Enhancing Rhizobium–Legume Symbiosis Using Signaling Factors

One of the most important signal transduction pathways in bacteria, quorum sensing, is involved in many regulatory circuits in rhizobia, especially in the control of communication between rhizobia and their plant hosts. In this study, we identified 3 autoinducer synthase genes — mrlI1, mrlI2, and mrlI3 — in Mesorhizobium loti NZP 2213. We found that MrlI1 and MrlI2 could synthesize distinct N-acyl homoserine lactone (AHL) autoinducers in rich medium cultures, and the expression of mrlI1 was shown to be growth-phase-dependent. MrlI3 did not produce any detectable AHL molecules under the culture conditions tested. To investigate whether these AHL synthases affect nodulation, we examined the nodulation of AHL-deficient mutants on their native plant host Lotus corniculatus and found that the efficiency of nodulation of bacteria with mutations of any of these 3 synthase genes was reduced, suggesting that quorum sensing systems in M. loti may play an important role in successful establishment of rhizobium–legume symbiosis.

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Panothenic Acid and the Nodule Bacteria-Legume Symbiosis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.21.6.301 ◽

1935 ◽

Vol 21 (6) ◽

pp. 301-304 ◽

Cited By ~ 17

Author(s):

C. H. McBurney ◽

W. B. Bollen ◽

R. J. Williams

Keyword(s):

Nodule Bacteria ◽

Legume Symbiosis

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Interactions of lectins and their saccharide receptors in theRhizobium-legume symbiosis

The Journal of Membrane Biology ◽

10.1007/bf01870336 ◽

1983 ◽

Vol 73 (1) ◽

pp. 1-16 ◽

Cited By ~ 53

Author(s):

Frank B. Dazzo ◽

Georges L. Truchet

Keyword(s):

Legume Symbiosis ◽

Saccharide Receptors

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Suppression of plant defence in rhizobia–legume symbiosis

Trends in Plant Science ◽

10.1016/s1360-1385(02)02336-1 ◽

2002 ◽

Vol 7 (10) ◽

pp. 440-444 ◽

Cited By ~ 93

Author(s):

Axel Mithöfer

Keyword(s):

Plant Defence ◽

Legume Symbiosis

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A Peptidoglycan-Remodeling Enzyme Is Critical for Bacteroid Differentiation in Bradyrhizobium spp. During Legume Symbiosis

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-03-16-0052-r ◽

2016 ◽

Vol 29 (6) ◽

pp. 447-457 ◽

Cited By ~ 17

Author(s):

Djamel Gully ◽

Daniel Gargani ◽

Katia Bonaldi ◽

Cédric Grangeteau ◽

Clémence Chaintreuil ◽

...

Keyword(s):

Immune Responses ◽

Essential Role ◽

Morphological Changes ◽

Large Fraction ◽

Morphological Differentiation ◽

Capsular Polysaccharides ◽

Cell Enlargement ◽

Legume Symbiosis ◽

Bradyrhizobium Spp ◽

Peptidoglycan Layer

In response to the presence of compatible rhizobium bacteria, legumes form symbiotic organs called nodules on their roots. These nodules house nitrogen-fixing bacteroids that are a differentiated form of the rhizobium bacteria. In some legumes, the bacteroid differentiation comprises a dramatic cell enlargement, polyploidization, and other morphological changes. Here, we demonstrate that a peptidoglycan-modifying enzyme in Bradyrhizobium strains, a DD-carboxypeptidase that contains a peptidoglycan-binding SPOR domain, is essential for normal bacteroid differentiation in Aeschynomene species. The corresponding mutants formed bacteroids that are malformed and hypertrophied. However, in soybean, a plant that does not induce morphological differentiation of its symbiont, the mutation does not affect the bacteroids. Remarkably, the mutation also leads to necrosis in a large fraction of the Aeschynomene nodules, indicating that a normally formed peptidoglycan layer is essential for avoiding the induction of plant immune responses by the invading bacteria. In addition to exopolysaccharides, capsular polysaccharides, and lipopolysaccharides, whose role during symbiosis is well defined, our work demonstrates an essential role in symbiosis for yet another rhizobial envelope component, the peptidoglycan layer.

