Expression of the nodulation and nitrogen fixation genes in Rhizobium meliloti during development

Genome ◽  
1989 ◽  
Vol 31 (1) ◽  
pp. 354-360 ◽  
Author(s):  
San Chiun Shen ◽  
Shui Ping Wang ◽  
Guan Qiao Yu ◽  
Jia Bi Zhu
Keyword(s):  
Nitrogen Fixation ◽  
Rhizobium Meliloti ◽  
Abnormal Development ◽  
Wild Type ◽  
Free Living ◽  
Nod Genes ◽  
Nodule Initiation ◽  
Fix Genes ◽  
Nitrogen Fixation Genes

Genes that specify nodulation (nod genes) are only active in the free-living rhizobia or in the nodule initiation state of rhizobia. As soon as the repression of nod genes occurs in the bacteroids of the nodule, nifA is induced, while ntrC is inactivated and thus the nifA-mediated nif/fix genes are turned on. Limitation of available oxygen brings about the induction of nifA, which reflects the actual status of nif/fix gene activities in symbiotic state of rhizobia. Oxygen thus appears to be a major symbiotic signal to the expression of bacteroid nif/fix genes. Mutation of nifA or shortage of nifA product in wild-type rhizobia caused by the inhibition of multicopy nifH/fixA promoters leads to an abnormal development of nodules and premature degradation of bacteroids in nodules.Key words: nitrogen fixation, nodulation, nif/fix regulation, nifA mutant.

scholarly journals The Effect of Exogenous Nitrate on LCO Signalling, Cytokinin Accumulation, and Nodule Initiation in Medicago truncatula

Genes ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 988
Author(s):  
Kerstin Gühl ◽  
Rens Holmer ◽  
Ting Ting Xiao ◽  
Defeng Shen ◽  
Titis A. K. Wardhani ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Medicago Truncatula ◽  
Potent Inhibitor ◽  
Ethylene Biosynthesis ◽  
Wild Type ◽  
Biosynthesis Inhibitor ◽  
Signalling Molecules ◽  
Nodule Initiation

Nitrogen fixation by rhizobia is a highly energy-demanding process. Therefore, nodule initiation in legumes is tightly regulated. Environmental nitrate is a potent inhibitor of nodulation. However, the precise mechanism by which this agent (co)regulates the inhibition of nodulation is not fully understood. Here, we demonstrate that in Medicago truncatula the lipo-chitooligosaccharide-induced accumulation of cytokinins is reduced in response to the application of exogenous nitrate. Under permissive nitrate conditions, perception of rhizobia-secreted signalling molecules leads to an increase in the level of four cytokinins (i.e., iP, iPR, tZ, and tZR). However, under high-nitrate conditions, this increase in cytokinins is reduced. The ethylene-insensitive mutant Mtein2/sickle, as well as wild-type plants grown in the presence of the ethylene biosynthesis inhibitor 2-aminoethoxyvinyl glycine (AVG), is resistant to the inhibition of nodulation by nitrate. This demonstrates that ethylene biosynthesis and perception are required to inhibit nodule organogenesis under high-nitrate conditions.

scholarly journals Novel European free-living, non-diazotrophic Bradyrhizobium isolates from contrasting soils that lack nodulation and nitrogen fixation genes – a genome comparison

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Frances Patricia Jones ◽  
Ian M. Clark ◽  
Robert King ◽  
Liz J. Shaw ◽  
Martin J. Woodward ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Genome Comparison ◽  
Free Living ◽  
A Genome ◽  
Nitrogen Fixation Genes

Mobilization of a Rhizobium meliloti megaplasmid carrying nodulation and nitrogen fixation genes into other rhizobia and Agrobacterium

1982 ◽  
Vol 188 (3) ◽  
pp. 433-439 ◽  
Author(s):  
A. Kondorosi ◽  
E. Kondorosi ◽  
C. E. Pankhurst ◽  
W. J. Broughton ◽  
Z. Banfalvi
Keyword(s):  
Nitrogen Fixation ◽  
Rhizobium Meliloti ◽  
Nitrogen Fixation Genes

scholarly journals Symbiotic Burkholderia Species Show Diverse Arrangements of nif/fix and nod Genes and Lack Typical High-Affinity Cytochrome cbb3 Oxidase Genes

