Genetic Organization and Transcriptional Regulation of Rhizobial Nodulation Genes

Schlaman, Helmi R. M.; Phillips, Donald A.; Kondorosi, Éva

doi:10.1007/978-94-011-5060-6_19

Cited by 84 publications

(75 citation statements)

References 224 publications

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“…LYK3 localizes at the plasma membrane and associated vesicles within this zone. The region where NFP and LYK3 accumulate at the cell periphery coincides with the zone where rhizobial Nod genes are active and where, most likely, rhizobia still produce Nod factors (Marie et al, 1994;Schlaman et al, 1998). Therefore, it is very probable that this is the ligand that activates these receptors in the nodule.…”

Section: Discussionmentioning

confidence: 98%

“…The role of Nod factor signaling in epidermal infection and the initial steps of nodule organogenesis is well studied (Geurts and Bisseling, 2002;Oldroyd, 2013). However, inside root nodules, rhizobia still produce Nod factors (Marie et al, 1994;Schlaman et al, 1998), but which process they induce and how they are perceived there is unknown.…”

Section: Introductionmentioning

confidence: 99%

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Nod Factor Receptors Form Heteromeric Complexes and Are Essential for Intracellular Infection inMedicagoNodules

et al. 2014

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Rhizobial Nod factors are the key signaling molecules in the legume-rhizobium nodule symbiosis. In this study, the role of the Nod factor receptors NOD FACTOR PERCEPTION (NFP) and LYSIN MOTIF RECEPTOR-LIKE KINASE3 (LYK3) in establishing the symbiotic interface in root nodules was investigated. It was found that inside Medicago truncatula nodules, NFP and LYK3 localize at the cell periphery in a narrow zone of about two cell layers at the nodule apex. This restricted accumulation is narrower than the region of promoter activity/mRNA accumulation and might serve to prevent the induction of defense-like responses and/or to restrict the rhizobium release to precise cell layers. The distal cell layer where the receptors accumulate at the cell periphery is part of the meristem, and the proximal layer is part of the infection zone. In these layers, the receptors can most likely perceive the bacterial Nod factors to regulate the formation of symbiotic interface. Furthermore, our Förster resonance energy transfer-fluorescence lifetime imaging microscopy analysis indicates that NFP and LYK3 form heteromeric complexes at the cell periphery in M. truncatula nodules.

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Section: Discussionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Nod Factor Receptors Form Heteromeric Complexes and Are Essential for Intracellular Infection inMedicagoNodules

et al. 2014

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“…Interestingly, the gene is associated with nodulation genes, which are under the control of a nod box promoter. The nod box is the binding site of NodD, a LysR-type regulator, which activates nodulation genes in the presence of flavonoids (33). In a recent comprehensive study of S. meliloti strain 1021, genes encoding efflux systems belonging to different families were analyzed (5).…”

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confidence: 99%

Characterization of the Flavonoid-Responsive Regulator FrrA and Its Binding Sites

et al. 2012

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Previous microarray analyses revealed that in Bradyrhizobium japonicum, about 100 genes are induced by genistein, an isoflavonoid secreted by soybean. This includes the three genes freC, freA, and freB (systematic designations bll4319, bll4320, and bll4321), which are likely to form a genistein-, daidzein-, and coumestrol-inducible operon and to encode a multidrug efflux system. Upstream of freCAB and in the opposite orientation, FrrA (systematic designation Blr4322), which has similarity to TetRtype regulators, is encoded. A deletion of frrA leads to increased expression of freB in the absence of an inducer. We identified the correct translational start codon of frrA and showed that the gene is inducible by genistein and daidzein. The protein, which was heterologously expressed and purified from Escherichia coli, binds to two palindrome-like DNA elements (operator A and operator B), which are located in the intergenic region between freC and frrA. The replacement of several nucleotides or the insertion of additional spacer nucleotides prevented binding. Binding of FrrA was also affected by the addition of genistein. By mapping the transcription start sites, we found that operator A covers the transcriptional start site of freC and operator B is probably located between the ؊35 regions of the two divergently oriented genes. Operator A seems to be conserved in a few similar gene constellations in other proteobacteria. Our data indicate that in B. japonicum, besides NodD1 (the LysR family) and NodVW (a two-component response regulator), a third regulator type (a TetR family member) which responds to the plant signal molecules genistein and daidzein exists.

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“…Most of the previously characterized genes on pSymA had been identified by using classical bacterial genetics to search for genes required for formation of nitrogen-fixing nodules on alfalfa. Clustered within a 275-kb region, these include nod genes required for synthesis of Nod factor as well as the nol and noe genes, which are encoded in six operons on pSymA (9). nodD1, nodD2, and nodD3 encode LysR-type transcriptional regulators that activate expression of these operons in response to plant signals or as part of signal-independent regulatory circuitry (10).…”

mentioning

confidence: 99%

Nucleotide sequence and predicted functions of the entire Sinorhizobium meliloti pSymA megaplasmid

Barnett

Fisher

Jones

et al. 2001

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

282

227

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The symbiotic nitrogen-fixing soil bacterium Sinorhizobium meliloti contains three replicons: pSymA, pSymB, and the chromosome. We report here the complete 1,354,226-nt sequence of pSymA. In addition to a large fraction of the genes known to be specifically involved in symbiosis, pSymA contains genes likely to be involved in nitrogen and carbon metabolism, transport, stress, and resistance responses, and other functions that give S. meliloti an advantage in its specialized niche.

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Genetic Organization and Transcriptional Regulation of Rhizobial Nodulation Genes

Cited by 84 publications

References 224 publications

Nod Factor Receptors Form Heteromeric Complexes and Are Essential for Intracellular Infection inMedicagoNodules

Nod Factor Receptors Form Heteromeric Complexes and Are Essential for Intracellular Infection inMedicagoNodules

Characterization of the Flavonoid-Responsive Regulator FrrA and Its Binding Sites

Nucleotide sequence and predicted functions of the entire Sinorhizobium meliloti pSymA megaplasmid

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