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Symbiotic capability of calopo rhizobia from an agrisoil with different crops in Pernambuco

Revista Brasileira de Ciência do Solo ◽

10.1590/s0100-06832013000400005 ◽

2013 ◽

Vol 37 (4) ◽

pp. 869-876 ◽

Cited By ~ 4

Author(s):

Altanys Silva Calheiros ◽

Mario de Andrade Lira Junior ◽

Débora Magalhães Soares ◽

Márcia do Vale Barreto Figueiredo

Keyword(s):

Dry Matter ◽

Nitrogen Sources ◽

Dry Weight ◽

Dry Forest ◽

Forest Zone ◽

Symbiotic Efficiency ◽

Total N ◽

Calopogonium Mucunoides ◽

Legume Symbiosis ◽

Biological Nitrogen

Biological nitrogen fixation by rhizobium-legume symbiosis represents one of the most important nitrogen sources for plants and depends strongly on the symbiotic efficiency of the rhizobium strain. This study evaluated the symbiotic capacity of rhizobial isolates from calopo (CALOPOGONIUM MUCUNOIDES) taken from an agrisoil under BRACHIARIA DECUMBENS pasture, sabiá (MIMOSA CAESALPINIIFOLIA) plantations and Atlantic Forest areas of the Dry Forest Zone of Pernambuco. A total of 1,575 isolates were obtained from 398 groups. A single random isolate of each group was authenticated, in randomized blocks with two replications. Each plant was inoculated with 1 mL of a bacterial broth, containing an estimated population of 10(8) rhizobial cells mL-1. Forty-five days after inoculation, the plants were harvested, separated into shoots, roots and nodules, oven-dried to constant mass, and weighed. Next, the symbiotic capability was tested with 1.5 kg of an autoclaved sand:vermiculite (1:1) mixture in polyethylene bags. The treatments consisted of 122 authenticated isolates, selected based on the shoot dry matter, five uninoculated controls (treated with 0, 50, 100, 150, or 200 kg ha-1 N) and a control inoculated with SEMIA 6152 (=BR1602), a strain of BRADYRHIZOBIUM JAPONICUM The test was performed as described above. The shoot dry matter of the plants inoculated with the most effective isolates did not differ from that of plants treated with 150 kg ha-1 N. Shoot dry matter was positively correlated with all other variables. The proportion of effective isolates was highest among isolates from SABIÁ forests. There was great variation in nodule dry weight, as well as in N contents and total N.

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Biotechnological approaches to develop nitrogen-fixing cereals: A review

Spanish Journal of Agricultural Research ◽

10.5424/sjar/2021194-18346 ◽

2021 ◽

Vol 19 (4) ◽

pp. e08R01-e08R01

Author(s):

Asma Boujenna ◽

Keyword(s):

Cereal Crops ◽

N Fixation ◽

N Availability ◽

Environmental Consequences ◽

Industrialized Nations ◽

Oxygen Sensitive ◽

Legume Symbiosis ◽

Living Organisms ◽

Agricultural Yields ◽

Biological Nitrogen

Agricultural yields are often limited by nitrogen (N) availability, especially in countries of the developing world, whereas in industrialized nations the application of chemical N fertilizers has reached unsustainable levels that have resulted in severe environmental consequences. Finding alternatives to inorganic fertilizers is critical for sustainable and secure food production. Although gaseous nitrogen (N2) is abundant in the atmosphere, it cannot be assimilated by most living organisms. Only a selected group of microorganisms termed diazotrophs, have evolved the ability to reduce N2 to generate NH3 in a process known as biological nitrogen fixation (BNF) catalysed by nitrogenase, an oxygen-sensitive enzyme complex. This ability presents an opportunity to improve the nutrition of crop plants, through the introduction into cereal crops of either the N fixing bacteria or the nitrogenase enzyme responsible for N fixation. This review explores three potential approaches to obtain N-fixing cereals: (a) engineering the nitrogenase enzyme to function in plant cells; (b) engineering the legume symbiosis into cereals; and (c) engineering cereals with the capability to associate with N-fixing bacteria.

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