symbifix
476 views | +0 today
Follow
Your new post is loading...
Your new post is loading...
Scooped by Symbifix Network
Scoop.it!

SYMBIFIX Network - Nitrogen-fixing root symbioses: from legumes to cereals

SYMBIFIX Network - Nitrogen-fixing root symbioses: from legumes to cereals | symbifix | Scoop.it
Objectives of the NetworkTo promote communication and the exchange of ideas and materials between and within the community of biologists specializing in symbiotic nitrogen fixation and the community specializing in cereals (plant biologists and microbiologists).To promote the emergence of tools, approaches and experimental models, in particular for developing strategies for the bioengineering of «nitrogen-fixing cereals».To prepare to respond to calls for proposals (ANR, Europe, International) and to promote the setting up of joint propositions.To increase the visibility and the dynamism of French research on nitrogen-fixing symbioses and the potential transfer to cereals.To increase the attractivity of the subject to French and foreign students and young researchers.
No comment yet.
Scooped by Symbifix Network
Scoop.it!

Program - 4th meeting on Molecular Mechanisms in Nitrogen-Fixing Root Endosymbioses

Program - 4th meeting on Molecular Mechanisms in Nitrogen-Fixing Root Endosymbioses | symbifix | Scoop.it

4th meeting on Molecular Mechanisms in Nitrogen-Fixing Root Endosymbioses will be held in Nice, 29-30 October 2015.

Session 1. Early signalling and infection

Session 2. Regulation of nodulation

Session 3. New insights from Omics studies

Session 4. Adaptation and evolution

No comment yet.
Scooped by Symbifix Network
Scoop.it!

Robust biological nitrogen fixation in a model grass–bacterial association - Pankievicz - 2015 - The Plant Journal - Wiley Online Library

Robust biological nitrogen fixation in a model grass–bacterial association - Pankievicz - 2015 - The Plant Journal - Wiley Online Library | symbifix | Scoop.it
Symbifix Networks insight:

Nitrogen-fixing rhizobacteria can promote plant growth; however, it is controversial whether biological nitrogen fixation (BNF) from associative interaction contributes to growth promotion. The roots of Setaria viridis, a model C4 grass, were effectively colonized by bacterial inoculants resulting in a significant enhancement of growth. Nitrogen-13 tracer studies provided direct evidence for tracer uptake by the host plant and incorporation into protein. Indeed, plants showed robust growth under nitrogen-limiting conditions when inoculated with an ammonium-excreting strain of Azospirillum brasilense. 11C-labeling experiments showed that patterns in central carbon metabolism and resource allocation exhibited by nitrogen-starved plants were largely reversed by bacterial inoculation, such that they resembled plants grown under nitrogen-sufficient conditions. Adoption of S. viridis as a model should promote research into the mechanisms of associative nitrogen fixation with the ultimate goal of greater adoption of BNF for sustainable crop production.

No comment yet.
Rescooped by Symbifix Network from Symbiosis & Evolution
Scoop.it!

Transcriptomic analysis of Sinorhizobium meliloti and Medicago truncatula symbiosis using nitrogen fixation deficient nodules

Transcriptomic analysis of Sinorhizobium meliloti and Medicago truncatula symbiosis using nitrogen fixation deficient nodules | symbifix | Scoop.it
The bacterium Sinorhizobium meliloti interacts symbiotically with legume plant hosts such as Medicago truncatula to form nitrogen-fixing root nodules. During symbiosis, plant and bacterial cells differentiate in a coordinated manner, resulting in specialized plant cells that contain nitrogen-fixing bacteroids. Both plant and bacterial genes are required at each developmental stage of symbiosis. We analyzed gene expression in nodules formed by wild type bacteria on six plant mutants with defects in nitrogen fixation (dnf). We observed differential expression of 482 S. meliloti genes with functions in cell envelope homeostasis, cell division, stress response, energy metabolism and nitrogen fixation. We simultaneously analyzed gene expression in M. truncatula and observed differential regulation of host processes that may trigger bacteroid differentiation and control bacterial infection. Our analyses of developmentally arrested plant mutants indicate that plants use distinct means to control bacterial infection during early and late symbiotic stages.

Via Chang Fu Tian
No comment yet.
Scooped by Symbifix Network
Scoop.it!

