Sinorhizobium meliloti nifA mutant induces different gene expression profile from wild type in Alfalfa nodules

Gong, Zi Ying; He, Zhi Shui; Zhu, Jia; Guan, Yu; Zou, Hua Song

doi:10.1038/sj.cr.7310096

“…In contrast, its expression was equal to controls in the less MtSucS1-reduced line as19. Notably, dctA expression in response to C 4 dicarboxylates and the activation of the N 2 fixation (nif ) and fixation ( fix) operons are thought to be controlled via regulatory transcriptional activator NifA (SMa0815; Gong et al, 2006). In transgenic line as12, nifA expression was similar to controls, whereas a minor gene induction was found in as19 root nodules (Supplemental Table S2).…”

Section: Mtsucs1 Reduction Affects the Expression Of Genes Connected mentioning

confidence: 85%

Antisense Repression of the Medicago truncatula Nodule-Enhanced Sucrose Synthase Leads to a Handicapped Nitrogen Fixation Mirrored by Specific Alterations in the Symbiotic Transcriptome and Metabolome

Baier

¹

,

Barsch

²

,

Küster

³

et al. 2007

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We analyzed the role of the sucrose (Suc) synthase MtSucS1 during nodulation of the model legume Medicago truncatula, integrating data for the developmental, transcriptional, and metabolic processes affected downstream of an impaired Suc cleavage in root nodules. To reduce carbohydrate supply to nodule tissues, transgenic plants expressing a p35S-driven MtSucS1-antisense fusion were constructed. These plants displayed an up to 90% reduction of MtSucS1 proteins in roots and nodules. Phenotypic studies of two independent MtSucS1-reduced lines demonstrated that only under conditions depending on nodulation, these plants appeared to be impaired in above-ground growth. Specifically plant height, shoot weight, leaf development, flowering, as well as seed maturation were reduced, and the efficiency of photosynthesis was affected. Concomitantly, a significantly enhanced root to shoot ratio with a marked increase in root tip numbers was observed. Root nodule formation was found retarded and the impaired nodulation was accompanied by a less efficient nitrogen (N) acquisition. The decreased total N content of MtSucS1-antisense lines and an enhanced carbon to N ratio in roots, nodules, and shoots correlated with the extent of MtSucS1 knockdown. On the level of transcription, effects of an MtSucS1 reduction were evident for genes representing important nodes of the nodule carbon and N metabolism, while metabolite profiling revealed significantly lower levels of amino acids and their derivatives particularly in strongly MtSucS1-reduced nodules. Our results support the model that nodule-enhanced Suc synthase 1 of the model legume M. truncatula is required for the establishment and maintenance of an efficient N-fixing symbiosis.

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“…Secondly, the microaerophilic environment necessary for nitrogen fixation is controlled by high‐level expression of leghaemoglobin in the infected nodule cells, which reduces the free‐oxygen concentration in the nitrogen‐fixing zone of the plant nodule to 3–22 nM and is responsible for the pink colour of the plant root nodule (Ott et al ., ; Gibson et al ., ). Thus, the bacterial genes involved in nitrogen fixation are controlled by an oxygen‐sensing two‐component regulatory system, FixJ–FixL (Gong et al ., ), which regulates expression of the nifA gene encoding the master regulator of nitrogen fixation (Dixon & Kahn, ; Gong et al ., ).…”

