Nodule morphogenesis: the early infection of Alfalfa (Medicago sativa) root hairs by Rhizobium meliloti

1989 ◽  
Vol 67 (10) ◽  
pp. 3108-3122 ◽  
Author(s):  
Susan M. Wood ◽  
William Newcomb
Keyword(s):  
Medicago Sativa ◽  
Root Hair ◽  
Rhizobium Meliloti ◽  
Root Hairs ◽  
Growth Period ◽  
Active Phase ◽  
Infection Threads ◽  
Thread Formation ◽  
Time Of Infection ◽  
Meliloti Strain

The growth and development of alfalfa (Medicago sativa) cv. Saranac root hairs and their infection by Rhizobium meliloti strain 102F51 was studied with Smith's interference contrast optics. Uninoculated root hairs grew and matured over a 10-h growth period. The nucleus migrated from a position opposite that of root-hair protrusion at initiation to the base of the root-hair protrusion, then into the growing root hair during the most active phase. When growth was nearly complete, the nucleus assumed a position near the base of the vacuolate root hair. If root hairs were inoculated during the first 2 h of growth after initiation, either "Shepherd's crooks" or root hairs deformed into a tight curl as the tip developed. Some of these Shepherd's rooks later demonstrated typical infection-thread formation. Root hairs that were inoculated between 4 and 6 h after root-hair initiation demonstrated branched growth, with the branch forming opposite the position of the nucleus at the time of infection. Infection threads occasionally formed in either the side branches or tip branches. Root hairs that were older than 6 h at the time of inoculation formed a variety of growth deformations, including ballooning, and elongate, spatulate, spiralling, or intertwined growth. Infections in this population of root hairs were rare.

Physiological and morphological aspects of interactions between Rhizobium meliloti and alfalfa (Medicago sativa) in association with Azospirillum brasilense

1993 ◽  
Vol 39 (6) ◽  
pp. 610-615 ◽  
Author(s):  
R. Itzigsohn ◽  
Y. Kapulnik ◽  
Y. Okon ◽  
A. Dovrat
Keyword(s):  
Medicago Sativa ◽  
Rhizobium Meliloti ◽  
Combined Treatment ◽  
Root Hairs ◽  
Background Level ◽  
Root Surface ◽  
Root Surface Area ◽  
Main Root ◽  
Nodule Number ◽  
Infection Threads

In a 50-L pot experiment with Medicago sativa grown under nonsterile conditions, a combined treatment of Azospirillum and Rhizobium was measured against soil inoculated with Rhizobium or Azospirillum alone or a control with a low background level of autochthonous rhizobia. The combined treatment significantly increased the shoot length and weight at 6 weeks and the regrowth shoot weight at 14 weeks when compared with the treatment with Rhizobium alone. In 1.5-L pots in which gnotobiotic conditions were maintained, the combined treatment led to more nodules on the main root at intermediate Rhizobium concentrations, and a greater root surface area at intermediate and high Rhizobium concentrations after 2 weeks but not after 4 weeks. In pouch-grown seedlings, plants were inoculated with either Rhizobium alone or in combination with Azospirillum or applied together with a flavonoid, luteolin (a nodulation gene inducer), or with a cytokinin, benzyl adenine. Luteolin had similar effects to those of Azospirillum in increasing the main root nodule number and the total nodule number. With Fahraeus slides, a significant increase was observed in the number of root hairs and the root diameter in the presence of Azospirillum as compared with the control and Rhizobium alone. There was no increase in the total number of infection threads; however, the combined treatment caused a significant decrease in the percentage of infected root hairs.Key words: Rhizobium, Azospirillum, Medicago, flavonoid, inoculation.

scholarly journals Host Specificity In The Root Hair "Curling Factor" of Rhizobium Spp.

