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 Transcriptomic analysis with the progress of symbiosis in ‘crack-entry’ legume Arachis hypogaea highlights its contrast with ‘infection thread’ adapted legumes

2018 ◽  
Author(s):  
Kanchan Karmakar ◽  
Anindya Kundu ◽  
Ahsan Z Rizvi ◽  
Emeric Dubois ◽  
Dany Severac ◽  
...  
Keyword(s):  
Arachis Hypogaea ◽  
Root Nodule ◽  
Infection Thread ◽  
Symbiotic Genes ◽  
Cortical Cells ◽  
Transcriptional Dynamics ◽  
Infection Threads ◽  
Spread Of Infection ◽  
Molecular Framework ◽  
Nodule Symbiosis

ABSTRACTIn root-nodule symbiosis, rhizobial invasion and nodule organogenesis is host controlled. In most legumes, rhizobia enter through infection-threads and nodule primordium in the cortex is induced from a distance. But in dalbergoid legumes like Arachis hypogaea, rhizobia directly invade cortical cells through epidermal cracks to generate the primordia. Herein we report the transcriptional dynamics with the progress of symbiosis in A. hypogaea at 1dpi: invasion; 4dpi: nodule primordia; 8dpi: spread of infection in nodule-like structure; 12dpi: immature nodules containing rod-shaped rhizobia; and 21dpi: mature nodules with spherical symbiosomes. Expression of putative orthologue of symbiotic genes in ‘crack-entry’ legume A. hypogaea was compared with infection thread adapted model legumes. The contrasting features were (i) higher expression of receptors like LYR3, EPR3 as compared to canonical NFRs (ii) late induction of transcription factors like NIN, NSP2 and constitutive high expression of ERF1, EIN2, bHLH476 and (iii) induction of divergent pathogenesis responsive PR-1 genes. Additionally, symbiotic orthologues of SymCRK, FLOT4, ROP6, RR9, NOOT and SEN1 were not detectable and microsynteny analysis indicated the absence of RPG and DNF2 homologues in diploid parental genomes of A. hypogaea. The implications are discussed and a molecular framework that guide ‘crack-entry’ symbiosis in A. hypogaea is proposed.

scholarly journals Auxin: at the root of nodule development?

2008 ◽  
Vol 35 (8) ◽  
pp. 651 ◽  
Author(s):  
Ulrike Mathesius
Keyword(s):  
Lateral Root ◽  
De Novo ◽  
Root Nodules ◽  
Lateral Roots ◽  
Nodule Development ◽  
Nodule Formation ◽  
Cortical Cells ◽  
Lateral Root Development ◽  
Organ Differentiation ◽  
Development And Differentiation

Root nodules are formed as a result of an orchestrated exchange of chemical signals between symbiotic nitrogen fixing bacteria and certain plants. In plants that form nodules in symbiosis with actinorhizal bacteria, nodules are derived from lateral roots. In most legumes, nodules are formed de novo from pericycle and cortical cells that are re-stimulated for division and differentiation by rhizobia. The ability of plants to nodulate has only evolved recently and it has, therefore, been suggested that nodule development is likely to have co-opted existing mechanisms for development and differentiation from lateral root formation. Auxin is an important regulator of cell division and differentiation, and changes in auxin accumulation and transport are essential for lateral root development. There is growing evidence that rhizobia alter the root auxin balance as a prerequisite for nodule formation, and that nodule numbers are regulated by shoot-to-root auxin transport. Whereas auxin requirements appear to be similar for lateral root and nodule primordium activation and organ differentiation, the major difference between the two developmental programs lies in the specification of founder cells. It is suggested that differing ratios of auxin and cytokinin are likely to specify the precursors of the different root organs.

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.

