scholarly journals Rhizobial Exopolysaccharides: Genetic Regulation of Their Synthesis and Relevance in Symbiosis with Legumes

2021 ◽  
Vol 22 (12) ◽  
pp. 6233
Author(s):  
Sebastián Acosta-Jurado ◽  
Francisco Fuentes-Romero ◽  
Jose-Enrique Ruiz-Sainz ◽  
Monika Janczarek ◽  
José-María Vinardell
Keyword(s):  
Genetic Regulation ◽  
Bacterial Invasion ◽  
Rhizobial Strain ◽  
Nod Factors ◽  
Root Infection ◽  
Symbiotic Interaction ◽  
Cell Association ◽  
Acidic Polysaccharides ◽  
Surface Polysaccharides ◽  
Complex Regulation

Rhizobia are soil proteobacteria able to engage in a nitrogen-fixing symbiotic interaction with legumes that involves the rhizobial infection of roots and the bacterial invasion of new organs formed by the plant in response to the presence of appropriate bacterial partners. This interaction relies on a complex molecular dialogue between both symbionts. Bacterial N-acetyl-glucosamine oligomers called Nod factors are indispensable in most cases for early steps of the symbiotic interaction. In addition, different rhizobial surface polysaccharides, such as exopolysaccharides (EPS), may also be symbiotically relevant. EPS are acidic polysaccharides located out of the cell with little or no cell association that carry out important roles both in free-life and in symbiosis. EPS production is very complexly modulated and, frequently, co-regulated with Nod factors, but the type of co-regulation varies depending on the rhizobial strain. Many studies point out a signalling role for EPS-derived oligosaccharides in root infection and nodule invasion but, in certain symbiotic couples, EPS can be dispensable for a successful interaction. In summary, the complex regulation of the production of rhizobial EPS varies in different rhizobia, and the relevance of this polysaccharide in symbiosis with legumes depends on the specific interacting couple.

scholarly journals Rhizobial Exopolysaccharides: Genetic Regulation of Their Synthesis and Relevance in Symbiosis With Legumes

2021 ◽  
Author(s):  
Sebastián Acosta-Jurado ◽  
Francisco Fuentes-Romero ◽  
Jose-Enrique Ruiz-Sainz ◽  
Monika Janczarek ◽  
José-María Vinardell
Keyword(s):  
Genetic Regulation ◽  
Bacterial Invasion ◽  
Rhizobial Strain ◽  
Nod Factors ◽  
Root Infection ◽  
Symbiotic Interaction ◽  
Cell Association ◽  
Surface Polysaccharides ◽  
Complex Regulation

Abstract: Rhizobia are soil proteobacteria able to engage in a nitrogen-fixing symbiotic interaction with legumes which involves root rhizobial infection and bacterial invasion of new organs formed by the plant in response to the presence of appropriate bacterial partners. This interaction relies on a complex molecular dialogue between both symbionts. Bacterial N-acetyl-glucosamine oligomers called Nod factors are indispensable in most cases for early steps of the symbiotic interaction. In addition, different rhizobial surface polysaccharides, such as exopolysaccharides (EPS), may also be symbiotically relevant. EPS are acidic polysaccharides located out of the cell with little or no cell association that carry out important roles both in free-life and in symbiosis. EPS production is very complexly modulated and, frequently, co-regulated with that of Nod factors, but the type of co-regulation varies depending on the rhizobial strain. Many studies point out a signalling role of EPS-derived oligosaccharides in root infection and nodule invasion but, in certain symbiotic couples, EPS can be dispensable for a successful interaction. In summary, the complex regulation of the production of rhizobial EPS varies in different rhizobia and the relevance of this polysaccharide in symbiosis with legumes depends on the specific interacting couple.

scholarly journals Roles for Azorhizobial Nod Factors and Surface Polysaccharides in Intercellular Invasion and Nodule Penetration, Respectively

1998 ◽  
Vol 11 (10) ◽  
pp. 999-1008 ◽  
Author(s):  
Wim D'Haeze ◽  
Mengsheng Gao ◽  
Riet De Rycke ◽  
Marc Van Montagu ◽  
Gilbert Engler ◽  
...  
Keyword(s):  
Infection Process ◽  
Nodule Development ◽  
Nod Factors ◽  
Symbiotic Interaction ◽  
Simultaneous Application ◽  
Infection Threads ◽  
Cortical Infection ◽  
Surface Polysaccharides ◽  
Altered Surface ◽  
Cortical Regions