Medicago truncatula symbiosis mutants affected in the interaction with a biotrophic root pathogen - Rey - 2014 - New Phytologist - Wiley Online Library

Medicago truncatula symbiosis mutants affected in the interaction with a biotrophic root pathogen - Rey - 2014 - New Phytologist - Wiley Online Library | symbifix | Scoop.it
Symbifix Networks insight:

Understanding how plants balance between enabling microbial symbionts and fending off pathogens has direct implications both for basic plant biology and optimal use of crop plants in agriculture. The degree to which the processes associated with these two types of interactions overlap is poorly known. Recent studies revealed that symbiotic and pathogenic filamentous microbes require common plant genetic elements to establish colonization (Wang et al., 2012; Rey et al., 2013), supporting the long-held view that plants have evolved the ability to accommodate microbes (Parniske, 2000) and that pathogens have exploited these pathways. However, the extent to which plant genes implicated in fungal or bacterial symbioses are involved in interactions with biotrophic pathogens is unknown and research has been hampered by the lack of suitable common host experimental systems.

No comment yet.
Rescooped by Symbifix Network from Plant-Microbe Symbiosis
Scoop.it!

Primary transcripts of microRNAs encode regulatory peptides : Nature : Nature Publishing Group

Primary transcripts of microRNAs encode regulatory peptides : Nature : Nature Publishing Group | symbifix | Scoop.it
MicroRNAs (miRNAs) are small regulatory RNA molecules that inhibit the expression of specific target genes by binding to and cleaving their messenger RNAs or otherwise inhibiting their translation into proteins1. miRNAs are transcribed as much larger primary transcripts (pri-miRNAs), the function of which is not fully understood. Here we show that plant pri-miRNAs contain short open reading frame sequences that encode regulatory peptides. The pri-miR171b of Medicago truncatula and the pri-miR165a of Arabidopsis thaliana produce peptides, which we term miPEP171b and miPEP165a, respectively, that enhance the accumulation of their corresponding mature miRNAs, resulting in downregulation of target genes involved in root development. The mechanism of miRNA-encoded peptide (miPEP) action involves increasing transcription of the pri-miRNA. Five other pri-miRNAs of A. thaliana and M. truncatula encode active miPEPs, suggesting that miPEPs are widespread throughout the plant kingdom. Synthetic miPEP171b and miPEP165a peptides applied to plants specifically trigger the accumulation of miR171b and miR165a, leading to reduction of lateral root development and stimulation of main root growth, respectively, suggesting that miPEPs might have agronomical applications.

Via Jean-Michel Ané
Jean-Michel Ané's curator insight, March 25, 2015 7:12 PM

Congrats Jean-Philippe!

Scooped by Symbifix Network
Scoop.it!

Rhizobium Lipo-Chitooligosaccharide Signaling Triggers Accumulation of Cytokinins in Medicago Truncatula Roots: Molecular Plant

Symbifix Networks insight:

The legume rhizobium symbiosis is initiated uponperception of bacterial secreted lipo-chito oligosaccharides (LCOs). Perception of these signals by the plant initiates a signalling cascade that leads to nodule formation. Several studies have implicated a function for cytokinin in this process. However, whether cytokinin accumulation and subsequent signalling are an integral part of rhizobium LCO signalling remains elusive. Here we show that cytokinin signalling is required for the majority of transcriptional changes induced by rhizobium LCOs. Additionally, we demonstrate that several cytokinins accumulate in the root susceptible zone three hours post rhizobium LCO application, including the biologically most active cytokinins trans-zeatin and isopentenyl adenine. These responses are dependent on CCaMK; a key protein in rhizobial LCO induced signalling. Analysis of the ethylene insensitive Mtein2/Mtsickle mutant showed that LCO-induced cytokinin accumulation is negatively regulated by ethylene. Together with transcriptional induction of ethylene biosynthesis genes, it suggests a feedback loop negatively regulating LCO signalling and subsequent cytokinin accumulation. We argue that cytokinin accumulation is a key step in the pathway leading to nodule organogenesis and that this is tightly controlled by feedback loops.

No comment yet.
Rescooped by Symbifix Network from Plant-Microbe Symbiosis
Scoop.it!