Cytoplasmic bridge formation in the nodule apex of actinorhizal root nodules

1999 ◽  
Vol 77 (9) ◽  
pp. 1351-1357 ◽  
Author(s):  
R Howard Berg
Keyword(s):  
Structural Changes ◽  
Root Nodules ◽  
Parenchyma Cell ◽  
Infection Process ◽  
Infection Thread ◽  
Cytoplasmic Bridge ◽  
Cortical Cells ◽  
Infection Threads ◽  
Related Plant ◽  
Cytoplasmic Bridges

High-pressure frozen - freeze-substituted actinorhizal root nodules of several distantly related plant genera were used to document the sequence of structural changes in cortical cells of the nodule apex that happened prior to their infection. The sequence of mobilization of the plant cell cytoplasm requisite to infection by Frankia was (i) penetration of the parenchyma cell vacuole by cytoplasmic strands, which contained microtubules; (ii) movement of the nucleus and other organelles (Golgi stacks, endoplasmic reticulum, mitochondria), involved later in growth of the infection thread, to the cell center on these strands; (iii) thickening of some of these strands generally located at midpoints of the wall, forming cytoplasmic bridges (preinfection threads); and (iv) infection of the cell by initiation of infection threads (containing Frankia) within the cytoplasmic bridges. The infection thread was caged in microtubules that were oriented along its axis, suggesting the cytoskeleton had a major role in the infection process, perhaps guiding the growth of the infection thread across the cell. The coalignment of cytoplasmic bridges, along several cells, towards the advancing microsymbiont suggested Frankia secretes a diffusible signal eliciting this host response.Key words: actinorhiza, cryofixation, development, infection, microtubules, symbiosis.

scholarly journals The Early Nodulin Gene MtN6 Is a Novel Marker for Events Preceding Infection of Medicago truncatula Roots by Sinorhizobium meliloti

1999 ◽  
Vol 12 (6) ◽  
pp. 544-555 ◽  
Author(s):  
R. Mathis ◽  
C. Grosjean ◽  
F. de Billy ◽  
T. Huguet ◽  
P. Gamas
Keyword(s):  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Root Nodules ◽  
Cdna Clones ◽  
Specific Marker ◽  
Nod Factors ◽  
Cortical Cells ◽  
Infection Threads ◽  
Early Nodulin ◽  
Cell Layers

MtN6 belongs to a series of cDNA clones representing Medicago truncatula genes transcriptionally activated during nodulation by Sinorhizobium meliloti (P. Gamas, F. de Carvalho Niebel, N. Lescure, and J. V. Cullimore, Mol. Plant-Microbe Interact. 9:233–242, 1996). We show here by in situ hybridization that MtN6 transcripts specifically accumulate first at very localized regions in the outer root cell layers, corresponding to outer cortical cells containing preinfection threads. At later stages, MtN6 expression is observed ahead of growing infection threads, including in the infection zone of mature root nodules. Interestingly, regulation of MtN6 is clearly distinct from that of other early nodulins expressed in the same region of the nodule, in terms of response to bacterial symbiotic mutants and to purified Nod factors. We thus suggest that MtN6 represents the first specific marker of a pathway involved in preparation to infection, which is at least partly controlled by Nod factors. Finally, we discuss the intriguing sequence homology shown by MtN6 to a protein from Emericella (Aspergillus) nidulans, FluG, that plays a key role in controlling the organogenesis of conidiophores (B. N. Lee and T. H. Adams, Genes Dev. 8:641–651, 1994).

scholarly journals Transcriptomic Analysis With the Progress of Symbiosis in ‘Crack-Entry’ Legume Arachis hypogaea Highlights Its Contrast With ‘Infection Thread’ Adapted Legumes

2019 ◽  
Vol 32 (3) ◽  
pp. 271-285 ◽  
Author(s):  
Kanchan Karmakar ◽  
Anindya Kundu ◽  
Ahsan Z Rizvi ◽  
Emeric Dubois ◽  
Dany Severac ◽  
...  
Keyword(s):  
Arachis Hypogaea ◽  
Root Nodule ◽  
Infection Thread ◽  
Cortical Cells ◽  
Nod Factor ◽  
Transcriptional Dynamics ◽  
Infection Threads ◽  
Spread Of Infection ◽  
Molecular Framework ◽  
Nodule Symbiosis

