scholarly journals Requirements for syrM and nodD Genes in the Nodulation of Medicago truncatula by Rhizobium meliloti 1021

1998 ◽  
Vol 11 (9) ◽  
pp. 937-940 ◽  
Author(s):  
Lucinda S. Smith ◽  
Sharon R. Long
Keyword(s):  
Medicago Sativa ◽  
Medicago Truncatula ◽  
Rhizobium Meliloti ◽  
Nodule Development ◽  
Wild Type ◽  
Bacterial Strains ◽  
Stringent Requirement ◽  
Plant System ◽  
Model Plant

Medicago truncatula, a relative of alfalfa (Medicago sativa), has been proposed as a model plant system for study of its interaction with the symbiont Rhizobium meliloti. Differences in M. truncatula and alfalfa may result in distinct symbiosis behaviors for the two hosts when in association with wild-type or mutant bacterial strains. We have found that M. truncatula has a more stringent requirement for syrM and nodD3 than is seen in alfalfa. In particular, the lack of syrM is associated with arrested nodule development.

scholarly journals MtBZR1 Plays an Important Role in Nodule Development in Medicago truncatula

2019 ◽  
Vol 20 (12) ◽  
pp. 2941
Author(s):  
Can Cui ◽  
Hongfeng Wang ◽  
Limei Hong ◽  
Yiteng Xu ◽  
Yang Zhao ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Normal Growth ◽  
Dry Mass ◽  
Growth Conditions ◽  
Nodule Development ◽  
Functional Study ◽  
Loss Of Function ◽  
Wild Type

Brassinosteroid (BR) is an essential hormone in plant growth and development. The BR signaling pathway was extensively studied, in which BRASSINAZOLE RESISTANT 1 (BZR1) functions as a key regulator. Here, we carried out a functional study of the homolog of BZR1 in Medicago truncatula R108, whose expression was induced in nodules upon Sinorhizobium meliloti 1021 inoculation. We identified a loss-of-function mutant mtbzr1-1 and generated 35S:MtBZR1 transgenic lines for further analysis at the genetic level. Both the mutant and the overexpression lines of MtBZR1 showed no obvious phenotypic changes under normal growth conditions. After S. meliloti 1021 inoculation, however, the shoot and root dry mass was reduced in mtbzr1-1 compared with the wild type, caused by partially impaired nodule development. The transcriptomic analysis identified 1319 differentially expressed genes in mtbzr1-1 compared with wild type, many of which are involved in nodule development and secondary metabolite biosynthesis. Our results demonstrate the role of MtBZR1 in nodule development in M. truncatula, shedding light on the potential role of BR in legume–rhizobium symbiosis.

The preference for strains of Rhizobium meliloti by cultivars of Medicago sativa grown on agar

1984 ◽  
Vol 30 (9) ◽  
pp. 1179-1183 ◽  
Author(s):  
E. S. P. Bromfield
Keyword(s):  
Antibiotic Resistance ◽  
Medicago Sativa ◽  
Parent Strain ◽  
Host Preference ◽  
Symbiotic Nitrogen Fixation ◽  
Rhizobium Meliloti ◽  
Wild Type ◽  
Rhizobium Strains ◽  
Axenic Conditions ◽  
Wild Type Parent

Variation in nodulation preference within and between cultivars of Medicago sativa for Rhizobium strains was assessed under axenic conditions using inocula consisting of paired strains of R. meliloti which could be recognized by distinctive colony morphology or antibiotic resistance. The largest variability in host preference for Rhizobium strains was among plants within cultivars and not between cultivars. The implications of such variation are discussed in the context of possible enhancement of symbiotic nitrogen fixation. An isolate of R. meliloti which had been marked with antibiotic resistance and cured of a cryptic plasmid was significantly less successful in nodulation than its wild-type parent strain in all inoculated combinations. The interaction of inoculum and cultivar on yield indicated differential symbiotic effectiveness of strains of R. meliloti on cultivars of M. sativa.

scholarly journals The Effect of Exogenous Nitrate on LCO Signalling, Cytokinin Accumulation, and Nodule Initiation in Medicago truncatula

Genes ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 988
Author(s):  
Kerstin Gühl ◽  
Rens Holmer ◽  
Ting Ting Xiao ◽  
Defeng Shen ◽  
Titis A. K. Wardhani ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Medicago Truncatula ◽  
Potent Inhibitor ◽  
Ethylene Biosynthesis ◽  
Wild Type ◽  
Biosynthesis Inhibitor ◽  
Signalling Molecules ◽  
Nodule Initiation

