Symbiotic characteristics of Rhizobium meliloti: and appraisal of the systematic treatment of nodulation and nitrogen fixation interactions between hosts and Rhizobia of diverse origins

1966 ◽  
Vol 17 (6) ◽  
pp. 885 ◽  
Author(s):  
J Brockwell ◽  
FW Hely
Keyword(s):  
Nitrogen Fixation ◽  
Host Species ◽  
Rhizobium Meliloti ◽  
Small Degree ◽  
Nodule Formation ◽  
Systematic Treatment ◽  
Diverse Origin ◽  
Medicago Rugosa ◽  
Medicago Sativa L ◽  
Symbiotic Properties

The symbiotic properties of 42 isolates of Rhizobium meliloti collected from widely separated sites in the upper basin of the Darling River were tested in bacteriologically controlled culture with 18 species and varieties of Medicago, three species of Melilotus, and one species of Trigonella. Seven strains of Rh. Meliloti of commercial interest were included in the experiments for comparative purposes. Nodule formation occurred on all plants in 889 out of 974 symbiotic combinations examined. Only Medicago laciniata (L.) Mill, among the hosts and the isolate from M. laciniata among the rhizobia exhibited distinctive nodule formation behaviour. Nitrogen fixation occurred in 637 combinations. On the basis of nitrogen fixation, eight groups of Rh. Meliloti were recognized; there were nine host groups. The groups could be arranged in an interlocking pattern of increasing host and bacterial specificity. These results, which modified to a small degree the bacterial and host groupings previously reported, strongly suggested that the pattern will be widely applicable to Rh. meliloti of diverse origin. In general, the isolates examined were promiscuous and 24 were capable of effective symbioses in association with 10 or more of the hosts. M. laciniata, Trigonella suavissima Lindl., and Medicago rugosa Desr. were the hosts most highly strain-specific in their requirements for nitrogen fixation, and Medicago sativa L. was the most promiscuous. A system for classifying host species into compatibility groups is proposed.

scholarly journals Rhizobium issues affecting the contribution of caucasian clover to New Zealand pastoral agriculture

1998 ◽  
pp. 207-211
Author(s):  
R.M. Elliot ◽  
H.J. Mcintyre ◽  
B.C. Challis ◽  
H.N. Pryor ◽  
W.L. Lowther ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
New Zealand ◽  
White Clover ◽  
Nodule Formation ◽  
Trifolium Ambiguum ◽  
Field Environment ◽  
Large Populations ◽  
Symbiotic Properties ◽  
Undesirable Property ◽  
Over Time

Caucasian clover (Trifolium ambiguum) is being commercially released for use in New Zealand agriculture. Seed must be inoculated at sowing, as caucasian clover forms a nitrogen-fixing symbiosis only with specific rhizobia that are not native to New Zealand. These rhizobia have the potentially undesirable property of readily forming nodules on white clover that do not fix nitrogen. Caucasian clover inoculant strains available for use in New Zealand were found to be genetically unstable in the laboratory, and must be frequently monitored for their symbiotic properties. A strain of caucasian clover rhizobia that gives better establishment and growth of caucasian clover under oversowing conditions was identified. This strain maintained a higher level of viability under stress conditions in the laboratory and showed enhanced survival on seed in the environment. Growth of caucasian clover results in large populations of caucasian clover rhizobia in the soil. These formed nodules on white clover in the same field environment, although white clover rhizobia dominated nodule formation. Nevertheless it is possible that present caucasian clover inoculants may over time reduce nitrogen fixation and hence the production and persistence of white clover. Further research is required to develop a caucasian clover strain that does not form ineffective nodules on white clover. Keywords: caucasian clover, inoculation, nodulation, rhizobia, Trifolium ambiguum, Trifolium repens, white clover

EFFECTS OF SOIL ACIDITY ON RHIZOBIA NUMBERS, NODULATION AND NITROGEN FIXATION BY ALFALFA AND RED CLOVER

1977 ◽  
Vol 57 (2) ◽  
pp. 197-203 ◽  
Author(s):  
W. A. RICE ◽  
D. C. PENNEY ◽  
M. NYBORG
Keyword(s):  
Nitrogen Fixation ◽  
Soil Ph ◽  
Soil Acidity ◽  
Field Experiments ◽  
Rhizobium Meliloti ◽  
Acid Soils ◽  
Red Clover ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Greenhouse Experiments