In the symbiotic interaction between Azorhizobium caulinodans and Sesbania rostrata root and stem-borne nodules are formed. The bacteria enter the host via intercellular spaces at lateral or adventitious root bases and form infection pockets in outer cortical layers. Infection threads guide the bacteria to nodule primordia where plant cells are invaded. To identify bacterial functions that are required for this infection process, two mutants defective in nodulation were studied; one produced no Nod factors (nodA mutant), the other had altered surface polysaccharides (SPS) and induced the formation of pseudo-nodules. Bacteria were visualized with the help of a nodA-uidA reporter fusion that was functional during nodule development and in bacteroids. In contrast to the SPS mutant, nodA mutants were unable to colonize outer cortical regions. In mixed inoculations with both mutants, functional nodules were formed, the central tissue of which was occupied by the nodA mutant. These observations suggest that SPS play a role in deeper invasion and that Nod factors are necessary for entry. Simultaneous application of purified Nod factors and nodA mutant bacteria restored the formation of outer cortical infection pockets leading to the conclusion that intercellular infection is an active process that is dependent on bacterial Nod factor signaling.

scholarly journals The Medicago truncatula MtAnn1 Gene Encoding an Annexin Is Induced by Nod Factors and During the Symbiotic Interaction with Rhizobium meliloti

1998 ◽  
Vol 11 (6) ◽  
pp. 504-513 ◽  
Author(s):  
Fernanda de Carvalho Niebel ◽  
Nicole Lescure ◽  
Julie V. Cullimore ◽  
Pascal Gamas
Keyword(s):  
Medicago Truncatula ◽  
Rhizobium Meliloti ◽  
Marker Gene ◽  
Distal Region ◽  
Infection Process ◽  
Biologically Active ◽  
Nod Factors ◽  
Symbiotic Interaction ◽  
Symbiotic Associations ◽  
Infection Threads

Here we report the characterization of a new Nod factor-induced gene from Medicago truncatula identified by mRNA differential display. This gene, designated MtAnn1, encodes a protein homologous to the annexin family of calcium- and phospholipid-binding proteins. We further show that the MtAnn1 gene is also induced during symbiotic associations with Rhizobium meliloti, both at early stages in bacterial-inoculated roots and in nodule structures. By in situ hybridization, we demonstrate that MtAnn1 expression in nodules is mainly associated with the distal region of invasion zone II not containing infection threads, revealing MtAnn1 as a new marker gene of the pre-infection zone. Moreover, analyses of MtAnn1 expression in response to bacterial symbiotic mutants suggest that the expression of MtAnn1 during nodulation requires biologically active Nod factors and is independent of the infection process.

scholarly journals Evidence for the Involvement in Nodulation of the Two Small Putative Regulatory Peptide-Encoding Genes MtRALFL1 and MtDVL1

2008 ◽  
Vol 21 (8) ◽  
pp. 1118-1127 ◽  
Author(s):  
Jean-Philippe Combier ◽  
Helge Küster ◽  
Etienne-Pascal Journet ◽  
Natalija Hohnjec ◽  
Pascal Gamas ◽  
...  
Keyword(s):  
Nodule Development ◽  
Strong Increase ◽  
Nod Factors ◽  
Plant Host ◽  
Symbiotic Interaction ◽  
Nod Factor ◽  
Infection Threads ◽  
Genes Encoding ◽  
Supernodulating Mutant ◽  
Increased Sensitivity

Nod factors are key bacterial signaling molecules regulating the symbiotic interaction between bacteria known as rhizobia and leguminous plants. Studying plant host genes whose expression is affected by Nod factors has given insights into early symbiotic signaling and development. Here, we used a double supernodulating mutant line that shows increased sensitivity to Nod factors to study the Nod factor-regulated transcriptome. Using microarrays containing more than 16,000 70-mer oligonucleotide probes, we identified 643 Nod-factor-regulated genes, including 225 new Nod-factor-upregulated genes encoding many potential regulators. Among the genes found to be Nod factor upregulated, we identified and characterized MtRALFL1 and MtDVL1, which code for two small putative peptide regulators of 135 and 53 amino acids, respectively. Expression analysis confirmed that these genes are upregulated during initial phases of nodulation. Overexpression of MtRALFL1 and MtDVL1 in Medicago truncatula roots resulted in a marked reduction in the number of nodules formed and in a strong increase in the number of aborted infection threads. In addition, abnormal nodule development was observed when MtRALFL1 was overexpressed. This work provides evidence for the involvement of new putative small-peptide regulators during nodulation.

Identification of chromosome regions involved in the genetic regulation of tillering in barley ( Hordeum vulgare L.)