Symbiotic diversity, specificity and distribution of rhizobia in native legumes of the Core Cape Subregion (South Africa)

Symbiotic diversity, specificity and distribution of rhizobia in native legumes of the Core Cape Subregion (South Africa) | symbifix | Scoop.it
Rhizobial diversity and host preferences were assessed in 65 native Fynbos legumes of the papilionoid legume tribes Astragaleae, Crotalarieae, Genisteae, Indigofereae, Millettieae, Phaseoleae, Podalyrieae, Psoraleeae and Sesbanieae. Sequence analyses of chromosomal 16S rRNA, recA, atpD and symbiosis-related nodA, nifH genes in parallel with immunogold labelling assays identified the symbionts as alpha- (Azorhizobium, Bradyrhizobium, Ensifer, Mesorhizobium and Rhizobium) and beta-rhizobial (Burkholderia) lineages with the majority placed in the genera Mesorhizobium and Burkholderia showing a wide range of host interactions. Despite a degree of symbiotic promiscuity in the tribes Crotalarieae and Indigofereae nodulating with both alpha- and beta-rhizobia, Mesorhizobium symbionts appeared to exhibit a general host preference for the tribe Psoraleeae, whereas Burkholderia prevailed in the Podalyrieae. Although host genotype was the main factor determining rhizobial diversity, ecological factors such as soil acidity and site elevation were positively correlated with genetic variation within Mesorhizobium and Burkholderia, respectively, indicating an interplay of host and environmental factors on the distribution of Fynbos rhizobia.

Via Jean-Michel Ané
No comment yet.
Rescooped by Symbifix Network from Plant-Microbe Symbiosis
Scoop.it!

Nitric oxide: a multifaceted regulator of the nitrogen-fixing symbiosis

Nitric oxide: a multifaceted regulator of the nitrogen-fixing symbiosis | symbifix | Scoop.it
The specific interaction between legumes and Rhizobium-type bacteria leads to the establishment of a symbiotic relationship characterized by the formation of new differentiated organs named nodules, which provide a niche for bacterial nitrogen (N2) fixation. In the nodules, bacteria differentiate into bacteroids with the ability to fix atmospheric N2 via nitrogenase activity. As nitrogenase is strongly inhibited by oxygen, N2 fixation is made possible by the microaerophilic conditions prevailing in the nodules. Increasing evidence has shown the presence of NO during symbiosis, from early interaction steps between the plant and the bacterial partners to N2-fixing and senescence steps in mature nodules. Both the plant and the bacterial partners participate in NO synthesis. NO was found to be required for the optimal establishment of the symbiotic interaction. Transcriptomic analysis at an early stage of the symbiosis showed that NO is potentially involved in the repression of plant defence reactions, favouring the establishment of the plant–microbe interaction. In mature nodules, NO was shown to inhibit N2 fixation, but it was also demonstrated to have a regulatory role in nitrogen metabolism, to play a beneficial metabolic function for the maintenance of the energy status under hypoxic conditions, and to trigger nodule senescence. The present review provides an overview of NO sources and multifaceted effects from the early steps of the interaction to the senescence of the nodule, and presents several approaches which appear to be particularly promising in deciphering the roles of NO in N2-fixing symbioses.

Via Jean-Michel Ané
No comment yet.
Scooped by Symbifix Network
Scoop.it!

Structural basis for regulation of rhizobial nodulation and symbiosis gene expression by the regulatory protein NolR

Structural basis for regulation of rhizobial nodulation and symbiosis gene expression by the regulatory protein NolR | symbifix | Scoop.it

Nitrogen nodules formed by the symbiosis of rhizobial microbes and legume roots are essential for fixation of nitrogen in the environment. As part of the symbiosis that leads to nodule formation, a series of changes in gene expression of the Rhizobium must occur. The protein NolR is a global regulator of rhizobial genes for symbiosis and nodulation. Here, we describe the three-dimensional structure of this transcription factor in unliganded and DNA bound forms. These structures show how NolR recognizes asymmetric DNA binding sites and reveal a previously unknown mechanism for conformational switching that alters the energetics of interaction to accommodate variable DNA sequences. Two models for the role of NolR in the regulation of nodulation and symbiosis genes are also proposed.

No comment yet.
Scooped by Symbifix Network
Scoop.it!