The effects of soil acidity on nitrogen fixation by alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were investigated in field experiments at 28 locations, and in greenhouse experiments using soils from these locations. The pH of the soils (limed and unlimed) varied from 4.5 to 7.2. Rhizobia populations in the soil, nodulation, and relative forage yields (yield without N/yield with N) were measured in both the field and greenhouse experiments. Rhizobium meliloti numbers, nodulation scores, and relative yields of alfalfa decreased sharply as the pH of the soils decreased below 6.0. For soils with pH 6.0 or greater, there was very little effect of pH on any of the above factors for alfalfa. Soil pH in the range studied had no effect on nodulation scores and relative yields of red clover. However, R. trifolii numbers were reduced when the pH of the soil was less than 4.9. These results demonstrate that hydrogen ion concentration is an important factor limiting alfalfa growth on acid soils of Alberta and northeastern British Columbia, but it is less important for red clover. This supports the continued use of measurements of soil pH, as well as plant-available Al and Mn for predicting crop response to lime.

scholarly journals Chickpea shows genotype-specific nodulation responses across soil nitrogen environment and root disease resistance categories

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Krista L. Plett ◽  
Sean L. Bithell ◽  
Adrian Dando ◽  
Jonathan M. Plett
Keyword(s):  
Nitrogen Fixation ◽  
Disease Resistance ◽  
Soil Nitrogen ◽  
Cellular Localization ◽  
Expression Patterns ◽  
Nodule Development ◽  
Nodule Formation ◽  
Symbiotic Relationship ◽  
Plant Genotype ◽  
Factors Affecting

Abstract Background The ability of chickpea to obtain sufficient nitrogen via its symbiotic relationship with Mesorhizobium ciceri is of critical importance in supporting growth and grain production. A number of factors can affect this symbiotic relationship including abiotic conditions, plant genotype, and disruptions to host signalling/perception networks. In order to support improved nodule formation in chickpea, we investigated how plant genotype and soil nutrient availability affect chickpea nodule formation and nitrogen fixation. Further, using transcriptomic profiling, we sought to identify gene expression patterns that characterize highly nodulated genotypes. Results A study involving six chickpea varieties demonstrated large genotype by soil nitrogen interaction effects on nodulation and further identified agronomic traits of genotypes (such as shoot weight) associated with high nodulation. We broadened our scope to consider 29 varieties and breeding lines to examine the relationship between soilborne disease resistance and the number of nodules developed and real-time nitrogen fixation. Results of this larger study supported the earlier genotype specific findings, however, disease resistance did not explain differences in nodulation across genotypes. Transcriptional profiling of six chickpea genotypes indicates that genes associated with signalling, N transport and cellular localization, as opposed to genes associated with the classical nodulation pathway, are more likely to predict whether a given genotype will exhibit high levels of nodule formation. Conclusions This research identified a number of key abiotic and genetic factors affecting chickpea nodule development and nitrogen fixation. These findings indicate that an improved understanding of genotype-specific factors affecting chickpea nodule induction and function are key research areas necessary to improving the benefits of rhizobial symbiosis in chickpea.

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.

Overexpression of the dctA gene in Rhizobium meliloti: effect on transport of C4 dicarboxylates and symbiotic nitrogen fixation

1992 ◽  
Vol 38 (6) ◽  
pp. 555-562 ◽  
Author(s):  
Vipin Rastogi ◽  
Monika Labes ◽  
Turlough Finan ◽  
Robert Watson
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Symbiotic Nitrogen Fixation ◽  
Plasmid Stability ◽  
Rhizobium Meliloti ◽  
Mrna Synthesis ◽  
Dicarboxylate Transport ◽  
Fusion Strain ◽  
Tryptophan Operon ◽  
Specific Mrna

