scholarly journals Rhizobial Synthesized Cytokinins Contribute to But Are Not Essential for the Symbiotic Interaction Between Photosynthetic Bradyrhizobia and Aeschynomene Legumes

2013 ◽  
Vol 26 (10) ◽  
pp. 1232-1238 ◽  
Author(s):  
Kateřina Podlešáková ◽  
Joel Fardoux ◽  
Delphine Patrel ◽  
Katia Bonaldi ◽  
Ondřej Novák ◽  
...  
Keyword(s):  
Root Nodules ◽  
Rna Degradation ◽  
Nodule Development ◽  
Nodule Formation ◽  
Symbiotic Interaction ◽  
Extracellular Medium ◽  
Exogenous Addition ◽  
Bradyrhizobium Sp ◽  
Derivatives Of

Cytokinins (CK) play an important role in the formation of nitrogen-fixing root nodules. It has been known for years that rhizobia secrete CK in the extracellular medium but whether they play a role in nodule formation is not known. We have examined this question using the photosynthetic Bradyrhizobium sp. strain ORS285 which is able to nodulate Aeschynomene afraspera and A. indica using a Nod-dependent or Nod-independent symbiotic process, respectively. CK profiling showed that the most abundant CK secreted by Bradyrhizobium sp. strain ORS285 are the 2MeS (2-methylthiol) derivatives of trans-zeatin and isopentenyladenine. In their pure form, these CK can activate legume CK receptors in vitro, and their exogenous addition induced nodule-like structures on host plants. Deletion of the miaA gene showed that transfer RNA degradation is the source of CK production in Bradyrhizobium sp. strain ORS285. In nodulation studies performed with A. indica and A. afraspera, the miaA mutant had a 1-day delay in nodulation and nitrogen fixation. Moreover, A. indica plants formed considerably smaller but more abundant nodules when inoculated with the miaA mutant. These data show that CK produced by Bradyrhizobium sp. strain ORS285 are not the key signal triggering nodule formation during the Nod-independent symbiosis but they contribute positively to nodule development in Aeschynomene plants.

scholarly journals A Convenient, Soil-Free Method for the Production of Root Nodules in Soybean to Study the Effects of Exogenous Additives

2018 ◽  
Author(s):  
Swarup Roy Choudhury ◽  
Sarah M. Johns ◽  
Sona Pandey
Keyword(s):  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Root Nodules ◽  
Growth Conditions ◽  
Nodule Development ◽  
Nodule Formation ◽  
Legume Crop ◽  
Simple Protocol ◽  
Biological Nitrogen

Legumes develop root nodules that harbour endosymbiotic bacteria, rhizobia. These rhizobia convert nitrogen to ammonia by biological nitrogen fixation. A thorough understanding of the biological nitrogen fixation in legumes and its regulation is key to develop sustainable agriculture. It is well known that plant hormones affect nodule formation; however, most studies are limited to model legumes due to their suitability for in vitro, plate-based assays. Specifically, it is almost impossible to measure the effects of exogenous hormones or other additives during nodule development in crop legumes such as soybean as they have huge root system in soil. To circumvent this issue, the present research develops suitable media and growth conditions for efficient nodule development under in vitro, soil free conditions in an important legume crop, soybean. Moreover, we also evaluate the effects of all major phytohormones during soybean nodulation under identical conditions. This versatile, inexpensive, scalable and simple protocol provides several advantages over previously established methods. It is extremely time-and resource-efficient, does not require special training or equipment, and produces highly reproducible results. The approach is expandable to other large legumes as well as for other exogenous additives.

scholarly journals Experimental evolution can enhance benefits of rhizobia to novel legume hosts

2021 ◽  
Vol 288 (1951) ◽  
pp. 20210812
Author(s):  
Kenjiro W. Quides ◽  
Alexandra J. Weisberg ◽  
Jerry Trinh ◽  
Fathi Salaheldine ◽  
Paola Cardenas ◽  
...  
Keyword(s):  
Root Nodules ◽  
Lotus Japonicus ◽  
Nodule Development ◽  
Nodule Formation ◽  
In Planta ◽  
Genetic Changes ◽  
Reduced Costs ◽  
Full Factorial ◽  
Host Tissues