Rhizobial peptidase HrrP cleaves host-encoded signaling peptides and mediates symbiotic compatibility

Rhizobial peptidase HrrP cleaves host-encoded signaling peptides and mediates symbiotic compatibility | symbifix | Scoop.it
Symbifix Networks insight:

The agriculturally important symbiosis between nitrogen-fixing bacteria (rhizobia) and their legume hosts occurs within root nodules. This partnership requires a molecular dialogue that ensures specificity and directs the codevelopment of the two organisms during nodule formation. This paper characterizes a protein, host range restriction peptidase (HrrP), which plays a role in this dialogue. Rhizobial strains that express HrrP tend to exhibit more parasitic properties, such as failing to provide fixed nitrogen for their hosts and proliferating more abundantly within nodule tissue. HrrP likely exhibits these properties by actively degrading plant-derived chemical signals that normally stimulate symbiotic cooperation.

No comment yet.
Scooped by Symbifix Network
Scoop.it!

Joint SymbiFix meeting & 4th meeting on Molecular Mechanisms in Nitrogen-Fixing Root Endosymbioses

Joint SymbiFix meeting & 4th meeting on Molecular Mechanisms in Nitrogen-Fixing Root Endosymbioses | symbifix | Scoop.it

Nice, 29-30 October 2015

The organizing committe: Pierre Frendo & Renaud Brouquisse

The scientific committee: Julie Cullimore, Catherine Masson-Boivin, Eric Giraud, Peter Mergaert, Philippe Normand, Pascal Gamas, Renaud Brouquisse, Pierre Frendo, Florian Frugier, Marc Lepetit

No comment yet.
Rescooped by Symbifix Network from Symbiosis & Evolution
Scoop.it!

Multiple steps control immunity during the intracellular accommodation of rhizobia

Multiple steps control immunity during the intracellular accommodation of rhizobia | symbifix | Scoop.it

Medicago truncatula belongs to the legume family and forms symbiotic associations with nitrogen fixing bacteria, the rhizobia. During these interactions, the plants develop root nodules in which bacteria invade the plant cells and fix nitrogen for the benefit of the plant. Despite massive infection, legume nodules do not develop visible defence reactions, suggesting a special immune status of these organs. Some factors influencing rhizobium maintenance within the plant cells have been previously identified, such as the M. truncatula NCR peptides whose toxic effects are reduced by the bacterial protein BacA. In addition, DNF2, SymCRK, and RSD are M. truncatula genes required to avoid rhizobial death within the symbiotic cells. DNF2 and SymCRK are essential to prevent defence-like reactions in nodules after bacteria internalization into the symbiotic cells. Herein, we used a combination of genetics, histology and molecular biology approaches to investigate the relationship between the factors preventing bacterial death in the nodule cells. We show that the RSD gene is also required to repress plant defences in nodules. Upon inoculation with the bacA mutant, defence responses are observed only in the dnf2 mutant and not in the symCRK and rsd mutants. In addition, our data suggest that lack of nitrogen fixation by the bacterial partner triggers bacterial death in nodule cells after bacteroid differentiation. Together our data indicate that, after internalization, at least four independent mechanisms prevent bacterial death in the plant cell. These mechanisms involve successively: DNF2, BacA, SymCRK/RSD and bacterial ability to fix nitrogen.


Via Chang Fu Tian
No comment yet.
Scooped by Symbifix Network
Scoop.it!

INRA - SymbiFix : un réseau scientifique sur la fixation symbiotique de l’azote

INRA - SymbiFix : un réseau scientifique sur la fixation symbiotique de l’azote | symbifix | Scoop.it
Le réseau SymbiFix a été mis en place par des chercheurs de différentes communautés scientifiques afin de développer des projets de recherche en commun et de favoriser les échanges. L’objectif principal du réseau est la compréhension du fonctionnement et de l’évolution des symbioses fixatrices d’azote.
Symbifix Networks insight:

Contact scientifique : Catherine MASSON, Laboratoire des Interactions Plantes Micro organismes (LIPM)

En savoir plus sur le réseau : http://www.fraib.fr/fraib/Divers/SYMBIFIX

No comment yet.
Rescooped by Symbifix Network from Plant-Microbe Symbiosis
Scoop.it!

