Organization, structure and symbiotic function of rhizobium meliloti nodulation genes determining host specificity for alfalfa

Horváth, Beatrix; Kondorosi, Éva; John, Michael; Schmidt, Jürgen; Török, I.; Györgypál, Zoltán; Barabás, Ilona; Wieneke, Ursula; Schell, Jeff; Kondorosi, Ádám

doi:10.1016/0092-8674(86)90654-9

Cited by 186 publications

(118 citation statements)

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“…pIN-II-A2, ApR, 3.5 kb 1291 [29] obtained without added DNA, also increased threefold. A temperature of 30°C was, therefore, chosen for our measurements.…”

Section: Resultsmentioning

confidence: 75%

“…When the Tn5-mutated fragment was homogenotized back into the wild-type genome of R. meliloti, the mutant derivative exhibited an increased sensitivity to methyl methanesulfonate and to ultraviolet light as compared to the wild-type bacteria, indicating that the mutation abolished a function of the recA product (data not shown). Since Tn5 insertions do not show a strong polar effect in R. meliloti [29,361, it is likely that the 41-kDa protein is the product of a recA-homologous gene.…”

Section: Resultsmentioning

confidence: 99%

“…In R. meliloti 41 a 6.8-kb EcoRI fragment, determining host-range specificity, was identified. The hsn fragment was physically mapped and the exact position of the proteincoding regions-was determined usingdifferent methods, which will be published elsewhere [29].…”

Section: Expression Of 'Common' Nodulation Genes In the R Meliloti mentioning

confidence: 99%

“…The following plasmids were used for cloning: pBR322 [27] and pBR325 [28]. Other recombinant plasmids are described [8] or were constructed by Horvath et al [29]. E. Cali strain HBlOl was transformed with recombinant plasmids [30].…”

Section: Molecular Cloningmentioning

confidence: 99%

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A cell‐free system from Rhizobium meliloti to study the specific expression of nodulation genes

Dusha

Schröder

Putnoky

et al. 1986

European Journal of Biochemistry

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An in vitro transcription-translation system was developed using cell-free extracts from the symbiotic nitrogenfixing bacterium Rhizobium meliloti strain 41. Conditions for preparation of the 30000 x g supernatant extract and for measurement of protein-synthesizing activity were determined and compared to the activity of an Eschericha coli cell-free system. Genes expressed in the free-living or in the symbiotic state were studied. The product of a recA-like gene (41-kDa protein) was synthesized both in R. meliloti and E. coli extracts, although less efficiently in the heterologous system. In agreement with earlier results obtained in E. coli minicells, three proteins (44, 28.5 and 23 kDa) were synthesized from a cloned 3.3 x 103-base DNA region carrying genes for nodulation (nod). However, differences in the transcription-translation of nod and host specificity (hsn) genes were observed when protein expression was compared in R. meliloti and E. coli cell-free extracts, and the possible explanations of these findings are discussed.Rhizobium meliloti, a member of the family Rhizobiaceae, is able to establish a symbiotic relationship with leguminous plants. As a result of the interaction of plant and bacterial genes, root nodules are formed which are able to fix atmospheric nitrogen.Bacterial genes required for nodule formation have been identified in R . meliloti. The nodulation genes, described so far, are located on a large plasmid and are closely linked to nif genes [I -51. Nodulation genes are arranged into two clusters: early nodulation functions, which are conserved in many Rhizobium species, form one cluster ('common' nod genes) [4,6, 71 were reported. To explain the lack or decreased level of protein synthesis from some heterologous DNA templates in the E. coli system, differences in sequence signals involved in transcription and translation processes were invoked. Recently we published the observation that SmR of transposon Tn5 is expressed in vivo in R. meliloti although it is not detectable in E. coli [20]. This finding also supports the idea that differences either on the transcriptional or translational level or both between the two species may exist. To circumvent these difficulties our aim was to establish an in vitro proteinsynthesizing system from R. meliloti, which would enable us to study specific expression of Rhizobium genes. MATERIALS AND METHODS Preparation of R. meliloti cellqree extractStrain AK631, a prototrophic, symbiotically effective derivative of R. meliloti 41 with compact colony morphology, was used for preparation of the 30000 x g supernatant (S-30) extract. Cells were grown with shaking at 170 rpm at 32°C in TY medium [21] to A600 = 0.7-1.0. Cultures were cooled rapidly in an ice/water bath and cells were collected by centrifugation at 6000 rpm for 20 min at 4°C. The bacterial pellet was washed twice with buffer A containing 20 mM Trislacetate (pH 8.2), 10 mM magnesium acetate, 40 mM potassium acetate, 1 mM dithiothreitol. Bacteria were stored at -20°C until used. For the prepara...

