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.

Formation and structure of root nodules induced on Macroptilium atropurpureum inoculated with various species of Rhizobium

1991 ◽  
Vol 69 (7) ◽  
pp. 1520-1532 ◽  
Author(s):  
Michael J. Trinick ◽  
Celia Miller ◽  
Paul A. Hadobas
Keyword(s):  
Rhizobium Leguminosarum ◽  
Rhizobium Meliloti ◽  
Root Nodules ◽  
Matrix Material ◽  
Immunogold Labelling ◽  
Infection Threads ◽  
Glass Tubes ◽  
Infected Cells ◽  
Macroptilium Atropurpureum ◽  
Nodule Tissue

Fifteen strains of Rhizobium leguminosarum biovar trifolii formed ineffective nodules and (or) nodule-like structures (rhizobia were re-isolated from both structures) on Macroptilium atropurpureum grown in enclosed glass tubes. Bacteria were observed among the parenchyma cells surrounding the nodule-like structures. One variant of R. leguminosarum biovar trifolii (NGR66/ST) isolated from M. atropurpureum formed nodules on this host that exhibited abnormal intercellular and intracellular infection. The bacteria (NGR66/ST) were contained within threadlike structures, surrounded by matrix material. The identities of the Rhizobium strains were confirmed serologically after reisolation and in sections of nodule tissue using immunogold labelling. Rhizobium leguminosarum biovar phaseoli strain NGR76 isolated from Phaseolus vulgaris formed nodules on M. atropurpureum resembling those formed by effective Bradyrhizobium strains. The association was partially effective in nitrogen fixation, and this was reflected in the nodule structure. The percentage of cells infected was lower than that in fully effective nodules. There was a high frequency of infected cells showing degeneration; these were located throughout the nodule tissue and were often adjacent to healthy infected cells. The rhizobia appeared to infect new nodule cells via infection threads, which were abundant both intercellularly and intracellularly in young, mature, and degenerating host nodule cells. Strains of R. leguminosarum biovar viceae and Rhizobium meliloti were unable to induce nodule-like structures on M. atropurpureum. Key words: Macroptilium, Bradyrhizobium, Rhizobium, microscopy, nodule, structure.

The occurrence of infected cells, with persistent infection threads, in legume root nodules

1987 ◽  
Vol 65 (3) ◽  
pp. 553-558 ◽  
Author(s):  
Sergio M. de Faria ◽  
Shona G. McInroy ◽  
Janet I. Sprent
Keyword(s):  
Root Nodules ◽  
Root Hairs ◽  
Infection Process ◽  
Wall Material ◽  
Cell Wall Material ◽  
Legume Trees ◽  
Infection Threads ◽  
Host Cell Wall ◽  
Infected Cells ◽  
Intercellular Spread

A survey of the structure of nodules from primitive legume trees was conducted. All genera examined in the subfamily Caesalpinioideae, some from the Papilionoideae, but none from the Mimosoideae had cells in the central, nitrogen-fixing region in which bacteria were confined by host cell wall material in structures resembling infection threads. However, infection of these cells occurred by intercellular spread of rhizobia rather than by infection threads. It is suggested that infection threads may have evolved in infected cells and later extended to early stages of the infection process including entry into root hairs.

A light and electron microscope study of the fungal endophytes in the sporophyte and gametophyte of Lycopodium cernuum with observations on the gametophyte–sporophyte junction

1992 ◽  
Vol 70 (1) ◽  
pp. 58-72 ◽  
Author(s):  
Jeffrey G. Duckett ◽  
Roberto Ligrone
Keyword(s):  
Root Nodules ◽  
Fungal Endophytes ◽  
Fungal Endophyte ◽  
Peninsular Malaysia ◽  
Epidermal Cells ◽  
Host Cells ◽  
Wall Material ◽  
Intercellular Spaces ◽  
Host Cytoplasm ◽  
Fungal Associations

