scholarly journals Rhizobium fix genes mediate at least two communication steps in symbiotic nodule development.

1988 ◽  
Vol 106 (3) ◽  
pp. 597-607 ◽  
Author(s):  
P Putnoky ◽  
E Grosskopf ◽  
D T Ha ◽  
G B Kiss ◽  
A Kondorosi
Keyword(s):  
Rhizobium Meliloti ◽  
Host Cells ◽  
Nodule Development ◽  
Peribacteroid Membrane ◽  
Symbiotic Gene ◽  
Morphological Studies ◽  
Group I ◽  
Infection Threads ◽  
Symbiotic Nodule ◽  
Bacterial Genes

To identify bacterial genes involved in symbiotic nodule development, ineffective nodules of alfalfa (Medicago sativa) induced by 64 different Fix-mutants of Rhizobium meliloti were characterized by assaying for symbiotic gene expression and by morphological studies. The expression of leghemoglobin and nodulin-25 genes from alfalfa and of the nifHD genes from R. meliloti were monitored by hybridizing the appropriate DNA probes to RNA samples prepared from nodules. The mutants were accordingly divided into three groups. In group I none of the genes were expressed, in group II only the plant genes were expressed and in group III all three genes were transcribed. Light and electron microscopical analysis of nodules revealed that nodule development was halted at different stages in nodules induced by different group I mutants. In most cases nodules were empty lacking infection threads and bacteroids or nodules contained infection threads and a few released bacteroids. In nodules induced by a third mutant class bacteria were released into the host cells, however the formation of the peribacteroid membrane was not normal. On this basis we suggest that peribacteroid membrane formation precedes leghemoglobin and nodulin-25 induction, moreover, after induction of nodulation by the nod genes at least two communication steps between the bacteria and the host plants are necessary for the development of the mature nodule. By complementing each mutant of group I with a genomic R. meliloti library made in pLAFRl, four new fix loci were identified, indicating that several bacterial genes are involved in late nodule development.

scholarly journals ANALYSIS OF INTERACTION OF PEA (Pisum sativum L.) SYMBIOTIC GENES Sym33 AND Sym42 WHOSE MUTATIONS RESULT IN ABNORMALITES DURING INFECTION THREAD DEVELOPMENT

2012 ◽  
Vol 10 (4) ◽  
pp. 50-55
Author(s):  
Viktor E Tsyganov ◽  
Anna V Tsyganova ◽  
Vera A Voroshilova ◽  
Aleksey U Borisov ◽  
Igor A Tikhonovich
Keyword(s):  
Pisum Sativum ◽  
Mutant Allele ◽  
Double Mutant ◽  
Nodule Development ◽  
Symbiotic Genes ◽  
Pisum Sativum L ◽  
Infection Threads ◽  
Gene Functions ◽  
Symbiotic Nodule ◽  
Mutant Lines

Using pea single mutant lines SGEFix–-2 (sym33) and RisFixV (sym42), which are characterized by different abnormalities during symbiotic nodule development, including thickening of infection threads’ walls, a double mutant RBT4 line, carrying a pair of symbiotic genes sym33 and sym42 was constructed. The epistasis of the mutant allele sym33 over the mutant allele sym42 with respect to the histological and ultrastructural organisation of nodules was shown. Thus, it was demonstrated that Sym33 gene functions earlier in symbiotic nodule development than Sym42 gene.

scholarly journals Morphology of root nodules and nodule-like structures formed by Rhizobium and Agrobacterium strains containing a Rhizobium meliloti megaplasmid.

1983 ◽  
Vol 97 (3) ◽  
pp. 787-794 ◽  
Author(s):  
C H Wong ◽  
C E Pankhurst ◽  
A Kondorosi ◽  
W J Broughton
Keyword(s):  
Normal Development ◽  
Rhizobium Meliloti ◽  
Root Nodules ◽  
Root Hairs ◽  
Host Cells ◽  
Donor Strain ◽  
Intercellular Spaces ◽  
Infection Threads ◽  
Infected Cells ◽  
Rhizobium Sp