1969 ◽  
Vol 22 (2) ◽  
pp. 413 ◽  
Author(s):  
Phaik Y Yao ◽  
JM Vincent
Keyword(s):  
Medicago Sativa ◽  
Host Specificity ◽  
Root Hair ◽  
Root Zone ◽  
Root Hairs ◽  
Degree Of Deformation ◽  
Medicago Sativa L ◽  
Rhizobium Spp ◽  
Hair Curling ◽  
Root Hair Curling

Thirty-eight cultures of rhizobia and 10 non-rhizobia growing in the root zone of clover (Trifolium glomeratum L.), 5 rhizobia and 3 non-rhizobia in that of lucerne (Medicago sativa L.), and 8 rhizobia in that ofSiratro (Phaseolus atropurpureus DO.) revealed a specific relationship between bacteria and host that determined the kind and degree of deformation of the root hairs.

scholarly journals H2O2 Is Required for Optimal Establishment of the Medicago sativa/Sinorhizobium meliloti Symbiosis

2007 ◽  
Vol 189 (23) ◽  
pp. 8741-8745 ◽  
Author(s):  
Alexandre Jamet ◽  
Karine Mandon ◽  
Alain Puppo ◽  
Didier Hérouart
Keyword(s):  
Medicago Sativa ◽  
Plant Cell ◽  
Sinorhizobium Meliloti ◽  
Root Hairs ◽  
Symbiotic Interaction ◽  
Infection Threads ◽  
Cell Layers

ABSTRACT The symbiotic interaction between Medicago sativa and Sinorhizobium meliloti RmkatB ++ overexpressing the housekeeping catalase katB is delayed, and this delay is combined with an enlargement of infection threads. This result provides evidence that H2O2 is required for optimal progression of infection threads through the root hairs and plant cell layers.

Infection thread formation as a basis of nodulation specificity in Rhizobium – strawberry clover associations

1969 ◽  
Vol 15 (10) ◽  
pp. 1133-1136 ◽  
Author(s):  
Diana Li ◽  
D. H. Hubbell
Keyword(s):  
Characteristic Root ◽  
Root Hairs ◽  
Infection Thread ◽  
Root Hair Deformation ◽  
Infection Threads ◽  
Specific Substance ◽  
Thread Formation ◽  
Nodulation Specificity ◽  
Infection Thread Formation

The basis for determination of nodulating specificity in Rhizobium–clover associations was investigated. Thirteen strains of rhizobia from eight different cross-inoculation groups were used to inoculate aseptically grown strawberry clover seedlings in slide culture. Microscopic observation revealed that each strain produced characteristic root hair deformation but infection threads and nodules were observed only in the homologous combination. It is concluded that, in rhizobia–clover combinations which nodulate via infection threads, specificity is determined at or before infection thread initiation. Observations of other workers that rhizobia produce a strain-specific substance affecting growth and morphology of legume root hairs were confirmed by results of this study.

Localization of oleosomes in the root nodules of alfalfa (Medicago sativa)

1998 ◽  
Vol 76 (8) ◽  
pp. 1418-1423 ◽  
Author(s):  
A Darryl Martin ◽  
Arya K Bal ◽  
David B McKenzie
Keyword(s):  
Medicago Sativa ◽  
Vascular Tissue ◽  
Rhizobium Meliloti ◽  
Root Nodules ◽  
Hexane Extraction ◽  
En Bloc ◽  
Cortical Cells ◽  
Storage Organs ◽  
Vascular Parenchyma ◽  
Meliloti Strain

Histological studies of rhizobia-induced nodules and spontaneous pseudonodules of alfalfa were undertaken to reveal the distribution pattern of oleosomes. Alfalfa (Medicago sativa L. cv. 'Algonquin') seedlings were inoculated with Rhizobium meliloti (strain Balsac), and grown in controlled conditions. Seedlings were also grown aseptically to obtain spontaneous pseudonodules. Nodule slices were fixed in a paraformaldehyde-glutaraldehyde mixture and processed for embedding in Spurr's medium after OsO4 treatment and en bloc staining, with p-phenylenediamine (pPD) in 70% ethanol, for oleosomes. As a control, hexane extraction of lipids was employed. In pseudonodules, oleosomes were present in the vascular parenchyma, the meristem region and in the five to seven layers of cortical cells adjacent to the vascular tissue. The allocation of energy stored as triacylglycerides, in the form of oleosomes, and starch indicates that pseudonodules are a sink for carbon, possibly functioning as storage organs. In mature nodules, oleosomes were distinguished clearly in nodule parenchyma but were absent in infected cells. Young nodules were devoid of oleosomes. The prevalence of oleosomes in the mature nodules may indicate that the triacylglycerides are stored for overwintering, as alfalfa nodules are known to be perennial. The oleosomes in root nodules of alfalfa do not appear to be directly associated with nitrogen fixation per se.Key words: oleosomes, root nodules, Medicago sativa, Rhizobium, pseudonodules.

