that a moderate salt stress increases the responsiveness of early symbiotic genes in Medicago truncatula to its symbiotic partner, Sinorhizobium meliloti, while conversely, inoculation with S. meliloti counteracts salt-regulated gene expression, restoring one-third to control levels. Our analysis of Early Nodulin 11 shows that salt-induced expression is dynamic, Nod-factor dependent, and requires the ionic, but not the osmotic, component of salt. We demonstrate that salt stimulation of rhizobium-induced gene expression requires NSP2, which functions as a node to integrate the abiotic and biotic signals. In addition, our work reveals that inoculation with Sinorhizobium meliloti succinoglycan mutants also hyperinduces ENOD11 expression in the presence or absence of salt, suggesting a possible link between rhizobial exopolysaccharide and the plant response to salt stress. Finally, we identify an accessory set of genes that are induced by rhizobium only under conditions of salt stress and have not been previously identified as being nodulation-related genes. Our data suggests that interplay of core nodulation genes with different accessory sets, specific for different abiotic conditions, function to establish the symbiosis. Together, our findings reveal a complex and dynamic interaction between plant, microbe, and environment.

scholarly journals Potassium content diminishes in infected cells of Medicago truncatula nodules due to the mislocation of channels MtAKT1 and MtSKOR/GORK

2020 ◽  
Author(s):  
Elena E Fedorova ◽  
Teodoro Coba de la Peña ◽  
Victoria Lara-Dampier ◽  
Natalia A Trifonova ◽  
Olga Kulikova ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Root Nodule ◽  
Root Nodules ◽  
Phylogenetic Analyses ◽  
Gene Copy ◽  
Gene Localization ◽  
K Channel ◽  
Infected Cells ◽  
Plant Ion Channels ◽  
Mature Nodule

Root nodule-infected cells have defects in K+ balance, as compared with non-infected cells, probably due to variation in the location of K+ channel proteins MtAKT1 and MtSKOR/GORK. Abstract Rhizobia establish a symbiotic relationship with legumes that results in the formation of root nodules, where bacteria encapsulated by a membrane of plant origin (symbiosomes), convert atmospheric nitrogen into ammonia. Nodules are more sensitive to ionic stresses than the host plant itself. We hypothesize that such a high vulnerability might be due to defects in ion balance in the infected tissue. Low temperature SEM (LTSEM) and X-ray microanalysis of Medicago truncatula nodules revealed a potassium (K+) decrease in symbiosomes and vacuoles during the life span of infected cells. To clarify K+ homeostasis in the nodule, we performed phylogenetic and gene expression analyses, and confocal and electron microscopy localization of two key plant Shaker K+ channels, AKT1 and SKOR/GORK. Phylogenetic analyses showed that the genome of some legume species, including the Medicago genus, contained one SKOR/GORK and one AKT1 gene copy, while other species contained more than one copy of each gene. Localization studies revealed mistargeting and partial depletion of both channels from the plasma membrane of M. truncatula mature nodule-infected cells that might compromise ion transport. We propose that root nodule-infected cells have defects in K+ balance due to mislocation of some plant ion channels, as compared with non-infected cells. The putative consequences are discussed.

scholarly journals Aeration Pathways in Soybean Root Nodules

1973 ◽  
Vol 26 (4) ◽  
pp. 729 ◽  
Author(s):  
FJ Bergersen ◽  
DJ Goodchild
Keyword(s):  
Electron Microscopy ◽  
Root Nodule ◽  
Root Nodules ◽  
Light And Electron Microscopy ◽  
Intercellular Spaces ◽  
Soybean Root

Soybean root nodule tissues contain many interconnected gas-filled intercellular spaces. They have been studied, in fresh and embedded tissue during the development and functional life of the nodules, by light and electron microscopy.

scholarly journals Aboveground plant-to-plant communication reduces root nodule symbiosis and soil nutrient concentrations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuta Takahashi ◽  
Kaori Shiojiri ◽  
Akira Yamawo
Keyword(s):  
Root Nodule ◽  
Total Phenolics ◽  
Root Nodules ◽  
Soil Nutrient ◽  
Chemical Defenses ◽  
Nutrient Concentrations ◽  
Soil C ◽  
Plant Communication ◽  
Root Nodule Symbiosis ◽  
Nodule Symbiosis

AbstractAboveground communication between plants is well known to change defense traits in leaves, but its effects on belowground plant traits and soil characteristics have not been elucidated. We hypothesized that aboveground plant-to-plant communication reduces root nodule symbiosis via induction of bactericidal chemical defense substances and changes the soil nutrient environment. Soybean plants were exposed to the volatile organic compounds (VOCs) from damaged shoots of Solidago canadensis var. scabra, and leaf defense traits (total phenolics, saponins), root saponins, and root nodule symbiosis traits (number and biomass of root nodules) were measured. Soil C/N ratios and mineral concentrations were also measured to estimate the effects of resource uptake by the plants. We found that total phenolics were not affected. However, plants that received VOCs had higher saponin concentrations in both leaves and roots, and fewer root nodules than untreated plants. Although the concentrations of soil minerals did not differ between treatments, soil C/N ratio was significantly higher in the soil of communicated plants. Thus, the aboveground plant-to-plant communication led to reductions in root nodule symbiosis and soil nutrient concentrations. Our results suggest that there are broader effects of induced chemical defenses in aboveground plant organs upon belowground microbial interactions and soil nutrients, and emphasize that plant response based on plant-to-plant communications are a bridge between above- and below-ground ecosystems.

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