scholarly journals Disruption of a Gene Essential for Sulfoquinovosyldiacylglycerol Biosynthesis in Sinorhizobium meliloti Has No Detectable Effect on Root Nodule Symbiosis

2000 ◽  
Vol 13 (6) ◽  
pp. 666-672 ◽  
Author(s):  
Barbara Weissenmayer ◽  
Otto Geiger ◽  
Christoph Benning
Keyword(s):  
Sinorhizobium Meliloti ◽  
Root Nodule ◽  
Membrane Lipids ◽  
Growth Conditions ◽  
Laboratory Culture ◽  
Culture Conditions ◽  
Detectable Effect ◽  
Purple Bacterium ◽  
Root Nodule Symbiosis ◽  
Nodule Symbiosis

The sulfolipid sulfoquinovosyldiacylglycerol is commonly found in the thylakoid membranes of photosynthetic bacteria and plants. While there is a good correlation between the occurrence of sulfolipid and photosynthesis, a number of exceptions are known. Most recently, sulfoquinovosyldiacylglycerol was discovered in the non-photosynthetic, root nodule-forming bacterium Sinorhizobium meliloti. This discovery raised the questions of the phylogenetic origin of genes essential for the biosynthesis of this lipid in S. meliloti and of a function of sulfolipid in root nodule symbiosis. To begin to answer these questions, we isolated and inactivated the sqdB gene of S. meliloti. This gene and two other genes located directly 3′ of sqdB are highly similar to the sqdB, sqdC, and sqdD genes known to be essential for sulfolipid biosynthesis in the photosynthetic, purple bacterium Rhodobacter sphaeroides. This observation confirms the close phylogenetic kinship between these two species. Furthermore, the reduced similarity of sqdB to the plant ortholog SQD1 of Arabidopsis thaliana does not support a previous sqd gene transfer from the plant as a consequence of close symbiosis. A sul-folipid-deficient mutant of S. meliloti disrupted in sqdB is capable of inducing functional nodules and does not show an obvious disadvantage under different laboratory culture conditions. Thus far, no specific function can be assigned to bacterial sulfolipid, in either nodule-associated or free-living cells. S. meliloti contains a rich set of polar membrane lipids some of which, including sulfolipid, may become critical only under growth conditions that still need to be discovered.

scholarly journals Sinorhizobium meliloti Mutants Deficient in Phosphatidylserine Decarboxylase Accumulate Phosphatidylserine and Are Strongly Affected during Symbiosis with Alfalfa

2008 ◽  
Vol 190 (20) ◽  
pp. 6846-6856 ◽  
Author(s):  
Miguel Angel Vences-Guzmán ◽  
Otto Geiger ◽  
Christian Sohlenkamp
Keyword(s):  
Sinorhizobium Meliloti ◽  
Minimal Medium ◽  
Root Nodule ◽  
Membrane Lipids ◽  
Nodule Formation ◽  
Deficient Mutant ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Root Nodule Symbiosis ◽  
Nodule Symbiosis

