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Genes Mar 2020Rhizobia, the nitrogen-fixing symbionts of legumes, are polyphyletic bacteria distributed in many alpha- and beta-proteobacterial genera. They likely emerged and... (Review)
Review
Rhizobia, the nitrogen-fixing symbionts of legumes, are polyphyletic bacteria distributed in many alpha- and beta-proteobacterial genera. They likely emerged and diversified through independent horizontal transfers of key symbiotic genes. To replay the evolution of a new rhizobium genus under laboratory conditions, the symbiotic plasmid of was introduced in the plant pathogen , and the generated proto-rhizobium was submitted to repeated inoculations to the host, L. This experiment validated a two-step evolutionary scenario of key symbiotic gene acquisition followed by genome remodeling under plant selection. Nodulation and nodule cell infection were obtained and optimized mainly via the rewiring of regulatory circuits of the recipient bacterium. Symbiotic adaptation was shown to be accelerated by the activity of a mutagenesis cassette conserved in most rhizobia. Investigating mutated genes led us to identify new components of virulence and symbiosis. Nitrogen fixation was not acquired in our short experiment. However, we showed that post-infection sanctions allowed the increase in frequency of nitrogen-fixing variants among a non-fixing population in the system and likely allowed the spread of this trait in natura. Experimental evolution thus provided new insights into rhizobium biology and evolution.
Topics: Evolution, Molecular; Fabaceae; Rhizobium; Selection, Genetic; Symbiosis
PubMed: 32210028
DOI: 10.3390/genes11030339 -
Canadian Journal of Microbiology Jan 2019The rhizobium-legume symbiosis is a major source of fixed nitrogen (ammonia) in the biosphere. The potential for this process to increase agricultural yield while... (Review)
Review
The rhizobium-legume symbiosis is a major source of fixed nitrogen (ammonia) in the biosphere. The potential for this process to increase agricultural yield while reducing the reliance on nitrogen-based fertilizers has generated interest in understanding and manipulating this process. For decades, rhizobium research has benefited from the use of leading techniques from a very broad set of fields, including population genetics, molecular genetics, genomics, and systems biology. In this review, we summarize many of the research strategies that have been employed in the study of rhizobia and the unique knowledge gained from these diverse tools, with a focus on genome- and systems-level approaches. We then describe ongoing synthetic biology approaches aimed at improving existing symbioses or engineering completely new symbiotic interactions. The review concludes with our perspective of the future directions and challenges of the field, with an emphasis on how the application of a multidisciplinary approach and the development of new methods will be necessary to ensure successful biotechnological manipulation of the symbiosis.
Topics: Fabaceae; Gene Expression Profiling; Nitrogen Fixation; Rhizobium; Symbiosis
PubMed: 30205015
DOI: 10.1139/cjm-2018-0377 -
Applied and Environmental Microbiology Mar 2022The discovery of new and efficient genetic engineering technologies for will broaden the capacity for fundamental research on this genus and its utilization as a...
The discovery of new and efficient genetic engineering technologies for will broaden the capacity for fundamental research on this genus and its utilization as a transgenic vehicle. In this study, we aim to develop an efficient recombineering system for species. We examined isolates of and the closely related genus to identify pairs of ET-like recombinases that would aid in the recombineering of species. Four pairs of ET-like recombinases, named RecETh1h2h3h4, RecETh1h2P3, RecET, and RecETh, were identified in Agrobacterium tumefaciens strain B6, Rhizobium leguminosarum bv. trifolii WSM597, sp. strain LC145, and sp. strain Root483D2, respectively. Eight more candidate recombineering systems were generated by combining the new ET-like recombinases with Redγ or Pluγ. The PluγET system, the RecETh1h2h3h4 system, and the PluγETh system were determined to be the most efficient recombineering systems for the type strains A. tumefaciens C58, A. tumefaciens EHA105, and Rhizobium rhizogenes NBRC 13257, respectively. The utility of these systems was demonstrated by knocking out the - fusion gene in C58, the gene in EHA105, and the 3'-to-5' exonuclease gene and endoglucanase gene in NBRC 13257. Our work provides an effective genetic manipulation strategy for species. is a powerful transgenic vehicle for the genetic manipulation of numerous plant and fungal species and even animal cells. In addition to improving the utility of as a transgenic vehicle, genetic engineering tools are important for revealing crucial components that are functionally involved in transfer DNA (T-DNA) translocation events. This work developed an efficient and versatile recombineering system for . The successful genome modification of strains revealed that this new recombineering system could be used for the genetic engineering of .