2006 ◽  
Vol 54 (1) ◽  
pp. 15-23 ◽  
Author(s):  
I. Karsai ◽  
K. Mészáros ◽  
L. Láng ◽  
Z. Bedő
Keyword(s):  
Mapping Population ◽  
Genetic Regulation ◽  
Heading Date ◽  
Complex Trait ◽  
Hordeum Vulgare L ◽  
Major Genes ◽  
Complex Regulation ◽  
Generative Phase ◽  
Spring Sowing ◽  
Chromosome Regions

Tillering ability is a complex trait, the development of which is influenced by both environmental factors and complex genetic regulation. In the present experiments this complex regulation was dissected into its various components in an effort to separate the effect on tillering of major genes influencing ontogeny from that of other genomic factors. The tillering rate of a facultative × winter barley mapping population was examined in the field after autumn and spring sowing. The vernalisation sensitivity gene Vrn-H2 exerted a considerable influence on tillering in spring-sown barley. In addition to the major genes, QTL analysis revealed two chromosome regions (1HS and 3HL) with a significant influence on the extent of tillering. Neither of these regions were involved in the regulation of heading date, and their effect on tillering was the most intense at the beginning of ontogeny, gradually declining as the influence of the Vrn-H2 gene increased. The function of the Vrn-H2 locus in the regulation of tillering is manifested partly through a direct effect on the transition from the vegetative to the generative phase and partly indirectly via epistatic regulation of other chromosome regions influencing tillering.

scholarly journals OnfD, an AraC-Type Transcriptional Regulator Encoded by Rhizobium tropici CIAT 899 and Involved in Nod Factor Synthesis and Symbiosis

2020 ◽  
Vol 86 (19) ◽  
Author(s):  
Pablo del Cerro ◽  
Paula Ayala-García ◽  
Pablo Buzón ◽  
Roger Castells-Graells ◽  
Francisco Javier López-Baena ◽  
...  
Keyword(s):  
Salt Stress ◽  
Osmotic Stress ◽  
Transcriptional Activation ◽  
Structural Model ◽  
Stress Conditions ◽  
Broad Host Range ◽  
Rhizobial Strain ◽  
Rhizobium Tropici ◽  
Symbiotic Interaction ◽  
Content Type

ABSTRACT Rhizobium tropici CIAT 899 is a broad-host-range rhizobial strain that establishes symbiotic interactions with legumes and tolerates different environmental stresses such as heat, acidity, or salinity. This rhizobial strain produces a wide variety of symbiotically active nodulation factors (NF) induced not only by the presence of plant-released flavonoids but also under osmotic stress conditions through the LysR-type transcriptional regulators NodD1 (flavonoids) and NodD2 (osmotic stress). However, the activation of NodD2 under high-osmotic-stress conditions remains elusive. Here, we have studied the role of a new AraC-type regulator (named as OnfD) in the symbiotic interaction of R. tropici CIAT 899 with Phaseolus vulgaris and Lotus plants. We determined that OnfD is required under salt stress conditions for the transcriptional activation of the nodulation genes and therefore the synthesis and export of NF, which are required for a successful symbiosis with P. vulgaris. Moreover, using bacterial two-hybrid analysis, we demonstrated that the OnfD and NodD2 proteins form homodimers and OnfD/NodD2 form heterodimers, which could be involved in the production of NF in the presence of osmotic stress conditions since both regulators are required for NF synthesis in the presence of salt. A structural model of OnfD is presented and discussed. IMPORTANCE The synthesis and export of rhizobial NF are mediated by a conserved group of LysR-type regulators, the NodD proteins. Here, we have demonstrated that a non-LysR-type regulator, an AraC-type protein, is required for the transcriptional activation of symbiotic genes and for the synthesis of symbiotically active NF under salt stress conditions.

scholarly journals Life at Home and on the Roam: Genomic Adaptions Reflect the Dual Lifestyle of an Intracellular, Facultative Symbiont

mSystems ◽  
2019 ◽  
Vol 4 (4) ◽  
Author(s):  
Ilia Burgsdorf ◽  
Kim M. Handley ◽  
Rinat Bar-Shalom ◽  
Patrick M. Erwin ◽  
Laura Steindler
Keyword(s):  
Defense Mechanisms ◽  
Genetic Regulation ◽  
Free Living ◽  
Symbiotic Interaction ◽  
Genomic Features ◽  
Content Type ◽  
Intracellular Symbiont ◽  
Stem Lineage ◽  
Associated Proteins ◽  
Sponge Symbionts