Legumes preferentially associate with and reward beneficial rhizobia in root nodules, but the processes by which rhizobia evolve to provide benefits to novel hosts remain poorly understood. Using cycles of in planta and in vitro evolution, we experimentally simulated lifestyles where rhizobia repeatedly interact with novel plant genotypes with which they initially provide negligible benefits. Using a full-factorial replicated design, we independently evolved two rhizobia strains in associations with each of two Lotus japonicus genotypes that vary in regulation of nodule formation. We evaluated phenotypic evolution of rhizobia by quantifying fitness, growth effects and histological features on hosts, and molecular evolution via genome resequencing. Rhizobia evolved enhanced host benefits and caused changes in nodule development in one of the four host–symbiont combinations, that appeared to be driven by reduced costs during symbiosis, rather than increased nitrogen fixation. Descendant populations included genetic changes that could alter rhizobial infection or proliferation in host tissues, but lack of evidence for fixation of these mutations weakens the results. Evolution of enhanced rhizobial benefits occurred only in a subset of experiments, suggesting a role for host–symbiont genotype interactions in mediating the evolution of enhanced benefits from symbionts.

scholarly journals Isolation and evaluation of endophytic bacteria from root nodules of Glycine max L. (Merr.) and their potential use as biofertilizers

2019 ◽  
Vol 17 (3) ◽  
pp. e1103
Author(s):  
Arely A. Vargas-Díaz ◽  
Ronald Ferrera-Cerrato ◽  
Hilda V. Silva-Rojas ◽  
Alejandro Alarcón
Keyword(s):  
Endophytic Bacteria ◽  
Biochemical Characterization ◽  
Cropping Systems ◽  
Root Nodules ◽  
Nodule Development ◽  
Nodule Formation ◽  
N Fixation ◽  
Tropical Regions ◽  
Bradyrhizobium Sp ◽  
Soybean Plants

Aim of study: To isolate and characterize endophytic bacteria inhabiting soybean root nodules collected from two tropical cropping systems in Mexico, and to evaluate the bacterial effects in soybean plants under controlled conditions.Area of study: The study was carried out at two locations (San Antonio Cayal and Nuevo Progreso municipalities) of Campeche State, Mexico.Material and methods: Two experimental stages were performed: 1) isolation, morphological and biochemical characterization, and molecular identification of endophytic bacteria from root-nodules of four soybean varieties grown at field conditions; and 2) evaluation of the effects of endophytic isolates on soybean growth and nodule development, and the effects of bacterial co-inoculation on soybean plants, under controlled conditions.Main results: Twenty-three endophytic bacteria were isolated from root nodules, and identified as Agrobacterium, Bradyrhizobium, Rhizobium, Ensifer, Massilia, Chryseobacterium, Enterobacter, Microbacterium, Serratia, and Xanthomonas. Under controlled conditions, Rhizobium sp. CPO4.13C or Agrobacterium tumefaciens CPO4.15C significantly increased the plant height (46% and 41%, respectively), whereas Bradyrhizobium sp. CPO4.24C promoted the nodule formation (36 nodules/plant). The co-inoculation of B. japonicum USDA110 and Bradyrhizobium sp. CPO4.24C enhanced plant growth, height (33.87 cm), root nodulation (69 nodules/plant) and N-fixation (3.10 µmol C2H4 h-1 plant-1) in comparison to the negative control.Research highlights:  Results suggest that the native Bradyrhizobium sp. CPO4.24C may be used as a biofertilizer directed to developing sustainable soybean cropping at tropical regions.

scholarly journals Taxonomically Different Co-Microsymbionts of a Relict Legume, Oxytropis popoviana, Have Complementary Sets of Symbiotic Genes and Together Increase the Efficiency of Plant Nodulation

2018 ◽  
Vol 31 (8) ◽  
pp. 833-841 ◽  
Author(s):  
Vera I. Safronova ◽  
Andrey A. Belimov ◽  
Anna L. Sazanova ◽  
Elizaveta R. Chirak ◽  
Alla V. Verkhozina ◽  
...  
Keyword(s):  
Root Nodules ◽  
Housekeeping Genes ◽  
Nodule Formation ◽  
Symbiotic Genes ◽  
Internal Transcribed Spacer Region ◽  
Bradyrhizobium Sp ◽  
The Common ◽  
Different Strains ◽  
Slow Growing ◽  
Fix Genes

