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 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 Asymmetric Redundancy of Soybean Nodule Inception (NIN) Genes in Root Nodule Symbiosis

2021 ◽  
Author(s):  
Mengdi Fu ◽  
Jiafeng Sun ◽  
Xiaolin Li ◽  
Yuefeng Guan ◽  
Fang Xie
Keyword(s):  
Root Nodule ◽  
Minor Role ◽  
Nodule Formation ◽  
Wild Type ◽  
Promoter Regions ◽  
Triple Mutant ◽  
Symbiotic Interaction ◽  
Root Nodule Symbiosis ◽  
A Minor ◽  
Nodule Symbiosis

NIN is one of the most important root nodule symbiotic genes as it is required for both infection and nodule organogenesis in legume. Unlike most legumes with a sole NIN gene, there are four putative NIN genes in soybean (Glycine max). Whether and how these orthologs NIN genes contribute to soybean-rhizobia symbiotic interaction remain unknown. In this study, we found that all four GmNIN genes are induced by rhizobia, and that conserved CE and CYC binding motifs in their promoter regions are required for their expression in the nodule formation process. By generation of multiplex Gmnin mutants, we found that Gmnin1a nin2a nin2b triple mutant and Gmnin1a nin1b nin2a nin2b quadruple mutant displayed similar defects in rhizobia infection and root nodule formation, Gmnin2a nin2b produced less nodules but displayed hyper infection phenotype than wild type, while a Gmnin1a nin1b double mutant nodulated as wild type. Overexpression of GmNIN1a, GmNIN1b, GmNIN2a, and GmNIN2b reduced nodule numbers after rhizobia inoculation, with GmNIN1b overexpression having the weakest effect. In addition, overexpression of GmNIN1a, GmNIN2a, or GmNIN2b, but not GmNIN1b, produced malformed pseudo-nodule like structures without rhizobia inoculation. In conclusion, GmNIN1a, GmNIN2a and GmNIN2b play functionally redundant yet complicated roles for soybean nodulation. GmNIN1b, although is expressed at comparable level with other homologs, plays a minor role in root nodule symbiosis. Our work provides insight into the understanding of asymmetrically redundant function of GmNIN genes in soybean.

scholarly journals Phosphatidylethanolamine Is Not Essential for Growth of Sinorhizobium meliloti on Complex Culture Media

2004 ◽  
Vol 186 (6) ◽  
pp. 1667-1677 ◽  
Author(s):  
Christian Sohlenkamp ◽  
Karel E. E. de Rudder ◽  
Otto Geiger
Keyword(s):  
Sinorhizobium Meliloti ◽  
Minimal Medium ◽  
Membrane Lipids ◽  
Culture Media ◽  
Membrane Lipid ◽  
Deficient Mutant ◽  
Wild Type ◽  
Phosphatidylserine Synthase ◽  
Growth Phenotype ◽  
Complex Culture

ABSTRACT In addition to phosphatidylglycerol (PG), cardiolipin (CL), and phosphatidylethanolamine (PE), Sinorhizobium meliloti also possesses phosphatidylcholine (PC) as a major membrane lipid. The biosynthesis of PC in S. meliloti can occur via two different routes, either via the phospholipid N-methylation pathway, in which PE is methylated three times in order to obtain PC, or via the phosphatidylcholine synthase (Pcs) pathway, in which choline is condensed with CDP-diacylglycerol to obtain PC directly. Therefore, for S. meliloti, PC biosynthesis can occur via PE as an intermediate or via a pathway that is independent of PE, offering the opportunity to uncouple PC biosynthesis from PE biosynthesis. In this study, we investigated the first step of PE biosynthesis in S. meliloti catalyzed by phosphatidylserine synthase (PssA). A sinorhizobial mutant lacking PE was complemented with an S. meliloti gene bank, and the complementing DNA was sequenced. The gene coding for the sinorhizobial phosphatidylserine synthase was identified, and it belongs to the type II phosphatidylserine synthases. Inactivation of the sinorhizobial pssA gene leads to the inability to form PE, and such a mutant shows a greater requirement for bivalent cations than the wild type. A sinorhizobial PssA-deficient mutant possesses only PG, CL, and PC as major membrane lipids after growth on complex medium, but it grows nearly as well as the wild type under such conditions. On minimal medium, however, the PE-deficient mutant shows a drastic growth phenotype that can only partly be rescued by choline supplementation. Therefore, although choline permits Pcs-dependent PC formation in the mutant, it does not restore wild-type-like growth in minimal medium, suggesting that it is not only the lack of PC that leads to this drastic growth phenotype.

