scholarly journals Exopolysaccharides produced by the symbiotic nitrogen-fixing bacteria of leguminosae

2011 ◽  
Vol 35 (3) ◽  
pp. 657-671 ◽  
Author(s):  
Cleide Aparecida Bomfeti ◽  
Ligiane Aparecida Florentino ◽  
Ana Paula Guimarães ◽  
Patrícia Gomes Cardoso ◽  
Mário César Guerreiro ◽  
...  
Keyword(s):  
Crop Yields ◽  
Mechanical Stability ◽  
Environmental Stresses ◽  
Degree Of Polymerization ◽  
Nodule Development ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Chemical Structures ◽  
Infection Threads

The process of biological nitrogen fixation (BNF), performed by symbiotic nitrogen fixing bacteria with legume species, commonly known as α and β rhizobia, provides high sustainability for the ecosystems. Its management as a biotechnology is well succeeded for improving crop yields. A remarkable example of this success is the inoculation of Brazilian soybeans with Bradyrhizobium strains. Rhizobia produce a wide diversity of chemical structures of exopolysaccharides (EPS). Although the role of EPS is relatively well studied in the process of BNF, their economic and environmental potential is not yet explored. These EPS are mostly species-specific heteropolysaccharides, which can vary according to the composition of sugars, their linkages in a single subunit, the repeating unit size and the degree of polymerization. Studies have showed that the EPS produced by rhizobia play an important role in the invasion process, infection threads formation, bacteroid and nodule development and plant defense response. These EPS also confer protection to these bacteria when exposed to environmental stresses. In general, strains of rhizobia that produce greater amounts of EPS are more tolerant to adverse conditions when compared with strains that produce less. Moreover, it is known that the EPS produced by microorganisms are widely used in various industrial activities. These compounds, also called biopolymers, provide a valid alternative for the commonly used in food industry through the development of products with identical properties or with better rheological characteristics, which can be used for new applications. The microbial EPS are also able to increase the adhesion of soil particles favoring the mechanical stability of aggregates, increasing levels of water retention and air flows in this environment. Due to the importance of EPS, in this review we discuss the role of these compounds in the process of BNF, in the adaptation of rhizobia to environmental stresses and in the process of soil aggregation. The possible applications of these biopolymers in industry are also discussed.

scholarly journals Characterization and ecological role of free-living nitrogen-fixing bacteria isolated from the rhizoplane of Melastoma malabathricum inhabiting acidic plain lands in Kalimantan

Tropics ◽  
2006 ◽  
Vol 15 (4) ◽  
pp. 365-369 ◽  
Author(s):  
Yasuyuki HASHIDOKO ◽  
Yukako GOTOU ◽  
Mitsuru OSAKI ◽  
Erry PURNOMO ◽  
Limin H. SUWIDO ◽  
...  
Keyword(s):  
Ecological Role ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Free Living ◽  
Melastoma Malabathricum

scholarly journals NO Network for Plant–Microbe Communication Underground: A Review

2021 ◽  
Vol 12 ◽  
Author(s):  
Anjali Pande ◽  
Bong-Gyu Mun ◽  
Da-Sol Lee ◽  
Murtaza Khan ◽  
Geun-Mo Lee ◽  
...  
Keyword(s):  
Mycorrhizal Fungi ◽  
Nodule Development ◽  
Symbiotic Interaction ◽  
Plant Microbe Interaction ◽  
Nodule Senescence ◽  
Infection Threads ◽  
Molecular Patterns ◽  
Defense Studies ◽  
Hair Curling

Mechanisms governing plant–microbe interaction in the rhizosphere attracted a lot of investigative attention in the last decade. The rhizosphere is not simply a source of nutrients and support for the plants; it is rather an ecosystem teeming with diverse flora and fauna including different groups of microbes that are useful as well as harmful for the plants. Plant–microbe interaction occurs via a highly complex communication network that involves sophisticated machinery for the recognition of friend and foe at both sides. On the other hand, nitric oxide (NO) is a key, signaling molecule involved in plant development and defense. Studies on legume–rhizobia symbiosis suggest the involvement of NO during recognition, root hair curling, development of infection threads, nodule development, and nodule senescence. A similar role of NO is also suggested in the case of plant interaction with the mycorrhizal fungi. Another, insight into the plant–microbe interaction in the rhizosphere comes from the recognition of pathogen-associated molecular patterns (PAMPs)/microbe-associated molecular patterns (MAMPs) by the host plant and thereby NO-mediated activation of the defense signaling cascade. Thus, NO plays a major role in mediating the communication between plants and microbes in the rhizosphere. Interestingly, reports suggesting the role of silicon in increasing the number of nodules, enhancing nitrogen fixation, and also the combined effect of silicon and NO may indicate a possibility of their interaction in mediating microbial communication underground. However, the exact role of NO in mediating plant–microbe interaction remains elusive. Therefore, understanding the role of NO in underground plant physiology is very important, especially in relation to the plant’s interaction with the rhizospheric microbiome. This will help devise new strategies for protection against phytopathogens and enhancing plant productivity by promoting symbiotic interaction. This review focuses on the role of NO in plant–microbe communication underground.