Ten rhizobial strains were isolated from root nodules of a relict legume Oxytropis popoviana Peschkova. For identification of the isolates, sequencing of rrs, the internal transcribed spacer region, and housekeeping genes recA, glnII, and rpoB was used. Nine fast-growing isolates were Mesorhizobium-related; eight strains were identified as M. japonicum and one isolate belonged to M. kowhaii. The only slow-growing isolate was identified as a Bradyrhizobium sp. Two strains, M. japonicum Opo-242 and Bradyrhizobium sp. strain Opo-243, were isolated from the same nodule. Symbiotic genes of these isolates were searched throughout the whole-genome sequences. The common nodABC genes and other symbiotic genes required for plant nodulation and nitrogen fixation were present in the isolate Opo-242. Strain Opo-243 did not contain the principal nod, nif, and fix genes; however, five genes (nodP, nodQ, nifL, nolK, and noeL) affecting the specificity of plant-rhizobia interactions but absent in isolate Opo-242 were detected. Strain Opo-243 could not induce nodules but significantly accelerated the root nodule formation after coinoculation with isolate Opo-242. Thus, we demonstrated that taxonomically different strains of the archaic symbiotic system can be co-microsymbionts infecting the same nodule and promoting the nodulation process due to complementary sets of symbiotic genes.

Effect of rhizobia and soil nitrate on the establishment and functioning of the soybean symbiosis in the field

1984 ◽  
Vol 35 (2) ◽  
pp. 149 ◽  
Author(s):  
DF Herridge ◽  
RJ Roughley ◽  
J Brockwell
Keyword(s):  
Soil Depth ◽  
Root Nodules ◽  
Xylem Sap ◽  
Progressive Increase ◽  
Rhizobium Japonicum ◽  
Nodule Development ◽  
Initial Increase ◽  
Nodule Formation ◽  
Mineral N ◽  
Nodule Initiation

The symbiosis of the root-nodules of Bragg soybean [Glycine max (L.) Merrill] and the relative dependence of the plants on symbiotic and soil sources of N were evaluated in an experiment conducted on a vertisol which was high in organic- and mineral-N, free of Rhizobium japonicum, and where poor nodulation was characteristic of inoculated, new sowings. Effective inoculant containing R. japonicum strain CB 1809 was sprayed into the seed bed at three rates of application (10-fold intervals). Increasing rates of inoculant led to greater numbers of rhizobia in the rhizosphere and in the soil, and to improved nodulation. Uninoculated plants did not nodulate. High soil NO-3 (30 �g N/g, top 30 cm) did not prevent prompt, abundant colonization of rhizospheres by the bacteria from the inoculant, but nodule initiation was delayed and nodule development was retarded until 42 days after sowing. There was an acceleration in nodule formation and development between 42 and 62 days which coincided with a depletion of NO-3 from the top 60 cm of the soil profile. Nodulated and unnodulated soybeans took up NO-3 at similar times and rates to a soil depth of 90 cm; only unnodulated plants utilized soil NO-3 below 90 cm. Vacuum-extracted stem (xylem) exudate was sampled from plants throughout growth and analysed for nitrogenous solutes. The proportion of ureide-N relative to total-solutes-N in xylem sap was used as an index of symbiotic N2-fixation. The initial increase in concentrations of ureides coincided with the period of accelerated nodule formation and development between 42 and 62 days. Thereafter, there was a progressive increase in ureide concentrations in nodulated plants, and the levels were related to rate of inoculation, extent of nodulation, and to the decline in concentrations of soil NO-3. Ureide concentrations in unnodulated plants remained low throughout. The quantities of NO-3-N and �-NH2- N in xylem sap were not related to nodulation. The differences between treatments in terms of whole-plant N and grain N were less than predicted from the symbiotic parameters. This indicated that soybeans compensated for symbiotic deficiencies by more efficient exploitation of soil N and/or by more efficient redistribution of vegetative N into grain N, and that nodulation and soil NO-3 were interactive and complementary in meeting the N requirements of the crop.

Characterization ofndvD, the third gene involved in the synthesis of cyclic β-(13),(16)-D-glucans inBradyrhizobium japonicum

2002 ◽  
Vol 48 (11) ◽  
pp. 1008-1016 ◽  
Author(s):  
Rongji Chen ◽  
Arvind A Bhagwat ◽  
Robert Yaklich ◽  
Donald L Keister
Keyword(s):  
Gene Deletion ◽  
Transmembrane Domain ◽  
Nodule Development ◽  
Symbiotic Interaction ◽  
Reading Frame ◽  
New Gene ◽  
Conjugative Gene Transfer ◽  
Glucan Synthesis