Nitrogen fixation by rhizobia is a highly energy-demanding process. Therefore, nodule initiation in legumes is tightly regulated. Environmental nitrate is a potent inhibitor of nodulation. However, the precise mechanism by which this agent (co)regulates the inhibition of nodulation is not fully understood. Here, we demonstrate that in Medicago truncatula the lipo-chitooligosaccharide-induced accumulation of cytokinins is reduced in response to the application of exogenous nitrate. Under permissive nitrate conditions, perception of rhizobia-secreted signalling molecules leads to an increase in the level of four cytokinins (i.e., iP, iPR, tZ, and tZR). However, under high-nitrate conditions, this increase in cytokinins is reduced. The ethylene-insensitive mutant Mtein2/sickle, as well as wild-type plants grown in the presence of the ethylene biosynthesis inhibitor 2-aminoethoxyvinyl glycine (AVG), is resistant to the inhibition of nodulation by nitrate. This demonstrates that ethylene biosynthesis and perception are required to inhibit nodule organogenesis under high-nitrate conditions.

scholarly journals Deletion of the SACPD-C Locus Alters the Symbiotic Relationship Between Bradyrhizobium japonicum USDA110 and Soybean, Resulting in Elicitation of Plant Defense Response and Nodulation Defects

2016 ◽  
Vol 29 (11) ◽  
pp. 862-877 ◽  
Author(s):  
Hari B. Krishnan ◽  
Alaa A. Alaswad ◽  
Nathan W. Oehrle ◽  
Jason D. Gillman
Keyword(s):  
Plant Defense ◽  
Defense Response ◽  
Acyl Carrier Protein ◽  
Defense Responses ◽  
Nodule Development ◽  
Plant Defense Response ◽  
Wild Type ◽  
Two Dimensional Gel Electrophoresis ◽  
Symbiotic Associations ◽  
Soybean Nodule

Legumes form symbiotic associations with soil-dwelling bacteria collectively called rhizobia. This association results in the formation of nodules, unique plant-derived organs, within which the rhizobia are housed. Rhizobia-encoded nitrogenase facilitates the conversion of atmospheric nitrogen into ammonia, which is utilized by the plants for its growth and development. Fatty acids have been shown to play an important role in root nodule symbiosis. In this study, we have investigated the role of stearoyl-acyl carrier protein desaturase isoform C (SACPD-C), a soybean enzyme that catalyzes the conversion of stearic acid into oleic acid, which is expressed in developing seeds and in nitrogen-fixing nodules. In-depth cytological investigation of nodule development in sacpd-c mutant lines M25 and MM106 revealed gross anatomical alteration in the sacpd-c mutants. Transmission electron microscopy observations revealed ultrastructural alterations in the sacpd-c mutants that are typically associated with plant defense response to pathogens. In nodules of two sacpd-c mutants, the combined jasmonic acid (JA) species (JA and the isoleucine conjugate of JA) were found to be reduced and 12-oxophytodienoic acid (OPDA) levels were significantly higher relative to wild-type lines. Salicylic acid levels were not significantly different between genotypes, which is divergent from previous studies of sacpd mutant studies on vegetative tissues. Soybean nodule phytohormone profiles were very divergent from those of roots, and root profiles were found to be almost identical between mutant and wild-type genotypes. The activities of antioxidant enzymes, ascorbate peroxidase, and superoxide dismutase were also found to be higher in nodules of sacpd-c mutants. PR-1 gene expression was extremely elevated in M25 and MM106, while the expression of nitrogenase was significantly reduced in these sacpd-c mutants, compared with the parent ‘Bay’. Two-dimensional gel electrophoresis and matrix-assisted laser desorption-ionization time of flight mass spectrometry analyses confirmed sacpd-c mutants also accumulated higher amounts of pathogenesis-related proteins in the nodules. Our study establishes a major role for SACPD-C activity as essential for proper maintenance of soybean nodule morphology and physiology and indicates that OPDA signaling is likely to be involved in attenuation of nodule biotic defense responses.

Expression of the nodulation and nitrogen fixation genes in Rhizobium meliloti during development

Genome ◽  
1989 ◽  
Vol 31 (1) ◽  
pp. 354-360 ◽  
Author(s):  
San Chiun Shen ◽  
Shui Ping Wang ◽  
Guan Qiao Yu ◽  
Jia Bi Zhu
Keyword(s):  
Nitrogen Fixation ◽  
Rhizobium Meliloti ◽  
Abnormal Development ◽  
Wild Type ◽  
Free Living ◽  
Nod Genes ◽  
Nodule Initiation ◽  
Fix Genes ◽  
Nitrogen Fixation Genes

Genes that specify nodulation (nod genes) are only active in the free-living rhizobia or in the nodule initiation state of rhizobia. As soon as the repression of nod genes occurs in the bacteroids of the nodule, nifA is induced, while ntrC is inactivated and thus the nifA-mediated nif/fix genes are turned on. Limitation of available oxygen brings about the induction of nifA, which reflects the actual status of nif/fix gene activities in symbiotic state of rhizobia. Oxygen thus appears to be a major symbiotic signal to the expression of bacteroid nif/fix genes. Mutation of nifA or shortage of nifA product in wild-type rhizobia caused by the inhibition of multicopy nifH/fixA promoters leads to an abnormal development of nodules and premature degradation of bacteroids in nodules.Key words: nitrogen fixation, nodulation, nif/fix regulation, nifA mutant.