Early events in the infection of soybean by Rhizobium japonicum. Time course and cytology of the initial infection process

1982 ◽  
Vol 60 (2) ◽  
pp. 152-161 ◽  
Author(s):  
B. Gillian Turgeon ◽  
Wolfgang D. Bauer
Keyword(s):  
Root Hair ◽  
Time Course ◽  
Cortical Cell ◽  
Root Hairs ◽  
Infection Process ◽  
Infection Thread ◽  
Rhizobium Japonicum ◽  
Outer Cortex ◽  
Light Microscope Level ◽  
Infection Threads

The time course of early infection events in Glycine max following inoculation with Rhizobium japonicum is described. Bacteria became attached to epidermal cells and root hairs within minutes of inoculation. Marked root hair curling occurred within 12 h. Infection thread formation was visible at the light microscope level of resolution about 24 h after inoculation. Infections were observed in short, tightly curled root hairs. These root hairs had not yet emerged at the time of inoculation. Infection threads appeared to originate in pockets formed by contact of the cell wall of the curled root hair with itself. Infection threads in the hairs were multiple and (or) branched. By 48 h, the infection thread(s) had progressed to the base of the root hair but had not yet penetrated into the cortex. Increases in cortical cell cytoplasm and in mitotic division occurred in advance of the penetrating infection thread. A nodule meristem developed in the outer cortex next to the infected root hair by 4 days and was accompanied by cell division across the cortex.

The nodDABC Genes of Rhizobium leguminosarum biovar trifolii Confer Root-Hair Curling Ability to a Diverse Range of Soil Bacteria and the Ability to Induce Novel Root Swellings on Beans

1994 ◽  
Vol 21 (3) ◽  
pp. 311 ◽  
Author(s):  
J Plazinski ◽  
RW Ridge ◽  
IA Mckay ◽  
MA Djordjevic
Keyword(s):  
Root Hair ◽  
Soil Bacteria ◽  
Rhizobium Leguminosarum ◽  
Plant Root ◽  
Root Hairs ◽  
Infection Threads ◽  
Wide Range ◽  
Hair Curling ◽  
Root Hair Curling ◽  
Rhizobium Leguminosarum Biovar Trifolii

Cloned DNA fragments coding for the nodDABC genes of Rhizobium leguminosarum biovar trifolii strain ANU843 were introduced into Rhizobium strains possessing Sym plasmid deletions. These strains were able to: (a) synthesise four butanol-soluble Nod metabolites; (b) affect the normal growth pattern of plant root hairs of a wide range of host and non-host legumes; and (c) induce many root outgrowths on Phaseolus plants. The four Nod metabolites produced by these strains were labelled by supplying cultures with 14C-acetate in the presence of a flavonoid inducer of nod gene expression. In contrast, more than ten Nod metabolites were synthesised by wild-type strains or constructed strains containing the full complement of R. leguminosarum biovar. trifolii nodulation and host specific nodulation genes. Strain ANU845 containing nodDABC did not induce infection threads or nodule initiation sites but distorted and curled cells in plant root hairs. However strain ANU845 induced root outgrowths on beans (Phaseolus vulgaris) that appeared to result from a proliferation of the epidermal tissue. Transfer of plasmids bearing nodDABC to various Gram-negative bacteria, Agrobacterium tumefaciens, Pseudomonas aeruginosa, Lignobacter sp., Azospirillum brasilense and Escherichia coli, and different non-nodulating mutant rhizobia conferred on these strains the ability to cause root-hair curling and distortions. Several strains induced root-hair curling on clover and a range of other non-host legumes. We suggest that the expression of nodDABC in a range of soil bacteria may extend or alter the effects of these soil bacteria on the roots of host plants.