ABSTRACT Sinorhizobium meliloti contains phosphatidylglycerol, cardiolipin, phosphatidylcholine, and phosphatidylethanolamine (PE) as major membrane lipids. PE is formed in two steps. In the first step, phosphatidylserine synthase (Pss) condenses serine with CDP-diglyceride to form phosphatidylserine (PS), and in the second step, PS is decarboxylated by phosphatidylserine decarboxylase (Psd) to form PE. In this study we identified the sinorhizobial psd gene coding for Psd. A sinorhizobial mutant deficient in psd is unable to form PE but accumulates the anionic phospholipid PS. Properties of PE-deficient mutants lacking either Pss or Psd were compared with those of the S. meliloti wild type. Whereas both PE-deficient mutants grew in a wild-type-like manner on many complex media, they were unable to grow on minimal medium containing high phosphate concentrations. Surprisingly, the psd-deficient mutant could grow on minimal medium containing low concentrations of inorganic phosphate, while the pss-deficient mutant could not. Addition of choline to the minimal medium rescued growth of the pss-deficient mutant, CS111, to some extent but inhibited growth of the psd-deficient mutant, MAV01. When the two distinct PE-deficient mutants were analyzed for their ability to form a nitrogen-fixing root nodule symbiosis with their alfalfa host plant, they behaved strikingly differently. The Pss-deficient mutant, CS111, initiated nodule formation at about the same time point as the wild type but did form about 30% fewer nodules than the wild type. In contrast, the PS-accumulating mutant, MAV01, initiated nodule formation much later than the wild type and formed 90% fewer nodules than the wild type. The few nodules formed by MAV01 seemed to be almost devoid of bacteria and were unable to fix nitrogen. Leaves of alfalfa plants inoculated with the mutant MAV01 were yellowish, indicating that the plants were starved for nitrogen. Therefore, changes in lipid composition, including the accumulation of bacterial PS, prevent the establishment of a nitrogen-fixing root nodule symbiosis.

scholarly journals A Bifunctional UDP-Sugar 4-Epimerase Supports Biosynthesis of Multiple Cell Surface Polysaccharides in Sinorhizobium meliloti

2019 ◽  
Vol 201 (10) ◽  
Author(s):  
Simon Schäper ◽  
Heiko Wendt ◽  
Jan Bamberger ◽  
Volker Sieber ◽  
Jochen Schmid ◽  
...  
Keyword(s):  
Biofilm Formation ◽  
Sinorhizobium Meliloti ◽  
Root Nodule ◽  
Extracellular Polysaccharides ◽  
Cell Protection ◽  
Content Type ◽  
Polysaccharide Biosynthesis ◽  
Root Nodule Symbiosis ◽  
Nodule Symbiosis

ABSTRACT Sinorhizobium meliloti produces multiple extracellular glycans, including among others, lipopolysaccharides (LPS), and the exopolysaccharides (EPS) succinoglycan (SG) and galactoglucan (GG). These polysaccharides serve cell protective roles. Furthermore, SG and GG promote the interaction of S. meliloti with its host Medicago sativa in root nodule symbiosis. ExoB has been suggested to be the sole enzyme catalyzing synthesis of UDP-galactose in S. meliloti (A. M. Buendia, B. Enenkel, R. Köplin, K. Niehaus, et al. Mol Microbiol 5:1519–1530, 1991, https://doi.org/10.1111/j.1365-2958.1991.tb00799.x). Accordingly, exoB mutants were previously found to be affected in the synthesis of the galactose-containing glycans LPS, SG, and GG and consequently, in symbiosis. Here, we report that the S. meliloti Rm2011 uxs1-uxe-apsS-apsH1-apsE-apsH2 (SMb20458-63) gene cluster directs biosynthesis of an arabinose-containing polysaccharide (APS), which contributes to biofilm formation, and is solely or mainly composed of arabinose. Uxe has previously been identified as UDP-xylose 4-epimerase. Collectively, our data from mutational and overexpression analyses of the APS biosynthesis genes and in vitro enzymatic assays indicate that Uxe functions as UDP-xylose 4- and UDP-glucose 4-epimerase catalyzing UDP-xylose/UDP-arabinose and UDP-glucose/UDP-galactose interconversions, respectively. Overexpression of uxe suppressed the phenotypes of an exoB mutant, evidencing that Uxe can functionally replace ExoB. We suggest that under conditions stimulating expression of the APS biosynthesis operon, Uxe contributes to the synthesis of multiple glycans and thereby to cell protection, biofilm formation, and symbiosis. Furthermore, we show that the C2H2 zinc finger transcriptional regulator MucR counteracts the previously reported CuxR–c-di-GMP-mediated activation of the APS biosynthesis operon. This integrates the c-di-GMP-dependent control of APS production into the opposing regulation of EPS biosynthesis and swimming motility in S. meliloti. IMPORTANCE Bacterial extracellular polysaccharides serve important cell protective, structural, and signaling roles. They have particularly attracted attention as adhesives and matrix components promoting biofilm formation, which significantly contributes to resistance against antibiotics. In the root nodule symbiosis between rhizobia and leguminous plants, extracellular polysaccharides have a signaling function. UDP-sugar 4-epimerases are important enzymes in the synthesis of the activated sugar substrates, which are frequently shared between multiple polysaccharide biosynthesis pathways. Thus, these enzymes are potential targets to interfere with these pathways. Our finding of a bifunctional UDP-sugar 4-epimerase in Sinorhizobium meliloti generally advances the knowledge of substrate promiscuity of such enzymes and specifically of the biosynthesis of extracellular polysaccharides involved in biofilm formation and symbiosis in this alphaproteobacterium.