We examined expression of the megaplasmid pRme41b of Rhizobium meliloti in two different Rhizobium sp. Strains and in Agrobacterium tumefaciens. Transfer of pRme41b into these bacteria was facilitated by insertion of a recombinant plasmid coding for mobilization functions of RP4 into the nif region (Kondorosi, A., E. Kondorosi, C.E. Pankhurst, W. J. Broughton, and Z. Banfalvi, 1982, Mol. Gen. Genet., 188:433-439). In all cases, transconjugants formed nodule-like structures on the roots of Medicago sativa. These structures were largely composed of meristematic cells but they were not invaded by bacteria. Bacteria were found only within infection threads in root hairs, and within intercellular spaces of the outermost cells of the structures. The donor strain of R. meliloti containing pAK11 or pAK12 in pRme41b initially produced nodules on M. sativa that did not fix nitrogen (Fix-). In these nodules, bacteria were released from infection threads into the host cells but they did not multiply appreciably. Any bacteroids formed degenerated prematurely. In some cases, however, reversion to a Fix+ phenotype occurred after 4 to 6 wk. Bacteria released into newly infected cells in these nodules showed normal development into bacteriods.

scholarly journals Double Mutant Analysis of Sequential Functioning of Pea (Pisum sativum L.) Genes: Sym13, Sym33 and Sym40 During Symbiotic Nodule Development

2010 ◽  
Vol 8 (2) ◽  
pp. 3-8 ◽  
Author(s):  
Viktor E Tsyganov ◽  
Elena V Seliverstova ◽  
Vera A Voroshilova ◽  
Anna V Tsyganova ◽  
Zlata B Pavlova ◽  
...  
Keyword(s):  
Pisum Sativum ◽  
Mutant Allele ◽  
Double Mutant ◽  
Developmental Stages ◽  
Infection Process ◽  
Nodule Development ◽  
Symbiotic Gene ◽  
Mutant Analysis ◽  
Pisum Sativum L ◽  
Symbiotic Nodule

Two double mutants carrying pea symbiotic gene pairs sym13, sym40 and sym33, sym40, respectively, were constructed using single mutants blocked at different nodule developmental stages: E135f (sym13), SGEFix–‑1 (sym40) and SGEFix–‑2 (sym33). The epistasis of the mutant allele sym40 over the mutant allele sym13 and sym33 over sym40 was shown with respect to nodule histological and ultrastructural organisation. Thus, the proposed earlier sequential functioning of genes during infection process: Sym33→Sym40→Sym13 has been confirmed. 

scholarly journals Ectopic Expression of the Rhizobium etli amtB Gene Affects the Symbiosome Differentiation Process and Nodule Development

1999 ◽  
Vol 12 (6) ◽  
pp. 515-525 ◽  
Author(s):  
Rosarita Taté ◽  
Michele Cermola ◽  
Anna Riccio ◽  
Maurizio Iaccarino ◽  
Mike Merrick ◽  
...  
Keyword(s):  
Nitrogenase Activity ◽  
Ectopic Expression ◽  
Host Cells ◽  
Nodule Development ◽  
Differentiation Process ◽  
Symbiotic Interaction ◽  
Methylammonium Transport ◽  
Bacterial Genes

Under conditions of nitrogen limitation, soil bacteria of the genus Rhizobium are able to induce the development of symbiotic nodules on the roots of leguminous plants. During nodule organogenesis, bacteria are released endocytotically inside the invaded plant cells where they differentiate into their endosymbiotic form called bacteroids. Bacteroids surrounded by a plant-derived peribacteroid membrane are nondividing, organelle-like structures, called symbiosomes, that use nitrogenase to reduce N2 to ammonia. Experiments performed in vitro with isolated symbiosomes have previously led to the suggestion that the NH3 produced by the bacteroids is released as NH4+ into the plant cytosol. Furthermore, it was observed that the bacterial amtB (ammonium/methylammonium transport B) gene is switched off very early during symbiosis, just when bacteria are released into the host cells. We report here that the ectopic expression of amtB in bacteroids alters the ability of bacteria to invade the host cells and the symbiosome differentiation process. Both the NtrC protein, which controls the expression of the bacterial genes involved in NH4+ assimilation, and the nitrogenase activity are essential to observe the amtB-mediated effect. Our results support the idea that in vivo bacteroids do not take up NH4+ and demonstrate that the transcriptional down-regulation of the amtB gene is essential for an effective symbiotic interaction.