In root-nodule symbiosis, rhizobial invasion and nodule organogenesis is host controlled. In most legumes, rhizobia enter through infection threads and nodule primordium in the cortex is induced from a distance. But in dalbergoid legumes like Arachis hypogaea, rhizobia directly invade cortical cells through epidermal cracks to generate the primordia. Herein, we report the transcriptional dynamics with the progress of symbiosis in A. hypogaea at 1 day postinfection (dpi) (invasion), 4 dpi (nodule primordia), 8 dpi (spread of infection in nodule-like structure), 12 dpi (immature nodules containing rod-shaped rhizobia), and 21 dpi (mature nodules with spherical symbiosomes). Expression of putative ortholog of symbiotic genes in ‘crack entry’ legume A. hypogaea was compared with infection thread–adapted model legumes. The contrasting features were i) higher expression of receptors like LYR3 and EPR3 as compared with canonical Nod factor receptors, ii) late induction of transcription factors like NIN and NSP2 and constitutive high expression of ERF1, EIN2, bHLH476, and iii) induction of divergent pathogenesis-responsive PR-1 genes. Additionally, symbiotic orthologs of SymCRK, ROP6, RR9, SEN1, and DNF2 were not detectable and microsynteny analysis indicated the absence of a RPG homolog in diploid parental genomes of A. hypogaea. The implications are discussed and a molecular framework that guides crack-entry symbiosis in A. hypogaea is proposed.

A reinvestigation of the origin of the peribacteroid membrane in root nodules of Vicia faba

1981 ◽  
Vol 59 (9) ◽  
pp. 1547-1552 ◽  
Author(s):  
William Newcomb ◽  
Susan Creighton ◽  
Lenore Latta
Keyword(s):  
Plasma Membrane ◽  
Vicia Faba ◽  
De Novo ◽  
Root Nodules ◽  
Electron Microscopic ◽  
Peribacteroid Membrane ◽  
Transmission Electron Microscopic Study ◽  
Transmission Electron ◽  
Infection Threads ◽  
Transmission Electron Microscopic

A transmission electron microscopic study of nodules of Vicia faba has demonstrated that rhizobia are released from the infection threads by an endocytotic process. The rhizobia escape from unwalled regions of the infection thread or unwalled droplets of thread matrix and upon escape are surrounded by a peribacteroid membrane which is derived from the plasma membrane bounding the unwalled regions of thread matrix. Thus, the release of bacteria in V. faba nodules is essentially identical to that reported in other leguminous nodules and the peribacteroid membrane does not arise de novo as previously reported by other workers.

Host–endophyte interactions in effective and ineffective nodules induced by the endophyte of Myrica gale

1983 ◽  
Vol 61 (11) ◽  
pp. 2898-2909 ◽  
Author(s):  
Kathryn A. VandenBosch ◽  
John G. Torrey
Keyword(s):  
Nitrogenase Activity ◽  
Root Nodules ◽  
Seedling Development ◽  
Nodule Development ◽  
Nodule Formation ◽  
Cortical Tissue ◽  
Intercellular Spaces ◽  
Cortical Cells ◽  
Myrica Gale ◽  
Infected Cells

Suspensions of crushed root nodules of Myrica gale containing the actinomycete Frankia induced nodule formation on roots of seedlings of M. gale and Comptonia peregrina grown in nutrient water culture. Nodules formed on M. gale were normal in structure and exhibited nitrogenase activity (measured as acetylene reduction) and provided the necessary nitrogen for seedling development. These effective nodules showed typical external and internal structure with the endophyte developing both vesicles and sporangia within cortical cells of the host tissue. Small nodules formed on C. peregrina representing the primary nodule stage. They lacked nitrogenase activity and were termed ineffective. Vesicles failed to develop within these ineffective nodules. However, sporangia were formed in infected cells and within intercellular spaces of the nodule cortical tissue. In addition, prominent amyloplasts occurred in infected cells of the ineffective nodules, a feature lacking in effective nodules. Exogenously supplied combined nitrogen increased seedling growth but did not improve nodule development or endophyte morphogenesis in the ineffective nodules.

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.

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