Previously, we identified two genes in Bradyrhizobium japonicum (ndvB, ndvC) that are required for cyclic β-(1[Formula: see text]3),(1[Formula: see text]6)-D-glucan synthesis and successful symbiotic interaction with soybean (Glycine max). In this study, we report a new open reading frame (ORF1) located in the intergenic region between ndvB and ndvC, which is essential for β-glucan synthesis and effective nodulation of G. max. This new gene is designated ndvD (nodule development). The ndvD translation product has a predicted molecular mass of 26.4 kDa with one transmembrane domain. Genetic experiments involving gene deletion, Tn5 insertion, and gene complementation revealed that the mutation of ndvD generated pleiotropic phenotypes, including hypoosmotic sensitivity, reduced motility, and defects in conjugative gene transfer, in addition to symbiotic ineffectiveness. Although deficient in in vivo β-glucan synthesis, membrane preparations from the ndvD mutant synthesized neutral β-glucans in vitro. Therefore, ndvD does not appear to be a structural gene for β-glucan synthesis. Our hypothesis for the mechanism of β-(1[Formula: see text]3),(1[Formula: see text]6)-D-glucan synthesis is presented. Key Words: β-glucans,Bradyrhizobium, soybean, nitrogen fixation.

XV.—The Effect of Certain Factors on the Formation of Root Nodules on Pea Plants in Aseptic Culture

1949 ◽  
Vol 63 (3) ◽  
pp. 219-229 ◽  
Author(s):  
Moira P. McGonagle
Keyword(s):  
Nicotinic Acid ◽  
Root Nodules ◽  
Nodule Development ◽  
Nodule Formation ◽  
Root Cultures ◽  
Growth Substances ◽  
Aseptic Culture ◽  
Whole Plant ◽  
Rooting Medium ◽  
Whole Plants

The experiments described in the present paper were undertaken as the outcome of an investigation into the possibility of securing nodule formation on leguminous roots cultured separately from the shoots. During that investigation it soon became clear that experiments on whole plants were necessary, in order to test the effect, on the nodulation of the normal whole plant, of certain conditions under which nodulation of root cultures was being attempted. It is thought that these observations on whole plants, though ancillary to the main investigation (which is still in progress), are of sufficient interest to be published separately. The observations are concerned with the effect of the following conditions or treatments on nodule development in a particular variety of pea:—(a) Depriving the plant of light;(b) the presence of sucrose in the rooting medium;(c) the presence of nitrate in the rooting medium; and(d) the presence of certain accessory growth substances, viz. aneurin and nicotinic acid, in the rooting medium.

scholarly journals Minimal gene set from Sinorhizobium (Ensifer) meliloti pSymA required for efficient symbiosis with Medicago

2020 ◽  
Vol 118 (2) ◽  
pp. e2018015118
Author(s):  
Barney A. Geddes ◽  
Jason V. S. Kearsley ◽  
Jiarui Huang ◽  
Maryam Zamani ◽  
Zahed Muhammed ◽  
...  
Keyword(s):  
Root Nodules ◽  
Nodule Development ◽  
Nodule Formation ◽  
Protein Coding ◽  
Bacterial Gene ◽  
Gene Set ◽  
Background Strain ◽  
Genetic Components ◽  
Sustainable Agricultural Systems ◽  
Bacterial Genes

Reduction of N2 gas to ammonia in legume root nodules is a key component of sustainable agricultural systems. Root nodules are the result of a symbiosis between leguminous plants and bacteria called rhizobia. Both symbiotic partners play active roles in establishing successful symbiosis and nitrogen fixation: while root nodule development is mostly controlled by the plant, the rhizobia induce nodule formation, invade, and perform N2 fixation once inside the plant cells. Many bacterial genes involved in the rhizobia–legume symbiosis are known, and there is much interest in engineering the symbiosis to include major nonlegume crops such as corn, wheat, and rice. We sought to identify and combine a minimal bacterial gene complement necessary and sufficient for symbiosis. We analyzed a model rhizobium, Sinorhizobium (Ensifer) meliloti, using a background strain in which the 1.35-Mb symbiotic megaplasmid pSymA was removed. Three regions representing 162 kb of pSymA were sufficient to recover a complete N2-fixing symbiosis with alfalfa, and a targeted assembly of this gene complement achieved high levels of symbiotic N2 fixation. The resulting gene set contained just 58 of 1,290 pSymA protein-coding genes. To generate a platform for future synthetic manipulation, the minimal symbiotic genes were reorganized into three discrete nod, nif, and fix modules. These constructs will facilitate directed studies toward expanding the symbiosis to other plant partners. They also enable forward-type approaches to identifying genetic components that may not be essential for symbiosis, but which modulate the rhizobium’s competitiveness for nodulation and the effectiveness of particular rhizobia–plant symbioses.