ABSTRACT “Candidatus Synechococcus feldmannii” is a facultative intracellular symbiont of the Atlanto-Mediterranean sponge Petrosia ficiformis. Genomic information of sponge-associated cyanobacteria derives thus far from the obligate and extracellular symbiont “Candidatus Synechococcus spongiarum.” Here we utilized a differential methylation-based approach for bacterial DNA enrichment combined with metagenomics to obtain the first draft genomes of “Ca. Synechococcus feldmannii.” By comparative genomics, we revealed that some genomic features (e.g., iron transport mediated by siderophores, eukaryotic-like proteins, and defense mechanisms, like CRISPR-Cas [clustered regularly interspaced short palindromic repeats-associated proteins]) are unique to both symbiont types and absent or rare in the genomes of taxonomically related free-living cyanobacteria. These genomic features likely enable life under the conditions found inside the sponge host. Interestingly, there are many genomic features that are shared by “Ca. Synechococcus feldmannii” and free-living cyanobacteria, while they are absent in the obligate symbiont “Ca. Synechococcus spongiarum.” These include genes related to cell surface structures, genetic regulation, and responses to environmental stress, as well as the composition of photosynthetic genes and DNA metabolism. We speculate that the presence of these genes confers on “Ca. Synechococcus feldmannii” its facultative nature (i.e., the ability to respond to a less stable environment when free-living). Our comparative analysis revealed that distinct genomic features depend on the nature of the symbiotic interaction: facultative and intracellular versus obligate and extracellular. IMPORTANCE Given the evolutionary position of sponges as one of the earliest phyla to depart from the metazoan stem lineage, studies on their distinct and exceptionally diverse microbial communities should yield a better understanding of the origin of animal-bacterium interactions. While genomes of several extracellular sponge symbionts have been published, the intracellular symbionts have, so far, been elusive. Here we compare the genomes of two unicellular cyanobacterial sponge symbionts that share an ancestor but followed different evolutionary paths—one became intracellular and the other extracellular. Counterintuitively, the intracellular cyanobacteria are facultative, while the extracellular ones are obligate. By sequencing the genomes of the intracellular cyanobacteria and comparing them to the genomes of the extracellular symbionts and related free-living cyanobacteria, we show how three different cyanobacterial lifestyles are reflected by adaptive genomic features.

scholarly journals Differential Expression of Paraburkholderia phymatum Type VI Secretion Systems (T6SS) Suggests a Role of T6SS-b in Early Symbiotic Interaction

2021 ◽  
Vol 12 ◽  
Author(s):  
Sebastian Hug ◽  
Yilei Liu ◽  
Benjamin Heiniger ◽  
Aurélien Bailly ◽  
Christian H. Ahrens ◽  
...  
Keyword(s):  
Root Nodules ◽  
Rhizobial Strain ◽  
Secretion Systems ◽  
Phenotypic Analysis ◽  
Free Living ◽  
Symbiotic Interaction ◽  
Type Vi Secretion ◽  
Mutant Strains

Paraburkholderia phymatum STM815, a rhizobial strain of the Burkholderiaceae family, is able to nodulate a broad range of legumes including the agriculturally important Phaseolus vulgaris (common bean). P. phymatum harbors two type VI Secretion Systems (T6SS-b and T6SS-3) in its genome that contribute to its high interbacterial competitiveness in vitro and in infecting the roots of several legumes. In this study, we show that P. phymatum T6SS-b is found in the genomes of several soil-dwelling plant symbionts and that its expression is induced by the presence of citrate and is higher at 20/28°C compared to 37°C. Conversely, T6SS-3 shows homologies to T6SS clusters found in several pathogenic Burkholderia strains, is more prominently expressed with succinate during stationary phase and at 37°C. In addition, T6SS-b expression was activated in the presence of germinated seeds as well as in P. vulgaris and Mimosa pudica root nodules. Phenotypic analysis of selected deletion mutant strains suggested a role of T6SS-b in motility but not at later stages of the interaction with legumes. In contrast, the T6SS-3 mutant was not affected in any of the free-living and symbiotic phenotypes examined. Thus, P. phymatum T6SS-b is potentially important for the early infection step in the symbiosis with legumes.

scholarly journals The Rhizobium etli trpB Gene Is Essential for an Effective Symbiotic Interaction with Phaseolus vulgaris

1999 ◽  
Vol 12 (10) ◽  
pp. 926-933 ◽  
Author(s):  
Rosarita Taté ◽  
Anna Riccio ◽  
Emilia Caputo ◽  
Michele Cermola ◽  
Renee Favre ◽  
...  
Keyword(s):  
Phaseolus Vulgaris ◽  
Homologous Gene ◽  
Tryptophan Synthase ◽  
Sole Nitrogen Source ◽  
Tryptophan Biosynthesis ◽  
Rhizobium Etli ◽  
Nod Factors ◽  
Free Living ◽  
Symbiotic Interaction ◽  
Free Living Conditions

A mutant strain (CTNUX4) of Rhizobium etli carrying Tn5 unable to grow with ammonium as the sole nitrogen source was isolated and characterized. Sequence analysis showed that Tn5 is inserted into a trpB (tryptophan synthase)-homologous gene. When tested on the roots of Phaseolus vulgaris, strain CTNUX4 was able to induce only small, slightly pink, ineffective (Fix¯) nodules. However, under free-living conditions, strain CTNUX4 was unable to produce flavonoid-inducible lipo-chitin oligosaccharides (Nod factors) unless tryptophan was added to the growth medium. These data and histological observations indicate that the lack of tryptophan biosynthesis affects the symbiotic behavior of R. etli.

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