Topics: Agrobacterium tumefaciens; Genetic Engineering; Recombinases; Rhizobium; Rhizobium leguminosarum
PubMed: 35044833
DOI: 10.1128/aem.02499-21 -
International Journal of Molecular... Aug 2020Nitrogen is essential for the growth of plants. The ability of some plant species to obtain all or part of their requirement for nitrogen by interacting with microbial... (Review)
Review
Nitrogen is essential for the growth of plants. The ability of some plant species to obtain all or part of their requirement for nitrogen by interacting with microbial symbionts has conferred a major competitive advantage over those plants unable to do so. The function of certain flavonoids (a group of secondary metabolites produced by the plant phenylpropanoid pathway) within the process of biological nitrogen fixation carried out by spp. has been thoroughly researched. However, their significance to biological nitrogen fixation carried out during the actinorhizal and arbuscular mycorrhiza-Rhizobium-legume interaction remains unclear. This review catalogs and contextualizes the role of flavonoids in the three major types of root endosymbiosis responsible for biological nitrogen fixation. The importance of gaining an understanding of the molecular basis of endosymbiosis signaling, as well as the potential of and challenges facing modifying flavonoids either quantitatively and/or qualitatively are discussed, along with proposed strategies for both optimizing the process of nodulation and widening the plant species base, which can support nodulation.
Topics: Fabaceae; Flavonoids; Nitrogen Fixation; Rhizobium; Root Nodules, Plant
PubMed: 32824698
DOI: 10.3390/ijms21165926 -
Microbiological Reviews Mar 1995Rhizobium, Bradyrhizobium, and Azorhizobium species are able to elicit the formation of unique structures, called nodules, on the roots or stems of the leguminous host.... (Review)
Review
Rhizobium, Bradyrhizobium, and Azorhizobium species are able to elicit the formation of unique structures, called nodules, on the roots or stems of the leguminous host. In these nodules, the rhizobia convert atmospheric N2 into ammonia for the plant. To establish this symbiosis, signals are produced early in the interaction between plant and rhizobia and they elicit discrete responses by the two symbiotic partners. First, transcription of the bacterial nodulation (nod) genes is under control of the NodD regulatory protein, which is activated by specific plant signals, flavonoids, present in the root exudates. In return, the nod-encoded enzymes are involved in the synthesis and excretion of specific lipooligosaccharides, which are able to trigger on the host plant the organogenic program leading to the formation of nodules. An overview of the organization, regulation, and function of the nod genes and their participation in the determination of the host specificity is presented.
Topics: Base Sequence; Fabaceae; Genes, Bacterial; Microtubule Proteins; Molecular Sequence Data; Plants, Medicinal; Rhizobium; Symbiosis
PubMed: 7708010
DOI: 10.1128/mr.59.1.124-142.1995 -
International Journal of Molecular... Mar 2022Many molecular signals are exchanged between rhizobia and host legume plants, some of which are crucial for symbiosis to take place, while others are modifiers of the... (Review)
Review
Many molecular signals are exchanged between rhizobia and host legume plants, some of which are crucial for symbiosis to take place, while others are modifiers of the interaction, which have great importance in the competition with the soil microbiota and in the genotype-specific perception of host plants. Here, we review recent findings on strain-specific and host genotype-specific interactions between rhizobia and legumes, discussing the molecular actors (genes, gene products and metabolites) which play a role in the establishment of symbiosis, and highlighting the need for research including the other components of the soil (micro)biota, which could be crucial in developing rational-based strategies for bioinoculants and synthetic communities' assemblage.
