A new type III effector from Bradyrhizobium sp. DOA9 encoding a putative SUMO-protease blocks nodulation in Arachis hypogaea L.

Effector proteins secreted via the type III secretion system (T3SS) of nitrogen-fixing rhizobia are key determinants of symbiotic compatibility in legumes. Previous report revealed that the T3SS of Bradyrhizobium sp. DOA9 plays negative effects on Arachis hypogaea symbiosis.

Genetic and transcriptomic analysis of the Bradyrhizobium T3SS-triggered nodulation in the legume Aeschynomene evenia.

Some Bradyrhizobium strains nodulate certain Aeschynomene species independently of Nod factors, but thanks to their type III secretion system (T3SS). While different T3 effectors triggering nodulation (ErnA and Sup3) have been identified, the plant signalling pathways they activate remain unknown. Here, we explored the intraspecies variability in T3SS-triggered nodulation within Aeschynomene evenia and investigated transcriptomic responses that occur during this symbiosis.

Pathogenic nematodes exploit Achilles' heel of plant symbioses.

Cyst nematode parasites disrupt beneficial associations of crops with rhizobia and mycorrhiza. Chen et al. discovered the mechanism and demonstrated that the soybean cyst nematode Heterodera glycines secretes a chitinase that destroys key symbiotic signals from the microbial symbionts.

Exploring the cellular surface polysaccharide and root nodule symbiosis characteristics of the mutants of sp. DOA9 using synchrotron-based Fourier transform infrared microspectroscopy in conjunction with X-ray absorption spectroscopy.

The functional significance of genes that encode two sigma factors in the sp. strain DOA9 has been reported to affect colony formation, root nodulation characteristics, and symbiotic interactions with mutant strains are defective in cellular surface polysaccharide (CSP) production compared with the wild-type (WT) strain, and they accordingly exhibit smaller colonies and diminished symbiotic effectiveness. To gain deeper insights into the changes in CSP composition and the nodules of mutants, we employed synchrotron-based Fourier transform infrared (SR-FTIR) microspectroscopy and X-ray absorption spectroscopy.

Widespread Bradyrhizobium distribution of diverse Type III effectors that trigger legume nodulation in the absence of Nod factor.

The establishment of the rhizobium-legume symbiosis is generally based on plant perception of Nod factors (NFs) synthesized by the bacteria. However, some Bradyrhizobium strains can nodulate certain legume species, such as Aeschynomene spp. or Glycine max, independently of NFs, and via two different processes that are distinguished by the necessity or not of a type III secretion system (T3SS).

Expanding Knowledge of Methylotrophic Capacity: Structure and Properties of the Rough-Type Lipopolysaccharide from and Its Role on Membrane Resistance to Methanol.

The ability of to grow on methanol as the sole carbon and energy source has been the object of intense research activity. Unquestionably, the bacterial cell envelope serves as a defensive barrier against such an environmental stressor, with a decisive role played by the membrane lipidome, which is crucial for stress resistance. However, the chemistry and the function of the main constituent of the outer membrane, the lipopolysaccharide (LPS), is still undefined.

Role of two RpoN in sp. strain DOA9 in symbiosis and free-living growth.

RpoN is an alternative sigma factor (sigma 54) that recruits the core RNA polymerase to promoters of genes. In bacteria, RpoN has diverse physiological functions. In rhizobia, RpoN plays a key role in the transcription of nitrogen fixation () genes.

A mutant-based analysis of the establishment of Nod-independent symbiosis in the legume Aeschynomene evenia.

Intensive research on nitrogen-fixing symbiosis in two model legumes has uncovered the molecular mechanisms, whereby rhizobial Nod factors activate a plant symbiotic signaling pathway that controls infection and nodule organogenesis. In contrast, the so-called Nod-independent symbiosis found between Aeschynomene evenia and photosynthetic bradyrhizobia, which does not involve Nod factor recognition nor infection thread formation, is less well known. To gain knowledge on how Nod-independent symbiosis is established, we conducted a phenotypic and molecular characterization of A.

The Versatile Roles of Type III Secretion Systems in Rhizobium-Legume Symbioses.

To suppress plant immunity and promote the intracellular infection required for fixing nitrogen for the benefit of their legume hosts, many rhizobia use type III secretion systems (T3SSs) that deliver effector proteins (T3Es) inside host cells. As reported for interactions between pathogens and host plants, the immune system of legume hosts and the cocktail of T3Es secreted by rhizobia determine the symbiotic outcome. If they remain undetected, T3Es may reduce plant immunity and thus promote infection of legumes by rhizobia.

The Type III Effectome of the Symbiotic Strain ORS3257.

Many strains are able to establish a Nod factor-independent symbiosis with the leguminous plant by the use of a type III secretion system (T3SS). Recently, an important advance in the understanding of the molecular factors supporting this symbiosis has been achieved by the in silico identification and functional characterization of 27 putative T3SS effectors (T3Es) of ORS3257. In the present study, we experimentally extend this catalog of T3Es by using a multi-omics approach.

A glutamate synthase mutant of Bradyrhizobium sp. strain ORS285 is unable to induce nodules on Nod factor-independent Aeschynomene species.

The Bradyrhizobium sp. strain ORS285 is able to establish a nitrogen-fixing symbiosis with both Nod factor (NF) dependent and NF-independent Aeschynomene species. Here, we have studied the growth characteristics and symbiotic interaction of a glutamate synthase (GOGAT; gltD::Tn5) mutant of Bradyrhizobium ORS285.