Rhizobium Lipo-Chitooligosaccharide Signaling Triggers Accumulation of Cytokinins in Medicago Truncatula Roots

Rhizobium Lipo-Chitooligosaccharide Signaling Triggers Accumulation of Cytokinins in Medicago Truncatula Roots | symbifix | Scoop.it
Abstract

The legume rhizobium symbiosis is initiated uponperception of bacterial secreted lipo-chito oligosaccharides (LCOs). Perception of these signals by the plant initiates a signalling cascade that leads to nodule formation. Several studies have implicated a function for cytokinin in this process. However, whether cytokinin accumulation and subsequent signalling are an integral part of rhizobium LCO signalling remains elusive. Here we show that cytokinin signalling is required for the majority of transcriptional changes induced by rhizobium LCOs. Additionally, we demonstrate that several cytokinins accumulate in the root susceptible zone three hours post rhizobium LCO application, including the biologically most active cytokinins trans-zeatin and isopentenyl adenine. These responses are dependent on CCaMK; a key protein in rhizobial LCO induced signalling. Analysis of the ethylene insensitive Mtein2/Mtsickle mutant showed that LCO-induced cytokinin accumulation is negatively regulated by ethylene. Together with transcriptional induction of ethylene biosynthesis genes, it suggests a feedback loop negatively regulating LCO signalling and subsequent cytokinin accumulation. We argue that cytokinin accumulation is a key step in the pathway leading to nodule organogenesis and that this is tightly controlled by feedback loops.

Via Jean-Michel Ané
Rescooped by Symbifix Network from Plant-Microbe Symbiosis
Scoop.it!

Micromonospora from nitrogen fixing nodules of alfalfa (Medicago sativa L.). A new promising Plant Probiotic Bacteria.

Micromonospora from nitrogen fixing nodules of alfalfa (Medicago sativa L.). A new promising Plant Probiotic Bacteria. | symbifix | Scoop.it
Biotic interactions can improve agricultural productivity without costly and environmentally challenging inputs. Micromonospora strains have recently been reported as natural endophytes of legume nodules but their significance for plant development and productivity has not yet been established. The aim of this study was to determine the diversity and function of Micromonospora isolated from Medicago sativa root nodules. Micromonospora-like strains from field alfalfa nodules were characterized by BOX-PCR fingerprinting and 16S rRNA gene sequencing. The ecological role of the interaction of the 15 selected representative Micromonospora strains was tested in M. sativa. Nodulation, plant growth and nutrition parameters were analyzed. Alfalfa nodules naturally contain abundant and highly diverse populations of Micromonospora, both at the intra- and at interspecific level. Selected Micromonospora isolates significantly increase the nodulation of alfalfa by Ensifer meliloti 1021 and also the efficiency of the plant for nitrogen nutrition. Moreover, they promote aerial growth, the shoot-to-root ratio, and raise the level of essential nutrients. Our results indicate that Micromonospora acts as a Rhizobia Helper Bacteria (RHB) agent and has probiotic effects, promoting plant growth and increasing nutrition efficiency. Its ecological role, biotechnological potential and advantages as a plant probiotic bacterium (PPB) are also discussed.

Via Jean-Michel Ané
No comment yet.
Scooped by Symbifix Network
Scoop.it!

Identification of microRNAs and their mRNA targets during soybean nodule development: functional analysis of the role of miR393j-3p in soybean nodulation - Yan - 2015 - New Phytologist - Wiley Onli...

Identification of microRNAs and their mRNA targets during soybean nodule development: functional analysis of the role of miR393j-3p in soybean nodulation - Yan - 2015 - New Phytologist - Wiley Onli... | symbifix | Scoop.it
Plant microRNAs (miRNAs) play important regulatory roles in a number of developmental processes. The present work investigated the roles of miRNAs during nodule development in the crop legume soybean (Glycine max).Fifteen soybean small RNA libraries were sequenced from different stages of nodule development, including young nodules, mature nodules and senescent nodules. In order to identify the regulatory targets of the miRNAs, five parallel analysis of RNA ends (PARE) libraries were also sequenced from the same stages of nodule development.Sequencing identified 284 miRNAs, including 178 novel soybean miRNAs. Analysis of miRNA abundance identified 139 miRNAs whose expression was significantly regulated during nodule development, including 12 miRNAs whose expression changed > 10-fold. Analysis of the PARE libraries identified 533 miRNA targets, including three nodulation-related genes and eight nodule-specific genes.miR393j-3p was selected for detailed analysis as its expression was significantly regulated during nodule formation, and it targeted a nodulin gene, Early Nodulin 93 (ENOD93). Strong, ectopic expression of miR393j-3p, as well as RNAi silencing of ENOD93 expression, significantly reduced nodule formation. The data indicate that miR393j-3p regulation of ENOD93 mRNA abundance is a key control point for soybean nodule formation.
Gary Stacey's curator insight, April 10, 2015 1:43 PM