Topics: Fabaceae; Nitrogen Fixation; Odorants; Rhizobium; Root Nodules, Plant; Soil; Symbiosis
PubMed: 35328782
DOI: 10.3390/ijms23063358 -
BioMed Research International 2018Most legume species have the ability to establish a symbiotic relationship with soil nitrogen-fixing rhizobacteria that promote plant growth and productivity. There is... (Review)
Review
Most legume species have the ability to establish a symbiotic relationship with soil nitrogen-fixing rhizobacteria that promote plant growth and productivity. There is an increasing evidence of reactive oxygen species (ROS) important role in formation of legume-rhizobium symbiosis and nodule functioning. Environmental pollutants such as chromium compounds can cause damage to rhizobia, legumes, and their symbiosis. In plants, toxic effects of chromium(VI) compounds are associated with the increased production of ROS and oxidative stress development as well as with inhibition of pigment synthesis and modification of virtually all cellular components. These metabolic changes result in inhibition of seed germination and seedling development as well as reduction of plant biomass and crop yield. However, if plants establish symbiosis with rhizobia, heavy metals are accumulated preferentially in nodules decreasing the toxicity of metals to the host plant. This review summarizes data on toxic effects of chromium on legume plants and legume-rhizobium symbiosis. In addition, we discussed the role of oxidative stress in both chromium toxicity and formation of rhizobial symbiosis and use of nodule bacteria for minimizing toxic effects of chromium on plants.
Topics: Chromium; Fabaceae; Free Radicals; Rhizobium; Symbiosis
PubMed: 29662899
DOI: 10.1155/2018/8031213 -
Cells Apr 2021The intracellular infection thread initiated in a root hair cell is a unique structure associated with -legume symbiosis. It is characterized by inverted tip growth of... (Review)
Review
The intracellular infection thread initiated in a root hair cell is a unique structure associated with -legume symbiosis. It is characterized by inverted tip growth of the plant cell wall, resulting in a tunnel that allows invasion of host cells by bacteria during the formation of the nitrogen-fixing root nodule. Regulation of the plant-microbial interface is essential for infection thread growth. This involves targeted deposition of the cell wall and extracellular matrix and tight control of cell wall remodeling. This review describes the potential role of different actors such as transcription factors, receptors, and enzymes in the rearrangement of the plant-microbial interface and control of polar infection thread growth. It also focuses on the composition of the main polymers of the infection thread wall and matrix and the participation of reactive oxygen species (ROS) in the development of the infection thread. Mutant analysis has helped to gain insight into the development of host defense reactions. The available data raise many new questions about the structure, function, and development of infection threads.
Topics: Fabaceae; Host-Pathogen Interactions; Rhizobium; Rhizosphere; Symbiosis
PubMed: 33946779
DOI: 10.3390/cells10051050 -
The Plant Cell 2002
Review
Topics: Fabaceae; Lipopolysaccharides; Plant Roots; Rhizobium; Signal Transduction
PubMed: 12045280
DOI: 10.1105/tpc.002451 -
Microbiological Research Nov 2016Rhizobia are a class of symbiotic diazotrophic bacteria which utilize C4 acids in preference to sugars and the sugar utilization is repressed as long as C4 acids are... (Review)
Review
Rhizobia are a class of symbiotic diazotrophic bacteria which utilize C4 acids in preference to sugars and the sugar utilization is repressed as long as C4 acids are present. This can be manifested as a diauxie when rhizobia are grown in the presence of a sugar and a C4 acid together. Succinate, a C4 acid is known to repress utilization of sugars, sugar alcohols, hydrocarbons, etc by a mechanism termed as Succinate Mediated Catabolite Repression (SMCR). Mechanism of catabolite repression determines the hierarchy of carbon source utilization in bacteria. Though the mechanism of catabolite repression has been well studied in model organisms like E. coli, B. subtilis and Pseudomonas sp., mechanism of SMCR in rhizobia has not been well elucidated. C4 acid uptake is important for effective symbioses while mutation in the sugar transport and utilization genes does not affect symbioses. Deletion of hpr and sma0113 resulted in the partial relief of SMCR of utilization of galactosides like lactose, raffinose and maltose in the presence of succinate. However, no such regulators governing SMCR of glucoside utilization have been identified till date. Though rhizobia can utilize multitude of sugars, high affinity transporters for many sugars are yet to be identified. Identifying high affinity sugar transporters and studying the mechanism of catabolite repression in rhizobia is important to understand the level of regulation of SMCR and the key regulators involved in SMCR.
Topics: Acids; Bacterial Proteins; Biological Transport; Carbohydrate Metabolism; Gene Expression Regulation, Bacterial; Metabolic Networks and Pathways; Mutation; Organic Chemicals; Rhizobium; Symbiosis
PubMed: 27664739
DOI: 10.1016/j.micres.2016.07.006