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“…pIN-II-A2, ApR, 3.5 kb 1291 [29] obtained without added DNA, also increased threefold. A temperature of 30°C was, therefore, chosen for our measurements.…”

Section: Resultsmentioning

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Section: Expression Of 'Common' Nodulation Genes In the R Meliloti mentioning

confidence: 99%

Section: Molecular Cloningmentioning

confidence: 99%

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A cell‐free system from Rhizobium meliloti to study the specific expression of nodulation genes

Dusha

Schröder

Putnoky

et al. 1986

European Journal of Biochemistry

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“…For example, nitrogen-fixing nodules account for one quarter of total nitrogen fixed globally each year (3). The development of nitrogen-fixing nodules by rhizobia involves a variety of interactions between the plant and microbe; however, at the center of this process are a set of nod (nodulation) genes required for the synthesis of oligosaccharide-nodulation factors, for determining host-plant specificity, and for optimizing the efficiency of symbiosis (4)(5)(6). Successful interaction between the rhizobium and host plant requires expression of both positive and negative transcriptional control of genes related to nodulation and symbiosis (7,8).…”

mentioning

confidence: 99%

Structural basis for regulation of rhizobial nodulation and symbiosis gene expression by the regulatory protein NolR

Lee

Krishnan

Jez

2014

Proc. Natl. Acad. Sci. U.S.A.

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The symbiosis between rhizobial microbes and host plants involves the coordinated expression of multiple genes, which leads to nodule formation and nitrogen fixation. As part of the transcriptional machinery for nodulation and symbiosis across a range of Rhizobium, NolR serves as a global regulatory protein. Here, we present the X-ray crystal structures of NolR in the unliganded form and complexed with two different 22-base pair (bp) double-stranded operator sequences (oligos AT and AA). Structural and biochemical analysis of NolR reveals protein-DNA interactions with an asymmetric operator site and defines a mechanism for conformational switching of a key residue (Gln56) to accommodate variation in target DNA sequences from diverse rhizobial genes for nodulation and symbiosis. This conformational switching alters the energetic contributions to DNA binding without changes in affinity for the target sequence. Two possible models for the role of NolR in the regulation of different nodulation and symbiosis genes are proposed. To our knowledge, these studies provide the first structural insight on the regulation of genes involved in the agriculturally and ecologically important symbiosis of microbes and plants that leads to nodule formation and nitrogen fixation.transcription factor | protein structure T he symbiosis between rhizobial bacteria from the Rhizobium, Sinorhizobium, Mesorhizobium, Azorhizobium, and Bradyrhizobium genera and leguminous plants leads to the formation of root nodules (1, 2). These plant organs are specialized for nitrogen fixation and assimilation and are of major ecological and agricultural importance. For example, nitrogen-fixing nodules account for one quarter of total nitrogen fixed globally each year (3). The development of nitrogen-fixing nodules by rhizobia involves a variety of interactions between the plant and microbe; however, at the center of this process are a set of nod (nodulation) genes required for the synthesis of oligosaccharide-nodulation factors, for determining host-plant specificity, and for optimizing the efficiency of symbiosis (4-6). Successful interaction between the rhizobium and host plant requires expression of both positive and negative transcriptional control of genes related to nodulation and symbiosis (7,8

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Host-specific regulation of nodulation genes in Rhizobium is mediated by a plant-signal, interacting with the nodD gene product

et al. 1987

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We have identified a nodD gene from the wide host‐range Rhizobium strain MPIK3030 (termed nodD1) which is essential for nodulation on Macroptilium atropurpureum (siratro). Experiments with nodA–lacZ gene fusions demonstrate that the MPIK3030 nodD1 regulates expression of the nodABC genes. Additionally, we used nodC–lacZ fusions of Rhizobium meliloti to show that the MPIK3030 nodD1 gene induces expression of these fusions by interacting with plant factors from siratro and from the non‐host Medicago sativa (alfalfa). The R. meliloti nodD genes, however, only interact with alfalfa exudate. In line with these results, no complementation of MPIK3030 nodD1 mutants could be obtained on siratro with the R. meliloti nodD genes, while the MPIK3030 nodD1 can complement nodD mutants of R. meliloti on alfalfa. Furthermore, R. meliloti transconjugants harbouring the MPIK3030 nodD1 efficiently nodulate the illegitimate host siratro. When compared with other nodD sequences, the amino acid sequence of the MPIK3030 nodD1 shows a conserved aminoterminus, whereas the carboxy‐terminus of the putative gene product diverges considerably. Studies on a chimeric MPIK3030/R. meliloti nodD gene indicates that the carboxy‐terminal region is responsible for the interaction with plant factor(s) and may have evolved in different rhizobia specifically to interact with plant–host factors.

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Organization, structure and symbiotic function of rhizobium meliloti nodulation genes determining host specificity for alfalfa

Cited by 186 publications

References 33 publications

A cell‐free system from Rhizobium meliloti to study the specific expression of nodulation genes

A cell‐free system from Rhizobium meliloti to study the specific expression of nodulation genes

Structural basis for regulation of rhizobial nodulation and symbiosis gene expression by the regulatory protein NolR

Host-specific regulation of nodulation genes in Rhizobium is mediated by a plant-signal, interacting with the nodD gene product

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