Symbiotic nitrogen fixation may be limited by the transport of C4 dicarboxylates into bacteroids in the nodule for use as a carbon and energy source. In an attempt to increase dicarboxylate transport, a plasmid was constructed in which the Rhizobium meliloti structural transport gene dctA was fused to a tryptophan operon promoter from Salmonella typhimurium, trpPO. This resulted in a functional dctA gene that was no longer under the control of the dctBD regulatory genes, but the recombinant plasmid was found to be unstable in R. meliloti. To stably integrate the trpPO-dctA fusion, it was recloned into pBR325 and recombined into the R. meliloti exo megaplasmid in the dctABD region. The resultant strain showed constitutive dctA-specific mRNA synthesis which was about 5-fold higher than that found in fully induced wild-type cells. Uptake assays showed that [14C]succinate transport by the trpPO-dctA fusion strain was constitutive, and the transport rate was the same as that of induced control cells. Acetylene reduction assays indicated a significantly higher rate of nitrogen fixation in plants inoculated with the trpPO-dctA fusion strain compared with the control. Despite this apparent increase, the plants had the same top dry weights as those inoculated with control cells. Key words: acetylene reduction, genetic engineering, nodule, plasmid stability, promoter.

Systemic control of nodule formation by the plant N demand requires autoregulation dependent and independent mechanisms

2021 ◽  
Author(s):  
Marjorie Pervent ◽  
Ilana Lambert ◽  
Marc Tauzin ◽  
Alicia Karouani ◽  
Martha Nigg ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Nodule Formation ◽  
Atmospheric Nitrogen ◽  
Plant Nitrogen ◽  
Systemic Signaling ◽  
Systemic Control ◽  
Whole Plant ◽  
Strong Control ◽  
Mutant Genes ◽  
N Demand

Abstract In legumes interacting with rhizobia the formation of symbiotic organs involved in the acquisition of atmospheric nitrogen is depending of the plant nitrogen (N) demand. We used Medicago truncatula plants cultivated in split-root systems to discriminate between responses to local and systemic N signalings. We evidenced a strong control of nodule formation by systemic N-signaling but obtained no clear evidence of a local control by mineral nitrogen. Systemic signaling of the plant N demand controls numerous transcripts involved in the root transcriptome reprogramming associated to early rhizobia interaction and nodule formation. SUNN has an important role in this control but major systemic N signaling responses remained active in the sunn mutant. Genes involved in the activation of nitrogen fixation are regulated by systemic N signaling in the mutant, explaining why the hypernodulation phenotype is not associated to a higher nitrogen fixation of the whole plant. The control of the transcriptome reprogramming of nodule formation by systemic N signaling requires other pathway(s) that parallel the SUNN/CLE pathway.

Application of biochemical studies to improving nitrogen fixation

2001 ◽  
Vol 41 (3) ◽  
pp. 403 ◽  
Author(s):  
C. P. Vance ◽  
J. F. S. Lamb
Keyword(s):  
Nitrogen Fixation ◽  
Plant Breeding ◽  
Microbial Ecology ◽  
Carbon Metabolism ◽  
Multidisciplinary Approach ◽  
Symbiotic Nitrogen Fixation ◽  
Plant Biochemistry ◽  
Biochemical Studies ◽  
Plant Genes ◽  
Medicago Sativa L

Improvement of symbiotic nitrogen fixation requires a multidisciplinary approach with a comprehensive program ranging from microbial ecology to plant breeding and genomics. Achievement of symbiotic nitrogen fixation requires at least 100 genes from each partner interacting in a favorable environment. The more information that we obtain from applied and fundamental studies of Rhizobium–legume and Frankia–non-legume symbioses, the greater are our chances to extend nitrogen fixation to non-fixing species. Studies with alfalfa (Medicago sativa L.) aimed at improving symbiotic nitrogen fixation have resulted in significant advances in germplasm development, plant biochemistry, microbial ecology and the understanding of plant genes involved in nodule nitrogen and carbon metabolism. However, translation to field improvement of symbiotic nitrogen fixation has proven elusive.

Sign in / Sign up

Export Citation Format

Share Document