Identification of type III effectors modulating the symbiotic properties of Bradyrhizobium vignae strain ORS3257 with various Vigna species.

The Bradyrhizobium vignae strain ORS3257 is an elite strain recommended for cowpea inoculation in Senegal. This strain was recently shown to establish symbioses on some Aeschynomene species using a cocktail of Type III effectors (T3Es) secreted by the T3SS machinery. In this study, using a collection of mutants in different T3Es genes, we sought to identify the effectors that modulate the symbiotic properties of ORS3257 in three Vigna species (V.

Genetics of nodulation in Aeschynomene evenia uncovers mechanisms of the rhizobium-legume symbiosis.

Among legumes (Fabaceae) capable of nitrogen-fixing nodulation, several Aeschynomene spp. use a unique symbiotic process that is independent of Nod factors and infection threads. They are also distinctive in developing root and stem nodules with photosynthetic bradyrhizobia.

Rhizobia use a pathogenic-like effector to hijack leguminous nodulation signalling.

Legume plants form a root-nodule symbiosis with rhizobia. This symbiosis establishment generally relies on rhizobium-produced Nod factors (NFs) and their perception by leguminous receptors (NFRs) that trigger nodulation. However, certain rhizobia hijack leguminous nodulation signalling via their type III secretion system, which functions in pathogenic bacteria to deliver effector proteins into host cells.

RibBX of ORS285 Plays an Important Role in Intracellular Persistence in Various Host Plants.

Bradyrhizobium ORS285 forms a nitrogen-fixating symbiosis with both Nod factor (NF)-dependent and NF-independent spp. The ORS285 gene encodes for a putative bifunctional enzyme with 3,4-dihydroxybutanone phosphate (3,4-DHBP) synthase and guanosine triphosphate (GTP) cyclohydrolase II activities, catalyzing the initial steps in the riboflavin biosynthesis pathway. In this study, we show that inactivating the gene does not cause riboflavin auxotrophy under free-living conditions and that, as shown for RibBAs from other bacteria, the GTP cyclohydrolase II domain has no enzymatic activity.

The Peculiar Structure of Acetobacter pasteurianus CIP103108 LPS Core Oligosaccharide.

Acetobacter pasteurianus, a member of the Alphaproteobacteria, is an acetic acid-producing bacterium present on sugar-rich substrates such as such as fruits, flowers and vegetables and traditionally used in the production of fermented food. The preferred living habitat associated with acid conditions makes the structure of the bacterial cell wall interesting to study, due to expected uncommon features. We have used a combination of chemical, analytical and NMR spectroscopy approaches to define the complete structure of the core oligosaccharide from A.

Phylogenetic distribution and evolutionary dynamics of and T3SS genes in the genus .

are abundant soil bacteria and the major symbiont of legumes. The recent availability of genome sequences provides a large source of information for analysis of symbiotic traits. In this study, we investigated the evolutionary dynamics of the nodulation genes () and their relationship with the genes encoding type III secretion systems (T3SS) and their effectors among bradyrhizobia.

The rhizobial type III effector ErnA confers the ability to form nodules in legumes.

Several species nodulate the leguminous plant in a type III secretion system-dependent manner, independently of Nod factors. To date, the underlying molecular determinants involved in this symbiotic process remain unknown. To identify the rhizobial effectors involved in nodulation, we mutated 23 out of the 27 effector genes predicted in strain ORS3257.

The Modification of the Flavonoid Naringenin by sp. Strain ORS285 Changes the Genes Inducer Function to a Growth Stimulator.

As inducers of nodulation () genes, flavonoids play an important role in the symbiotic interaction between rhizobia and legumes. However, in addition to the control of expression of genes, many other effects of flavonoids on rhizobial cells have been described. Here, we show that the flavonoid naringenin stimulates the growth of the photosynthetic sp.

Symbiotic properties of a chimeric Nod-independent photosynthetic Bradyrhizobium strain obtained by conjugative transfer of a symbiotic plasmid.

The lateral transfer of symbiotic genes converting a predisposed soil bacteria into a legume symbiont has occurred repeatedly and independently during the evolution of rhizobia. We experimented the transfer of a symbiotic plasmid between Bradyrhizobium strains. The originality of the DOA9 donor is that it harbours a symbiotic mega-plasmid (pDOA9) containing nod, nif and T3SS genes while the ORS278 recipient has the unique property of inducing nodules on some Aeschynomene species in the absence of Nod factors (NFs).

Complete Genome Sequence of sp. Strain ORS3257, an Efficient Nitrogen-Fixing Bacterium Isolated from Cowpea in Senegal.

Here, we report the complete genome sequence of Bradyrhizobium sp. strain ORS3257, which forms efficient symbioses with cowpea, peanut, or groundnut. These genomic data will be useful to identify genes associated with symbiotic performance and host compatibility on several legumes, including Aeschynomene species, with which a Nod-independent type III secretion system (T3SS)-dependent symbiosis can be established.

Mutualistic co-evolution of T3SSs during the establishment of symbiotic relationships between Vigna radiata and Bradyrhizobia.

This study supports the idea that the evolution of type III secretion system (T3SS) is one of the factors that controls Vigna radiata-bradyrhizobia symbiosis. Based on phylogenetic tree data and gene arrangements, it seems that the T3SSs of the Thai bradyrhizobial strains SUTN9-2, DOA1, and DOA9 and the Senegalese strain ORS3257 may share the same origin. Therefore, strains SUTN9-2, DOA1, DOA9, and ORS3257 may have evolved their T3SSs independently from other bradyrhizobia, depending on biological and/or geological events.