Ultrastructure of root nodules formed by ineffective strains of Rhizobium meliloti

1974 ◽  
Vol 20 (5) ◽  
pp. 755-758 ◽  
Author(s):  
C. R. MacKenzie ◽  
D. C. Jordan
Keyword(s):  
Rhizobium Meliloti ◽  
Root Nodules ◽  
Plant Cells ◽  
Host Cells ◽  
Nodule Development ◽  
Nodule Formation ◽  
Starch Granules ◽  
Naturally Occurring ◽  
Intimate Association ◽  
Rough Er

In three ineffective associations between Medicago sativa (alfalfa) and Rhizobium meliloti the initial stages of nodule formation, resulting in the release of the bacteria into the host cells, were found to follow the normal pattern of nodule development. In nodule tissue formed by two laboratory-produced ineffective mutants, a rapid disintegration of the invading bacteria was observed to occur shortly after the release of the bacteria into the plant cells. The disintegrating bacteria were in intimate association with large amounts of rough endoplasmic reticulum (ER). An increase in the number of mitochondria occurred at this stage as well and the peripheries of the plant cells were often lined with starch granules. Only occasionally was the stage of enclosing-membrane formation reached. In the third ineffective association, a naturally occurring one, the bacteria were transformed into the nitrogen-fixing or bacteroidal forms and were surrounded by enclosing membranes. Dissolution of the bacteria occurred at a slightly later stage in this association and was again accompanied by a buildup of rough ER. Evidence is presented to suggest that the plant response, as characterized by this ER buildup in these ineffective associations, was a manifestation of nitrogen starvation.

Symbiotic gene probes hybridize to cryptic plasmids of indigenous Rhizobium meliloti

1988 ◽  
Vol 34 (5) ◽  
pp. 703-707 ◽  
Author(s):  
L. R. Barran ◽  
E. S. P. Bromfield
Keyword(s):  
Dna Sequences ◽  
Rhizobium Meliloti ◽  
Dna Probes ◽  
Cryptic Plasmid ◽  
Nodule Development ◽  
Nif Genes ◽  
Symbiotic Gene ◽  
Gene Probes ◽  
Cryptic Plasmids

DNA probes for host specific nodulation (hsn) common nodulation (nod), exopolysaccharide (exo), nodule development (ndv) and nitrogenase structural (nif) genes were used to examine a collection of symbiotically effective, genotypically distinct isolates of indigenous Rhizobium meliloti for reiteration of symbiotic DNA sequences on cryptic plasmids. Nineteen of 30 isolates possessed at least one cryptic plasmid with reiterated DNA sequences, and of these isolates 15, 5, and 1 contained cryptic plasmids that hybridized to hsn, nif, and nod gene probes respectively; both hsn and nif probes hybridized to a single cryptic plasmid in each of two isolates. The exo and ndv probes did not hybridize to cryptic plasmids in any of the 30 isolates of R. meliloti.

scholarly journals Novel rkp Gene Clusters ofSinorhizobium meliloti Involved in Capsular Polysaccharide Production and Invasion of the Symbiotic Nodule: the rkpKGene Encodes a UDP-Glucose Dehydrogenase

1998 ◽  
Vol 180 (20) ◽  
pp. 5426-5431 ◽  
Author(s):  
Attila Kereszt ◽  
Ernő Kiss ◽  
Bradley L. Reuhs ◽  
Russell W. Carlson ◽  
Ádám Kondorosi ◽  
...  
Keyword(s):  
Sinorhizobium Meliloti ◽  
Capsular Polysaccharide ◽  
Rhizobium Meliloti ◽  
Glucose Dehydrogenase ◽  
Attachment Site ◽  
Gene Clusters ◽  
Protein Product ◽  
Infection Process ◽  
Nodule Development ◽  
Symbiotic Nodule

ABSTRACT The production of exopolysaccharide (EPS) was shown to be required for the infection process by rhizobia that induce the formation of indeterminate nodules on the roots of leguminous host plants. InSinorhizobium meliloti (also known as Rhizobium meliloti) Rm41, a capsular polysaccharide (KPS) analogous to the group II K antigens of Escherichia coli can replace EPS during symbiotic nodule development and serve as an attachment site for the strain-specific bacteriophage φ16-3. The rkpA to -J genes in the chromosomal rkp-1 region code for proteins that are involved in the synthesis, modification, and transfer of an as-yet-unknown lipophilic molecule which might function as a specific lipid carrier during KPS biosynthesis. Here we report that with a phage φ16-3-resistant population obtained after random Tn5 mutagenesis, we have identified novel mutants impaired in KPS production by genetic complementation and biochemical studies. The mutations represent two novel loci, designated therkp-2 and rkp-3 regions, which are required for the synthesis of rhizobial KPS. The rkp-2 region harbors two open reading frames (ORFs) organized in monocistronic transcription units. Although both genes are required for normal lipopolysaccharide production, only the second one, designated rkpK, is involved in the synthesis of KPS. We have demonstrated that RkpK possesses UDP-glucose dehydrogenase activity, while the protein product of ORF1 might function as a UDP-glucuronic acid epimerase.

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