The ventral epidermal cells of the photosynthetic, surface-living gametophytes of Lycopodium cernuum, collected from moist shaded banks in Peninsular Malaysia, contain an aseptate fungus. In some cells the hyphae are thick walled and form coils encapsulated by a thin layer of host wall material. In others the fungus is thin walled and shows limited differentiation into larger trunk hyphae and arbuscules. The adjacent host cytoplasm, separated from the fungus by a granular interfacial matrix, contains numerous chloroplasts, mitochondria, and microtubules. The hyphae contact the substratum via the ventral walls of the epidermal cells and the rhizoids are free from infection. In the protocorm and root nodules, aseptate hyphae initially colonize mucilage-filled schizogenous intercellular spaces. Subsequent invasion of the host cells is associated with the development of massive overgrowths of host wall material. The fungal associations in L. cernuum share a mixture of attributes otherwise found in different angiosperm mycorrhizae and in mycotrophic relationships in liverworts. Wall ingrowths are present in both the gametophyte and sporophyte cells in the placenta of L. cernuum. The very limited development of the placenta, compared with L. appressum, certain bryophytes and ferns, the diminutive size, and early senescence of the gametophytes of L. cernuum are all linked to the presence of the protocorm. This massive absorptive organ, homologous to a foot, in terms of its position in sporophyte ontogeny, but external to the parent gametophyte, derives its nutrition partly from photosynthesis and partly from its fungal endophyte. Key words: chloroplasts, Lycopodium, mycorrhiza, pteridophytes, root nodules, symbiosis, transfer cells.

ELECTRON MICROSCOPY OF THE BACTEROIDS AND ROOT NODULES OF LUPINUS LUTEUS

1965 ◽  
Vol 11 (4) ◽  
pp. 721-725 ◽  
Author(s):  
D. C. Jordan ◽  
I. Grinyer
Keyword(s):  
Plant Cell ◽  
De Novo ◽  
Root Nodules ◽  
Cell Plate ◽  
Lupinus Luteus ◽  
Bacterial Cells ◽  
Intercellular Spaces ◽  
Cortical Cells ◽  
Infection Threads ◽  
Spread Of Infection

No intracellular infection threads were observed in ultrathin sections of young root nodules of lupine, although nodule bacteria could be found in the intercellular spaces between the root cortical cells. Evidence suggests that in certain instances the plant cell walls can be disrupted locally, allowing the bacteria to pass into cytoplasm of the host cell. The spread of infection may be initiated in this manner and extended by division of infected cells. No plant-produced enclosing membranes were present around bacteria in the intercellular spaces but such structures developed after the bacteria had entered the plant cell. Although the origin of these membranes is debatable, in the present work it appeared that they were formed de novo, perhaps in a manner akin to the development of the cell plate during cell division. Most of the bacterial cells possessed a wide subwall space lying between the bacterial cell wall and plasma membrane. Discontinuities present in the latter membrane may account for the ribosome-like material found in the subwall space.

scholarly journals Morphogenesis of root nodules in white clover. II. The effect of mutation in genes nod IJ of the microsymbiont upon the nodule structure

2014 ◽  
Vol 67 (1) ◽  
pp. 5-22
Author(s):  
Barbara Łotocka ◽  
Joanna Kopcińska ◽  
Władysław Golinowski
Keyword(s):  
White Clover ◽  
Rhizobium Leguminosarum ◽  
Root Nodules ◽  
Single Cells ◽  
Wild Strain ◽  
Root Hairs ◽  
Nodule Development ◽  
Wild Type ◽  
Delayed Reaction ◽  
Infection Threads

Morphogenesis of ineffective root nodules initiated on the roots of white clover 'Astra' by the <em>Rhizobium leguminosarum</em> biovar. <em>trifolii</em> strains ANU261 (Tn5 insertion in nod 1 gene) and ANU262 (Tn5 insertion in nod J gene) was investigated. Following changes were observed, as compared to the wild-type nodulation: the exaggerated, not delayed reaction of root hairs; the delay in nodulation with the number of nodules the same as in plants inoculated with a wild strain; the formation and organization of the nodule primordium not changed in comparison with the wild-type nodules; infection threads abnormally branched and diffusing with bacteria deprived of light zone and enriched with storage material; infected cells of bacteroidal tissue abnormally strongly osmiophilic and only slightly vacuolated; symbiosomes with very narrowed peribacteroidal space, subject to premature degradation; abnormal accumulation of starch in the nodule tissues; nodule development blocked at the stage of laterally situated meristem and single nodule bundle; inhibition of divisions in the meristem and vacuolation of its cells; the appearance of single cells with colonies of saprophytic rhizobia embedded in the fibrillar matrix in the old, degraded regions of the bacteroidal tissue.