scholarly journals Aboveground plant-to-plant communication reduces root nodule symbiosis and soil nutrient concentrations

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yuta Takahashi ◽  
Kaori Shiojiri ◽  
Akira Yamawo
Keyword(s):  
Root Nodule ◽  
Total Phenolics ◽  
Root Nodules ◽  
Soil Nutrient ◽  
Chemical Defenses ◽  
Nutrient Concentrations ◽  
Soil C ◽  
Plant Communication ◽  
Root Nodule Symbiosis ◽  
Nodule Symbiosis

AbstractAboveground communication between plants is well known to change defense traits in leaves, but its effects on belowground plant traits and soil characteristics have not been elucidated. We hypothesized that aboveground plant-to-plant communication reduces root nodule symbiosis via induction of bactericidal chemical defense substances and changes the soil nutrient environment. Soybean plants were exposed to the volatile organic compounds (VOCs) from damaged shoots of Solidago canadensis var. scabra, and leaf defense traits (total phenolics, saponins), root saponins, and root nodule symbiosis traits (number and biomass of root nodules) were measured. Soil C/N ratios and mineral concentrations were also measured to estimate the effects of resource uptake by the plants. We found that total phenolics were not affected. However, plants that received VOCs had higher saponin concentrations in both leaves and roots, and fewer root nodules than untreated plants. Although the concentrations of soil minerals did not differ between treatments, soil C/N ratio was significantly higher in the soil of communicated plants. Thus, the aboveground plant-to-plant communication led to reductions in root nodule symbiosis and soil nutrient concentrations. Our results suggest that there are broader effects of induced chemical defenses in aboveground plant organs upon belowground microbial interactions and soil nutrients, and emphasize that plant response based on plant-to-plant communications are a bridge between above- and below-ground ecosystems.

scholarly journals SymGRASS: a database of sugarcane orthologous genes involved in arbuscular mycorrhiza and root nodule symbiosis

2013 ◽  
Vol 14 (S1) ◽  
Author(s):  
Luis Carlos Belarmino ◽  
Roberta Lane de Oliveira Silva ◽  
Nina da Mota Soares Cavalcanti ◽  
Nicolas Krezdorn ◽  
Ederson Akio Kido ◽  
...  
Keyword(s):  
Arbuscular Mycorrhiza ◽  
Root Nodule ◽  
Orthologous Genes ◽  
Root Nodule Symbiosis ◽  
Nodule Symbiosis

scholarly journals Molecular Basis of Root Nodule Symbiosis between Bradyrhizobium and ‘Crack-Entry’ Legume Groundnut (Arachis hypogaea L.)