Differential responses of the sunn4 and rdn1-1 super-nodulation mutants of Medicago truncatula to elevated atmospheric CO2

2021 ◽  
Author(s):  
Yunfa Qiao ◽  
Shujie Miao ◽  
Jian Jin ◽  
Ulrike Mathesius ◽  
Caixian Tang
Keyword(s):  
Nitrogen Fixation ◽  
Elevated Co2 ◽  
Medicago Truncatula ◽  
N2 Fixation ◽  
Sink Strength ◽  
Wild Type ◽  
Total N ◽  
Autoregulation Of Nodulation ◽  
Nodulation Mutants ◽  
Fixation Capacity

Abstract Background and Aims Nitrogen fixation in legumes requires tight control of carbon and nitrogen balance. Thus, legumes control nodule numbers via an autoregulation mechanism. ‘Autoregulation of nodulation’ mutants super-nodulate and are thought to be carbon-limited due to the high carbon-sink strength of excessive nodules. This study aimed to examine the effect of increasing carbon supply on the performance of super-nodulation mutants. Methods We compared the responses of Medicago truncatula super-nodulation mutants (sunn-4 and rdn1-1) and wild type to five CO2 levels (300-850 μmol mol -1). Nodule formation and N2 fixation were assessed in soil-grown plants at 18 and 42 days after sowing. Key results Shoot and root biomass, nodule number and biomass, nitrogenase activity and fixed-N per plant of all genotypes increased with increasing CO2 concentration and reached the maximum around 700 μmol mol -1. While the sunn-4 mutant showed strong growth-retardation compared to wild-type plants, elevated CO2 increased shoot biomass and total N content of rdn1-1 mutant up to two-fold. This was accompanied by a four-fold increase in nitrogen fixation capacity in the rdn1-1 mutant. Conclusions These results suggest that the super-nodulation phenotype per se did not limit growth. The additional nitrogen fixation capacity of the rdn1-1 mutant may enhance the benefit of elevated CO2 on plant growth and N2 fixation.

scholarly journals Inoculation with Efficient Nitrogen Fixing and Indoleacetic Acid Producing Bacterial Microsymbiont Enhance Tolerance of the Model LegumeMedicago truncatulato Iron Deficiency

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Nadia Kallala ◽  
Wissal M’sehli ◽  
Karima Jelali ◽  
Zribi Kais ◽  
Haythem Mhadhbi
Keyword(s):  
Oxidative Stress ◽  
Iron Deficiency ◽  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Plant Biomass ◽  
High Growth ◽  
Fe Deficiency ◽  
Nitrogen Fixing ◽  
Bacterial Strains ◽  
Negative Effect

The aim of this study was to assess the effect of symbiotic bacteria inoculation on the response ofMedicago truncatulagenotypes to iron deficiency. The present work was conducted on threeMedicago truncatulagenotypes: A17, TN8.20, and TN1.11. Three treatments were performed: control (C), direct Fe deficiency (DD), and induced Fe deficiency by bicarbonate (ID). Plants were nitrogen-fertilized (T) or inoculated with two bacterial strains:Sinorhizobium melilotiTII7 andSinorhizobium medicaeSII4. Biometric, physiological, and biochemical parameters were analyzed. Iron deficiency had a significant lowering effect on plant biomass and chlorophyll content in allMedicago truncatulagenotypes. TN1.11 showed the highest lipid peroxidation and leakage of electrolyte under iron deficiency conditions, which suggest that TN1.11 was more affected than A17 and TN8.20 by Fe starvation. Iron deficiency affected symbiotic performance indices of allMedicago truncatulagenotypes inoculated with bothSinorhizobiumstrains, mainly nodules number and biomass as well as nitrogen-fixing capacity. Nevertheless, inoculation withSinorhizobiumstrains mitigates the negative effect of Fe deficiency on plant growth and oxidative stress compared to nitrogen-fertilized plants. The highest auxin producing strain, TII7, preserves relatively high growth and root biomass and length when inoculated to TN8.20 and A17. On the other hand, both TII7 and SII4 strains improve the performance of sensitive genotype TN1.11 through reduction of the negative effect of iron deficiency on chlorophyll and plant Fe content. The bacterial inoculation improved Fe-deficient plant response to oxidative stress via the induction of the activities of antioxidant enzymes.

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