scholarly journals Lectin-Like Glycoprotein PsNLEC-1 Is Not Correctly Glycosylated and Targeted in Boron-Deficient Pea Nodules

2001 ◽  
Vol 14 (5) ◽  
pp. 663-670 ◽  
Author(s):  
Luis Bolaños ◽  
Arancha Cebrián ◽  
Miguel Redondo-Nieto ◽  
Rafael Rivilla ◽  
Ildefonso Bonilla
Keyword(s):  
Escherichia Coli ◽  
Gel Electrophoresis ◽  
Root Nodules ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Host Cells ◽  
Immunogold Localization ◽  
Electrophoretic Mobilities ◽  
Cytoplasmic Vesicles ◽  
Infected Cells

Symbiosome development was studied in pea root nodules from plants growing in the absence of boron (B). Rhizobia released into the host cells of nodules from B-deficient plants developed to abnormal endophytic forms with an altered electrophoretic lipopolysaccharide pattern. Immunostaining after sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electroblotting of nodule homogenates with antibodies that recognize glycoprotein components showed that two previously described lectin-like glycoproteins (PsNLEC-1A and PsNLEC-1B) did not harbor the carbohydrate epitope normally recognized by specific monoclonal antibodies. Material derived from B-deficient nodules, however, still contained three antigenic isoforms with similar electrophoretic mobilities to PsNLEC-1 isoforms A, B, and C. These could be detected following immunoblotting and immunostaining with a specific antiserum originating from the purified PsNLEC protein that had been heterologously expressed in Escherichia coli. Immunogold localization of PsNLEC-1 sugar epitopes in B-deficient nodules showed that they were associated mostly with cytoplasmic vesicles rather than normal localization in the symbiosome compartment of mature infected cells. These results suggest that a modification of the glycosyl-moieties of PsNLEC-1 and an alteration of vesicle targeting occur during the development of pea nodules in the absence of B, and that these changes are associated with the development of aberrant nonfunctional symbiosomes.

Rhizobium infection threads in root hairs of Glycine max (L.) Merr., Glycine soja Sieb. & Zucc, and Vigna unguiculata (L.) Walp.

1983 ◽  
Vol 29 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Steven G. Pueppke
Keyword(s):  
Glycine Max ◽  
Vigna Unguiculata ◽  
Glycine Soja ◽  
Primary Root ◽  
Wild Soybean ◽  
Root Hairs ◽  
Infected Root ◽  
Infection Threads ◽  
Basal Portion ◽  
Rhizobium Sp

Eight lines of soybean (Glycine max), four of wild soybean (Glycine soja), and one cowpea (Vigna unguiculata) cultivar were inoculated with 18 Rhizobium strains. After 4 days, root hairs were examined for infection threads. Threads were produced by all hosts but exclusively in nodulating combinations. Only Rhizobium sp. strains 3G4b9a and 3G4b19 were inconsistent; they nodulated soybean and G. soja in some experiments, but rarely formed infection threads. Soybean and G. soja were indistinguishable in their interactions with rhizobia, as were lele soybean lines (genetically lack soybean lectin), Hardee soybean (contains the noduation-influencing genes Rj2 and Rj3), and several other soybean cultivars. Threads formed in cowpea with all of the R. japonicum strains and most Rhizobium sp. but not with R. lupini. Infection of all three host species occurred in portions of the primary root containing immature or no root hairs at the time of inoculation; proximal tissues having elongated root hairs lacked infection threads. Infected root hairs were short and commonly shaped like question marks. Threads usually branched and sometimes intertwined prior to elongation into the basal portion of root hairs.

scholarly journals Identification of a Family of Extensin-Like Glycoproteins in the Lumen of Rhizobium-Induced Infection Threads in Pea Root Nodules