Uptake and Role of Molybdenum in Nitrogen-Fixing Bacteria

1977 ◽  
pp. 402-407
Author(s):  
PHILIP T. PIENKOS ◽  
VINOD K. SHAH ◽  
WINSTON J. BRILL
Keyword(s):  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria

CRISPR/Cas9 genome editing shows the important role of AZC_2928 gene in nitrogen-fixing bacteria of plants

2020 ◽  
Vol 20 (5) ◽  
pp. 657-668
Author(s):  
Xiaojing Wang ◽  
Sang Lv ◽  
Tao Liu ◽  
Jiale Wei ◽  
Shiyuan Qu ◽  
...  
Keyword(s):  
Genome Editing ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria

scholarly journals Phosphorylation systems in symbiotic nitrogen-fixing bacteria and their role in bacterial adaptation to various environmental stresses

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8466 ◽  
Author(s):  
Paulina Lipa ◽  
Monika Janczarek
Keyword(s):  
Environmental Changes ◽  
Current Knowledge ◽  
Environmental Stresses ◽  
Regulatory Mechanisms ◽  
Limiting Factors ◽  
Symbiotic Bacteria ◽  
Nodule Formation ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Regulatory Pathways

Symbiotic bacteria, commonly called rhizobia, lead a saprophytic lifestyle in the soil and form nitrogen-fixing nodules on legume roots. During their lifecycle, rhizobia have to adapt to different conditions prevailing in the soils and within host plants. To survive under these conditions, rhizobia fine-tune the regulatory machinery to respond rapidly and adequately to environmental changes. Symbiotic bacteria play an essential role in the soil environment from both ecological and economical point of view, since these bacteria provide Fabaceae plants (legumes) with large amounts of accessible nitrogen as a result of symbiotic interactions (i.e., rhizobia present within the nodule reduce atmospheric dinitrogen (N2) to ammonia, which can be utilized by plants). Because of its restricted availability in the soil, nitrogen is one of the most limiting factors for plant growth. In spite of its high content in the atmosphere, plants are not able to assimilate it directly in the N2 form. During symbiosis, rhizobia infect host root and trigger the development of specific plant organ, the nodule. The aim of root nodule formation is to ensure a microaerobic environment, which is essential for proper activity of nitrogenase, i.e., a key enzyme facilitating N2 fixation. To adapt to various lifestyles and environmental stresses, rhizobia have developed several regulatory mechanisms, e.g., reversible phosphorylation. This key mechanism regulates many processes in both prokaryotic and eukaryotic cells. In microorganisms, signal transduction includes two-component systems (TCSs), which involve membrane sensor histidine kinases (HKs) and cognate DNA-binding response regulators (RRs). Furthermore, regulatory mechanisms based on phosphoenolopyruvate-dependent phosphotranspherase systems (PTSs), as well as alternative regulatory pathways controlled by Hanks-type serine/threonine kinases (STKs) and serine/threonine phosphatases (STPs) play an important role in regulation of many cellular processes in both free-living bacteria and during symbiosis with the host plant (e.g., growth and cell division, envelope biogenesis, biofilm formation, response to stress conditions, and regulation of metabolism). In this review, we summarize the current knowledge of phosphorylation systems in symbiotic nitrogen-fixing bacteria, and their role in the physiology of rhizobial cells and adaptation to various environmental conditions.

Role of microRNAs in the legume - rhizobium nitrogen fixing symbiosis

2019 ◽  
Author(s):  
◽  
Nhung Thi Huyen Hoang
Keyword(s):  
Transcription Factor ◽  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Nodule Development ◽  
Atmospheric Nitrogen ◽  
Ammonia Production ◽  
Nitrogen Fixing ◽  
Nodule Number ◽  
Biological Nitrogen