Section: Differences Between Free‐living Rhizobia and Bacteroidsmentioning

confidence: 99%

Molecular insights into bacteroid development duringRhizobium–legume symbiosis

Haag¹,

Arnold²,

Myka³

et al. 2013

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Rhizobial soil bacteria can form a symbiosis with legumes in which the bacteria fix atmospheric nitrogen into ammonia that can be utilized by the host. The plant, in turn, supplies the rhizobia with a carbon source. After infecting the host cell, the bacteria differentiate into a distinct bacteroid form, which is able to fix nitrogen. The bacterial BacA protein is essential for bacteroid differentiation in legumes producing nodule-specific cysteine-rich peptides (NCRs), which induce the terminal differentiation of the bacteria into bacteroids. NCRs are antimicrobial peptides similar to mammalian defensins, which are important for the eukaryotic response to invading pathogens. The BacA protein is essential for rhizobia to survive the NCR peptide challenge. Similarities in the lifestyle of intracellular pathogenic bacteria suggest that host factors might also be important for inducing chronic infections associated with Brucella abortus and Mycobacterium tuberculosis. Moreover, rhizobial lipopolysaccharide is modified with an unusual fatty acid, which plays an important role in protecting the bacteria from environmental stresses. Mutants defective in the biosynthesis of this fatty acid display bacteroid development defects within the nodule. In this review, we will focus on these key components, which affect rhizobial bacteroid development and survival.

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“…Secondly, the microaerophilic environment necessary for nitrogen fixation is controlled by high-level expression of leghaemoglobin in the infected nodule cells, which reduces the free-oxygen concentration in the nitrogen-fixing zone of the plant nodule to 3-22 nM and is responsible for the pink colour of the plant root nodule (Ott et al, 2005;Gibson et al, 2008). Thus, the bacterial genes involved in nitrogen fixation are controlled by an oxygen-sensing two-component regulatory system, FixJ-FixL (Gong et al, 2006), which regulates expression of the nifA gene encoding the master regulator of nitrogen fixation (Dixon & Kahn, 2004;Gong et al, 2006). The symbiosis between rhizobia and plants is a partnership resulting in the exchange of nutrients between the host cell and the contained bacteroids.…”

Section: Differences Between Free-living Rhizobia and Bacteroidsmentioning

confidence: 99%

Molecular insights into bacteroid development duringRhizobium-legume symbiosis

Haag

¹

,

Arnold

²

,

Myka

³

et al. 2012

View full text Add to dashboard Cite

Rhizobial soil bacteria can form a symbiosis with legumes in which the bacteria fix atmospheric nitrogen into ammonia that can be utilized by the host. The plant, in turn, supplies the rhizobia with a carbon source. After infecting the host cell, the bacteria differentiate into a distinct bacteroid form, which is able to fix nitrogen. The bacterial BacA protein is essential for bacteroid differentiation in legumes producing nodule-specific cysteine-rich peptides (NCRs), which induce the terminal differentiation of the bacteria into bacteroids. NCRs are antimicrobial peptides similar to mammalian defensins, which are important for the eukaryotic response to invading pathogens. The BacA protein is essential for rhizobia to survive the NCR peptide challenge. Similarities in the lifestyle of intracellular pathogenic bacteria suggest that host factors might also be important for inducing chronic infections associated with Brucella abortus and Mycobacterium tuberculosis. Moreover, rhizobial lipopolysaccharide is modified with an unusual fatty acid, which plays an important role in protecting the bacteria from environmental stresses. Mutants defective in the biosynthesis of this fatty acid display bacteroid development defects within the nodule. In this review, we will focus on these key components, which affect rhizobial bacteroid development and survival.

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Sinorhizobium meliloti nifA mutant induces different gene expression profile from wild type in Alfalfa nodules

Cited by 10 publications

References 54 publications

Antisense Repression of the Medicago truncatula Nodule-Enhanced Sucrose Synthase Leads to a Handicapped Nitrogen Fixation Mirrored by Specific Alterations in the Symbiotic Transcriptome and Metabolome

Antisense Repression of the Medicago truncatula Nodule-Enhanced Sucrose Synthase Leads to a Handicapped Nitrogen Fixation Mirrored by Specific Alterations in the Symbiotic Transcriptome and Metabolome

Molecular insights into bacteroid development duringRhizobium–legume symbiosis

Molecular insights into bacteroid development duringRhizobium-legume symbiosis

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