2002 ◽  
Vol 15 (4) ◽  
pp. 350-359 ◽  
Author(s):  
Elizabeth A. Rathbun ◽  
Michael J. Naldrett ◽  
Nicholas J. Brewin
Keyword(s):  
Posttranscriptional Regulation ◽  
Rhizobium Leguminosarum ◽  
Root Nodules ◽  
Regulation Of Gene Expression ◽  
Pcr Primers ◽  
Amino Acid Sequences ◽  
Sequence Conservation ◽  
Host Cells ◽  
Cdna Clones ◽  
Infection Threads

Rhizobium leguminosarum bv. viciae normally gains access to pea host cells through tubular cell wall ingrowths termed infection threads. Matrix glycoprotein (MGP), a major component of the infection thread lumen, is also secreted from the tips of uninoculated roots and can be released into solution under reducing conditions. Monoclonal antibody MAC265, which recognizes MGP through a carbohydrate epitope, was used for immunoaffinity purification of the glycoprotein from pea roots. Following treatment with chymotrypsin, a peptide fragment was obtained and subjected to N-terminal sequencing. Using PCR primers based on this sequence, cDNA clones were isolated with RNA from inoculated roots and nodules. DNA sequencing of 30 of these clones revealed a family of closely related and repetitive polypeptides with (hydroxy)proline-rich motifs. The cDNA sequences showed over 70% identity with the deduced amino acid sequences of plant extensins, particularly with VfNDS-E from Vicia faba and MtN12 from Medicago truncatula, both of which are strongly upregulated in legume root nodules. Root nodule extensins from pea were of variable length but showed strong sequence conservation of the N-terminus, of the C-terminus, and of a central domain comprising 33 amino acids that were sometimes reiterated. The distribution of tyrosine residues suggested the possible importance of intramolecular and intermolecular cross-linking. There was strong sequence conservation with MtN12 in the 3′-untranslated region, suggesting a possible involvement in posttranscriptional regulation of gene expression.

Infection process and sloughing off of rhizobial outer membrane in effective nodules of lima bean

1982 ◽  
Vol 28 (7) ◽  
pp. 890-896 ◽  
Author(s):  
Arya K. Bal ◽  
Peter P. Wong
Keyword(s):  
Cell Wall ◽  
Outer Membrane ◽  
Root Hairs ◽  
Lima Bean ◽  
Infection Process ◽  
Epidermal Cells ◽  
Infection Threads ◽  
Lima Beans ◽  
Membrane Cell ◽  
Rhizobium Sp

In addition to infection via root hairs, infection threads originating in epidermal cells after colonization of epidermis have been clearly demonstrated in lima beans infected with Rhizobium sp. 127E15, and this double mode of infection possibly accounts for profuse nodulation of the roots. Sloughing off of the outer membrane (cell wall) was detected after release of rhizobia during bacteroid differentiation in effective nodules.

Comparison of the genomic arrangement and the relative transcription of the nitrogenase genes in Rhizobium meliloti during symbiotic development in alfalfa root nodules

1982 ◽  
Vol 28 (12) ◽  
pp. 1330-1339 ◽  
Author(s):  
Alan S. Paau ◽  
Winston J. Brill
Keyword(s):  
Rhizobium Meliloti ◽  
Protein Pattern ◽  
Root Nodules ◽  
Symbiotic Association ◽  
Free Living ◽  
Genomic Arrangement ◽  
Infection Threads ◽  
Nitrogenase Genes ◽  
Specific Amplification ◽  
Alfalfa Root

In the course of the symbiotic development of free-living rhizobia to mature bacteroids in alfalfa nodules, mRNA transcripts of the nitrogenase structural genes are first detected when the rhizobia are inside the infection threads. These transcripts are most abundant in the mature bacteroids of young (6 to 8 weeks) root nodules and are present in a much lower level in bacteroids from senescent root nodules (13 weeks). Translation of these and related rhizobial genes essential for the symbiotic association apparently occurs very early in the symbiosis because the protein pattern of the "infection thread rhizobia" is very similar to that of the mature bacteroids and is different from that of the cultured vegetative rhizobia. Although bacteroids have a higher DNA content than the vegetative bacteria and are very different in the nucleoid organization, no specific amplification or rearrangement of the nitrogenase genes is detected in bacteroids.

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