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] Nitrogen is a macronutrient that is critical for plant growth and development because it provides the building blocks of nucleic acids, proteins, chlorophyll, and energy- transfer compounds, such as ATP. Although 78% of the atmosphere is diatomic nitrogen, this form is inert and unavailable to plants due to the strong nitrogen-nitrogen triple bond. Plants can only absorb nitrogen in the forms of NH4+ or NO3-. Most of the inorganic nitrogen available to crop plants is provided through fertilizers synthesized based on the Haber-Bosch process. This process converts atmospheric nitrogen (N2) into ammonia (NH3) by a reaction with hydrogen (H2) using a metal catalyst (iron) under high temperatures (~500 [degrees]C) and high pressures (150-300 bar). Ammonia production by this method consumes a lot of energy, which is derived from burning fossil fuels. Synthetic ammonia production by the Haber-Bosch process causes losses of biodiversity through eutrophication, soil acidification and global increase in N2O atmospheric concentration, which is the third most significant greenhouse gas. An alternative approach to provide a sustainable nitrogen source to plants without causing such damage to the environment is through biological nitrogen fixation between legume species and Rhizobium bacteria. The symbiotic interaction between legume plants and rhizobia results in the formation of root nodules, specialized organs within which rhizobia convert atmospheric nitrogen into ammonia for plant consumption. In return, the legume host plants provide rhizobia with photosynthate as a carbon source for their growth. The legume - Rhizobium symbiosis is a sophisticated process that requires numerous regulators including the 20-24 nucleotide-long microRNAs which negatively regulate the expression of their target messenger RNAs. In my study, we provide two examples that demonstrate the significant role of microRNAs in the symbiotic interplay between soybean, an important legume crop, and rhizobia. In the first example, our results suggest that gma-miR319i functions as a positive regulator of nodule number during the soybean - Bradyrhizobium symbiosis by targeting the TCP33 transcription factor. Overexpression and CRISPR/cas9-mediated gene mutation of gma-miR319i increased and reduced nodule number after rhizobial inoculation, respectively. gma-miR319i and TCP33 showed an inverse expression pattern in different stages of nodule development. TCP33 modulated nodule development in a gma-miR319i dependent manner. The expression of gma-miR319i and TCP33 was differentially regulated in one soybean mutant line that exhibits a hypernodulation phenotype. In the second example, we further investigated the mechanism by which two identical microRNAs, gma-miR171o and gma-miR171q, function in modulating the spatial and temporal aspects of soybean nodulation. Although sharing the identical mature sequence, gma-miR171o and gma-miR171q genes are divergent and show unique, tissue-specific expression patterns. The expression levels of the two miRNAs are negatively correlated with that of their target genes. Ectopic expression of these miRNAs in transgenic hairy roots resulted in a significant reduction in nodule formation. Both gma-miR171o and gma-miR171q target members of the GRAS transcription factor superfamily, namely GmSCL-6 and GmNSP2. Besides those two above-mentioned examples, we were able to generate and characterize an enhancer trap insertional mutant of the NODULATION SIGNALING PATHWAY 2 (NSP2) gene which is the target gene of Gma-miR171 and also an important regulator of nodulation. Overall, our study shows the importance of microRNAs in the regulation of nitrogen-fixing symbiosis. Our results contribute to efforts to fully understand the molecular mechanisms controlling the legume - Rhizobium interaction. Our ultimate hope is that the information gained through my studies can lead to an increased utilization of biological nitrogen fixation for sustainable agriculture and environment protection.

scholarly journals The Lotus japonicus ROP3 Is Involved in the Establishment of the Nitrogen-Fixing Symbiosis but Not of the Arbuscular Mycorrhizal Symbiosis

2021 ◽  
Vol 12 ◽  
Author(s):  
Ivette García-Soto ◽  
Raphael Boussageon ◽  
Yareni Marlene Cruz-Farfán ◽  
Jesus Daniel Castro-Chilpa ◽  
Liz Xochiquetzal Hernández-Cerezo ◽  
...  
Keyword(s):  
Root Colonization ◽  
Lotus Japonicus ◽  
Arbuscular Mycorrhizal ◽  
Arbuscular Mycorrhizal Symbiosis ◽  
Mycorrhizal Symbiosis ◽  
Nitrogen Fixing ◽  
Infection Threads ◽  
Root Symbioses ◽  
Specific Pathway

Legumes form root mutualistic symbioses with some soil microbes promoting their growth, rhizobia, and arbuscular mycorrhizal fungi (AMF). A conserved set of plant proteins rules the transduction of symbiotic signals from rhizobia and AMF in a so-called common symbiotic signaling pathway (CSSP). Despite considerable efforts and advances over the past 20 years, there are still key elements to be discovered about the establishment of these root symbioses. Rhizobia and AMF root colonization are possible after a deep cell reorganization. In the interaction between the model legume Lotus japonicus and Mesorhizobium loti, this reorganization has been shown to be dependent on a SCAR/Wave-like signaling module, including Rho-GTPase (ROP in plants). Here, we studied the potential role of ROP3 in the nitrogen-fixing symbiosis (NFS) as well as in the arbuscular mycorrhizal symbiosis (AMS). We performed a detailed phenotypic study on the effects of the loss of a single ROP on the establishment of both root symbioses. Moreover, we evaluated the expression of key genes related to CSSP and to the rhizobial-specific pathway. Under our experimental conditions, rop3 mutant showed less nodule formation at 7- and 21-days post inoculation as well as less microcolonies and a higher frequency of epidermal infection threads. However, AMF root colonization was not affected. These results suggest a role of ROP3 as a positive regulator of infection thread formation and nodulation in L. japonicus. In addition, CSSP gene expression was neither affected in NFS nor in AMS condition in rop3 mutant. whereas the expression level of some genes belonging to the rhizobial-specific pathway, like RACK1, decreased in the NFS. In conclusion, ROP3 appears to be involved in the NFS, but is neither required for intra-radical growth of AMF nor arbuscule formation.

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