2016 ◽  
Vol 29 (8) ◽  
pp. 609-619 ◽  
Author(s):  
Sofie E. De Meyer ◽  
Leah Briscoe ◽  
Pilar Martínez-Hidalgo ◽  
Christina M. Agapakis ◽  
Paulina Estrada de-los Santos ◽  
...  
Keyword(s):  
16S Rrna ◽  
Gene Sequencing ◽  
Genomic Analysis ◽  
16S Rrna Gene Sequencing ◽  
Rrna Gene ◽  
Free Living ◽  
Nod Genes ◽  
Electron Transport Chains ◽  
Rrna Gene Sequencing ◽  
Fix Genes

Genome analysis of fourteen mimosoid and four papilionoid beta-rhizobia together with fourteen reference alpha-rhizobia for both nodulation (nod) and nitrogen-fixing (nif/fix) genes has shown phylogenetic congruence between 16S rRNA/MLSA (combined 16S rRNA gene sequencing and multilocus sequence analysis) and nif/fix genes, indicating a free-living diazotrophic ancestry of the beta-rhizobia. However, deeper genomic analysis revealed a complex symbiosis acquisition history in the beta-rhizobia that clearly separates the mimosoid and papilionoid nodulating groups. Mimosoid-nodulating beta-rhizobia have nod genes tightly clustered in the nodBCIJHASU operon, whereas papilionoid-nodulating Burkholderia have nodUSDABC and nodIJ genes, although their arrangement is not canonical because the nod genes are subdivided by the insertion of nif and other genes. Furthermore, the papilionoid Burkholderia spp. contain duplications of several nod and nif genes. The Burkholderia nifHDKEN and fixABC genes are very closely related to those found in free-living diazotrophs. In contrast, nifA is highly divergent between both groups, but the papilionoid species nifA is more similar to alpha-rhizobia nifA than to other groups. Surprisingly, for all Burkholderia, the fixNOQP and fixGHIS genes required for cbb3 cytochrome oxidase production and assembly are missing. In contrast, symbiotic Cupriavidus strains have fixNOQPGHIS genes, revealing a divergence in the evolution of two distinct electron transport chains required for nitrogen fixation within the beta-rhizobia.

Synthesis of the ferredoxin-like protein FdxN from Rhizobium meliloti bacteroids as a fusion protein in Escherichia coli

1992 ◽  
Vol 38 (6) ◽  
pp. 534-540 ◽  
Author(s):  
Kai-Uwe Riedel ◽  
Bernd Masepohl ◽  
Werner Klipp ◽  
Alfred Pühler
Keyword(s):  
Escherichia Coli ◽  
Fusion Proteins ◽  
Symbiotic Nitrogen Fixation ◽  
Rhizobium Meliloti ◽  
Wild Type ◽  
Free Living ◽  
T7 Promoter ◽  
E Coli ◽  
Stabilizing Factors ◽  
Transcriptional Fusions

To analyze the overexpression of the Rhizobium meliloti fdxN gene in Escherichia coli, different translational and transcriptional fusions were constructed. The translational signals of R. meliloti fdxN were recognized in E. coli as demonstrated by the use of in-frame lac fusions. Translational fusions consisting of the lacZ or the lpp gene fused in frame to the 3′ end of the entire fdxN gene were expressed at high levels in E. coli. In contrast, the wild-type R. meliloti FdxN protein without a C-terminal fusion could only be detected using the very sensitive T7 promoter–polymerase system and not in immunoblots with antibodies against an FdxN–LacZ hybrid protein. Evidently, translational fusions to the 3′ end of fdxN had a stabilizing effect on the expression of the fdxN gene. A constitutively expressed transcriptional fdxN fusion, which did not mediate detectable amounts of FdxN protein either in E. coli or in free-living R. meliloti cells, complemented the Fix− phenotype of an R. meliloti fdxN::[Tc] mutant strain to wild-type levels. Therefore, either low amounts of the wild-type FdxN protein are sufficient for symbiotic nitrogen fixation or there are stabilizing factors, which are present only in R. meliloti bacteroids but not in free-living R. meliloti cells. Fusion proteins consisting of FdxN and LacZ or a partial Lpp protein restored the Fix− phenotype of an R. meliloti fdxN mutant to 3 and 11%, respectively, indicating that a C-terminal fusion did not completely abolish the function of FdxN. Key words: overexpression, protein stability, immunoblot, complementation.

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