Plants ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 276 ◽  
Author(s):  
Vinay Sharma ◽  
Samrat Bhattacharyya ◽  
Rakesh Kumar ◽  
Ashish Kumar ◽  
Fernando Ibañez ◽  
...  
Keyword(s):  
Sustainable Agriculture ◽  
Root Nodule ◽  
Crop Productivity ◽  
Bacterial Attachment ◽  
Nodule Development ◽  
Bacterial Invasion ◽  
Crop Species ◽  
Symbiotic Relationships ◽  
Root Nodule Symbiosis ◽  
Nodule Symbiosis

Nitrogen is one of the essential plant nutrients and a major factor limiting crop productivity. To meet the requirements of sustainable agriculture, there is a need to maximize biological nitrogen fixation in different crop species. Legumes are able to establish root nodule symbiosis (RNS) with nitrogen-fixing soil bacteria which are collectively called rhizobia. This mutualistic association is highly specific, and each rhizobia species/strain interacts with only a specific group of legumes, and vice versa. Nodulation involves multiple phases of interactions ranging from initial bacterial attachment and infection establishment to late nodule development, characterized by a complex molecular signalling between plants and rhizobia. Characteristically, legumes like groundnut display a bacterial invasion strategy popularly known as “crack-entry’’ mechanism, which is reported approximately in 25% of all legumes. This article accommodates critical discussions on the bacterial infection mode, dynamics of nodulation, components of symbiotic signalling pathway, and also the effects of abiotic stresses and phytohormone homeostasis related to the root nodule symbiosis of groundnut and Bradyrhizobium. These parameters can help to understand how groundnut RNS is programmed to recognize and establish symbiotic relationships with rhizobia, adjusting gene expression in response to various regulations. This review further attempts to emphasize the current understanding of advancements regarding RNS research in the groundnut and speculates on prospective improvement possibilities in addition to ways for expanding it to other crops towards achieving sustainable agriculture and overcoming environmental challenges.

scholarly journals A New Species of Devosia That Forms a Unique Nitrogen-Fixing Root-Nodule Symbiosis with the Aquatic Legume Neptunia natans (L.f.) Druce

2002 ◽  
Vol 68 (11) ◽  
pp. 5217-5222 ◽  
Author(s):  
Raul Rivas ◽  
Encarna Velázquez ◽  
Anne Willems ◽  
Nieves Vizcaíno ◽  
Nanjappa S. Subba-Rao ◽  
...  
Keyword(s):  
Root Nodule ◽  
Root Nodules ◽  
Infection Process ◽  
Nitrogen Fixing ◽  
Rhizobium Tropici ◽  
Rdna Sequences ◽  
Root Nodule Symbiosis ◽  
16S Rdna Sequences ◽  
The Common ◽  
Nodule Symbiosis

ABSTRACT Rhizobia are the common bacterial symbionts that form nitrogen-fixing root nodules in legumes. However, recently other bacteria have been shown to nodulate and fix nitrogen symbiotically with these plants. Neptunia natans is an aquatic legume indigenous to tropical and subtropical regions and in African soils is nodulated by Allorhizobium undicola. This legume develops an unusual root-nodule symbiosis on floating stems in aquatic environments through a unique infection process. Here, we analyzed the low-molecular-weight RNA and 16S ribosomal DNA (rDNA) sequence of the same fast-growing isolates from India that were previously used to define the developmental morphology of the unique infection process in this symbiosis with N. natans and found that they are phylogenetically located in the genus Devosia, not Allorhizobium or Rhizobium. The 16S rDNA sequences of these two Neptunia-nodulating Devosia strains differ from the only species currently described in that genus, Devosia riboflavina. From the same isolated colonies, we also located their nodD and nifH genes involved in nodulation and nitrogen fixation on a plasmid of approximately 170 kb. Sequence analysis showed that their nodD and nifH genes are most closely related to nodD and nifH of Rhizobium tropici, suggesting that this newly described Neptunia-nodulating Devosia species may have acquired these symbiotic genes by horizontal transfer.

Phylogenomics reveals multiple losses of nitrogen-fixing root nodule symbiosis

Science ◽  
2018 ◽  
pp. eaat1743 ◽  
Author(s):  
Maximilian Griesmann ◽  
Yue Chang ◽  
Xin Liu ◽  
Yue Song ◽  
Georg Haberer ◽  
...  
Keyword(s):  
Root Nodule ◽  
Nitrogen Fixing ◽  
Root Nodule Symbiosis ◽  
Nodule Symbiosis
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