scholarly journals Metabolite Profiles of Nodulated Alfalfa Plants Indicate That Distinct Stages of Nodule Organogenesis Are Accompanied by Global Physiological Adaptations

2006 ◽  
Vol 19 (9) ◽  
pp. 998-1013 ◽  
Author(s):  
Aiko Barsch ◽  
Verena Tellström ◽  
Thomas Patschkowski ◽  
Helge Küster ◽  
Karsten Niehaus
Keyword(s):  
Organic Acid ◽  
Host Plant ◽  
Developmental Stages ◽  
Root Nodules ◽  
Nitrogen Deficiency ◽  
Metabolic Changes ◽  
Nodule Formation ◽  
Control Mechanisms ◽  
Symbiotic Interaction ◽  
Metabolite Profiles

An effective symbiosis between Sinorhizobium meliloti and its host plant Medicago sativa is dependent on a balanced physiological interaction enabling the microsymbiont to fix atmospheric nitrogen. Maintenance of the symbiotic interaction is regulated by still poorly understood control mechanisms. A first step toward a better understanding of nodule metabolism was the determination of characteristic metabolites for alfalfa root nodules. Furthermore, nodules arrested at different developmental stages were analyzed in order to address metabolic changes induced during the progression of nodule formation. Metabolite profiles of bacteroid-free pseudonodule extracts indicated that early nodule developmental processes are accompanied by photosynthate translocation but no massive organic acid formation. To determine metabolic adaptations induced by the presence of nonfixing bacteroids, nodules induced by mutant S. meliloti strains lacking the nitrogenase protein were analyzed. The bacteroids are unable to provide ammonium to the host plant, which is metabolically reflected by reduced levels of characteristic amino acids involved in ammonium fixation. Elevated levels of starch and sugars in Fix¯ nodules provide strong evidence that plant sanctions preventing a transformation from a symbiotic to a potentially parasitic interaction are not strictly realized via photo-synthate supply. Instead, metabolic and gene expression data indicate that alfalfa plants react to nitrogen-fixation-deficient bacteroids with a decreased organic acid synthesis and an early induction of senescence. Noneffective symbiotic interactions resulting from plants nodulated by mutant rhizobia also are reflected in characteristic metabolic changes in leaves. These are typical for nitrogen deficiency, but also highlight metabolites potentially involved in sensing the N status.

Determinate development of nodule roots in actinomycete-induced root nodules of Myrica gale

1978 ◽  
Vol 56 (11) ◽  
pp. 1357-1364 ◽  
Author(s):  
John G. Torrey ◽  
Dale Callaham
Keyword(s):  
Root Development ◽  
Root Nodules ◽  
Cortical Cell ◽  
Gas Diffusion ◽  
Nodule Development ◽  
Nodule Formation ◽  
Low Oxygen ◽  
Cortical Cells ◽  
Continuous Growth ◽  
Myrica Gale

Young seedlings of Myrica gale L. grown in water culture were inoculated with a nodule suspension containing the effective actinomycete which induced root nodule formation. Nodule development was followed from initiation to nodule lobe formation and nodule root development using living materials and fixed nodules sectioned for light microscopy. After root hair infection and prenodule formation, three stages were observed: nodule lobe formation, a transition or arrested state, and nodule root development. The primary nodule lobe meristem originates endogenously and its formation involves pericycle, endodermis, and cortical cell derivatives. The lobe develops slowly to about 2 mm in length while the cortical cells are invaded by the actinomycete endophyte. After a period of arrest of variable duration, from a few days to several weeks, the nodule lobe meristem begins altered development, forming the elongate nodule root which undergoes slow but continuous growth to about 3- to 4-cm final length. New nodule lobe primordia are initiated endogenously at the base of existing nodules lobes, ultimately forming a cluster of nodule roots. Each nodule root, which elongates at about 0.1–1.0 mm per day, has a terminal apical meristem with reduced root cap formation and produces a modified root structure possessing an elaborate cortical intercellular space system and a reduced central cylinder. Nodule root growth is distinctive in that it shows strong negative geotropism. The endophyte is restricted to cortical cells of the nodule lobe and is totally absent from tissues of the nodule root. A probable role for nodule roots is to facilitate gas diffusion to the nitrogen-fixing endophyte site in the nodule lobe when nodules occur under conditions of low oxygen tension.

Sign in / Sign up

Export Citation Format

Share Document