scholarly journals Function of Succinoglycan Polysaccharide inSinorhizobium melilotiHost Plant Invasion Depends on Succinylation, Not Molecular Weight

mBio ◽  
2016 ◽  
Vol 7 (3) ◽  
Author(s):  
Hajeewaka C. Mendis ◽  
Thelma F. Madzima ◽  
Clothilde Queiroux ◽  
Kathryn M. Jones
Keyword(s):  
Molecular Weight ◽  
Host Plant ◽  
Sinorhizobium Meliloti ◽  
Plant Root ◽  
Root Hairs ◽  
Critical Feature ◽  
Acidic Polysaccharide ◽  
Infection Threads ◽  
Thread Formation ◽  
Infection Thread Formation

ABSTRACTThe acidic polysaccharide succinoglycan produced by the rhizobial symbiontSinorhizobium meliloti1021 is required for this bacterium to invade the host plantMedicago truncatulaand establish a nitrogen-fixing symbiosis.S. melilotimutants that cannot make succinoglycan cannot initiate invasion structures called infection threads in plant root hairs.S. melilotiexoH mutants that cannot succinylate succinoglycan are also unable to form infection threads, despite the fact that they make large quantities of succinoglycan. Succinoglycan produced byexoHmutants is refractory to cleavage by the glycanases encoded byexoKandexsH, and thus succinoglycan produced byexoHmutants is made only in the high-molecular-weight (HMW) form. One interpretation of the symbiotic defect ofexoHmutants is that the low-molecular-weight (LMW) form of succinoglycan is required for infection thread formation. However, our data demonstrate that production of the HMW form of succinoglycan byS. meliloti1021 is sufficient for invasion of the hostM. truncatulaand that the LMW form is not required. Here, we show thatS. melilotistrains deficient in theexoK- andexsH-encoded glycanases invadeM. truncatulaand form a productive symbiosis, although they do this with somewhat less efficiency than the wild type. We have also characterized the polysaccharides produced by these double glycanase mutants and determined that they consist of only HMW succinoglycan and no detectable LMW succinoglycan. This demonstrates that LMW succinoglycan is not required for host invasion. These results suggest succinoglycan function is not dependent upon the presence of a small, readily diffusible form.IMPORTANCESinorhizobium melilotiis a bacterium that forms a beneficial symbiosis with legume host plants.S. melilotiand other rhizobia convert atmospheric nitrogen to ammonia, a nutrient source for the host plant. To establish the symbiosis, rhizobia must invade plant roots, supplying the proper signals to prevent a plant immune response during invasion. A polysaccharide, succinoglycan, produced byS. melilotiis required for successful invasion. Here, we show that the critical feature of succinoglycan that allows infection to proceed is the attachment of a “succinyl” chemical group and that the chain length of succinoglycan is much less important for its function. We also show that none of the short-chain versions of succinoglycan is produced in the absence of two chain-cleaving enzymes.

scholarly journals Role of Exopolysaccharides of Rhizobium leguminosarum bv. viciae as Host Plant-Specific Molecules Required for Infection Thread Formation During Nodulation of Vicia sativa

1998 ◽  
Vol 11 (12) ◽  
pp. 1233-1241 ◽  
Author(s):  
Wilbert A. T. van Workum ◽  
Sophie van Slageren ◽  
Anton A. N. van Brussel ◽  
Jan W. Kijne
Keyword(s):  
Root Hair ◽  
Rhizobium Leguminosarum ◽  
Root Penetration ◽  
Vicia Sativa ◽  
Infection Threads ◽  
Efficient Induction ◽  
Thread Formation ◽  
Hair Curling ◽  
Root Hair Curling

Mutants of Rhizobium leguminosarum bv. viciae bacteria that are affected in the biosynthesis of exopolysaccharides (EPS) are unable to effectively nodulate their host plants. By studying defined mutants, we show that R. legumi-nosarum bv. viciae strains require EPS for formation of infection threads in Vicia sativa (vetch) as well as for efficient induction of tight root hair curling. Results of coinoculation experiments with the EPS-deficient pssD111 mutant of R. leguminosarum bv. viciae in combination with heterologous EPS-producing strains indicated that vetch has certain structural requirements for rhizobial EPS to function in symbiosis. We hypothesize that EPS accelerates root hair curling and infection to such an extent that rhizobial root penetration precedes a plant defense response.

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