scholarly journals Asymmetric Redundancy of Soybean Nodule Inception (NIN) Genes in Root Nodule Symbiosis

2021 ◽  
Author(s):  
Mengdi Fu ◽  
Jiafeng Sun ◽  
Xiaolin Li ◽  
Yuefeng Guan ◽  
Fang Xie
Keyword(s):  
Root Nodule ◽  
Minor Role ◽  
Nodule Formation ◽  
Wild Type ◽  
Promoter Regions ◽  
Triple Mutant ◽  
Symbiotic Interaction ◽  
Root Nodule Symbiosis ◽  
A Minor ◽  
Nodule Symbiosis

Abstract Nodule Inception (NIN) is one of the most important root nodule symbiotic genes as it is required for both infection and nodule organogenesis in legumes. Unlike most legumes with a sole NIN gene, there are four putative orthologous NIN genes in soybean (Glycine max). Whether and how these NIN genes contribute to soybean-rhizobia symbiotic interaction remain unknown. In this study, we found that all four GmNIN genes are induced by rhizobia and that conserved CE and CYC binding motifs in their promoter regions are required for their expression in the nodule formation process. By generation of multiplex Gmnin mutants, we found that the Gmnin1a nin2a nin2b triple mutant and Gmnin1a nin1b nin2a nin2b quadruple mutant displayed similar defects in rhizobia infection and root nodule formation, Gmnin2a nin2b produced fewer nodules but displayed a hyper infection phenotype compared to wild type, while the Gmnin1a nin1b double mutant nodulated similar to wild type. Overexpression of GmNIN1a, GmNIN1b, GmNIN2a, and GmNIN2b reduced nodule numbers after rhizobia inoculation, with GmNIN1b overexpression having the weakest effect. In addition, overexpression of GmNIN1a, GmNIN2a, or GmNIN2b, but not GmNIN1b, produced malformed pseudo-nodule-like structures without rhizobia inoculation. In conclusion, GmNIN1a, GmNIN2a, and GmNIN2b play functionally redundant yet complicated roles in soybean nodulation. GmNIN1b, although expressed at a comparable level with the other homologs, plays a minor role in root nodule symbiosis. Our work provides insight into the understanding of the asymmetrically redundant function of GmNIN genes in soybean.

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

scholarly journals Functional and comparative genomics reveals conserved noncoding sequences in the nitrogen-fixing clade

2021 ◽  
Author(s):  
Wendell J Pereira ◽  
Sara A Knaack ◽  
Daniel Conde ◽  
Sanhita Chakraborty ◽  
Ryan A Folk ◽  
...  
Keyword(s):  
Root Nodule ◽  
Chromatin Accessibility ◽  
Regulatory Sequences ◽  
Regulation Of Transcription ◽  
Nitrogen Fixing ◽  
Noncoding Sequences ◽  
Functional Conservation ◽  
Root Nodule Symbiosis ◽  
Conserved Noncoding Sequences ◽  
Nodule Symbiosis

Nitrogen is one of the most inaccessible plant nutrients, but certain species have overcome this limitation by establishing symbiotic interactions with nitrogen-fixing bacteria in the root nodule. This root nodule symbiosis (RNS) is restricted to species within a single clade of angiosperms, suggesting a critical evolutionary event at the base of this clade, which has not yet been determined. While genes implicated in the RNS are present in most plant species (nodulating or not), gene sequence conservation alone does not imply functional conservation - developmental or phenotypic differences can arise from variation in the regulation of transcription. To identify putative regulatory sequences implicated in the evolution of RNS, we aligned the genomes of 25 species capable of nodulation. We detected 3,091 conserved noncoding sequences (CNS) in the nitrogen-fixing clade that are absent from outgroup species. Functional analysis revealed that chromatin accessibility of 452 CNS significantly correlates with the differential regulation of genes responding to lipo-chitooligosaccharides in Medicago truncatula. These included 38 CNS in proximity to 19 known genes involved in RNS. Five such regions are upstream of MtCRE1, Cytokinin Response Element 1, required to activate a suite of downstream transcription factors necessary for nodulation in M. truncatula. Genetic complementation of a Mtcre1 mutant showed a significant association between nodulation and the presence of these CNS, when they are driving the expression of a functional copy of MtCRE1. Conserved noncoding sequences, therefore, may be required for the regulation of genes controlling the root nodule symbiosis in M. truncatula.

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