recent paper from our lab

Scooped by Symbifix Network
Scoop.it!

Ribosomal frameshifting and dual-target antiactivation restrict quorum-sensing–activated transfer of a mobile genetic element

Ribosomal frameshifting and dual-target antiactivation restrict quorum-sensing–activated transfer of a mobile genetic element | symbifix | Scoop.it
Symbifix Networks insight:

Symbiosis islands are integrative and conjugative mobile genetic elements that convert nonsymbiotic rhizobia into nitrogen-fixing symbionts of leguminous plants. Excision of the Mesorhizobium loti symbiosis island ICEMlSymR7A is indirectly activated by quorum sensing through TraR-dependent activation of the excisionase gene rdfS. Here we show that a +1 programmed ribosomal frameshift (PRF) fuses the coding sequences of two TraR-activated genes, msi172 and msi171, producing an activator of rdfS expression named Frameshifted excision activator (FseA). Mass-spectrometry and mutational analyses indicated that the PRF occurred through +1 slippage of the tRNAphe from UUU to UUC within a conserved msi172-encoded motif. FseA activated rdfS expression in the absence of ICEMlSymR7A, suggesting that it directly activated rdfS transcription, despite being unrelated to any characterized DNA-binding proteins. Bacterial two-hybrid and gene-reporter assays demonstrated that FseA was also bound and inhibited by the ICEMlSymR7A-encoded quorum-sensing antiactivator QseM. Thus, activation of ICEMlSymR7A excision is counteracted by TraR antiactivation, ribosomal frameshifting, and FseA antiactivation. This robust suppression likely dampens the inherent biological noise present in the quorum-sensing autoinduction circuit and ensures that ICEMlSymR7A transfer only occurs in a subpopulation of cells in which both qseM expression is repressed and FseA is translated. The architecture of the ICEMlSymR7A transfer regulatory system provides an example of how a set of modular components have assembled through evolution to form a robust genetic toggle that regulates gene transcription and translation at both single-cell and cell-population levels.

No comment yet.
Rescooped by Symbifix Network from MycorWeb Plant-Microbe Interactions
Scoop.it!

A novel intracellular nitrogen-fixing symbiosis made by Ustilago maydis and Bacillus spp. - Ruiz-Herrera - 2015 - New Phytologist - Wiley Online Library

A novel intracellular nitrogen-fixing symbiosis made by Ustilago maydis and Bacillus spp. - Ruiz-Herrera - 2015 - New Phytologist - Wiley Online Library | symbifix | Scoop.it

We observed that the maize pathogenic fungus Ustilago maydis grew in nitrogen (N)-free media at a rate similar to that observed in media containing ammonium nitrate, suggesting that it was able to fix atmospheric N2. Because only prokaryotic organisms have the capacity to reduce N2, we entertained the possibility that U. maydis was associated with an intracellular bacterium.The presence of nitrogenase in the fungus was analyzed by acetylene reduction, and capacity to fix N2 by use of 15N2. Presence of an intracellular N2-fixing bacterium was analyzed by PCR amplification of bacterial 16S rRNA and nifH genes, and by microscopic observations.Nitrogenase activity and 15N incorporation into the cells proved that U. maydis fixed N2. Light and electron microscopy, and fluorescence in situ hybridization (FISH) experiments revealed the presence of intracellular bacteria related to Bacillus pumilus, as evidenced by sequencing of the PCR-amplified fragments.These observations reveal for the first time the existence of an endosymbiotic N2-fixing association involving a fungus and a bacterium.


Via Francis Martin
No comment yet.