Defective Infection and Nodulation of Clovers by Exopolysaccharide Mutants of Rhizobium leguminosarum bv. trifolii

1996 ◽  
Vol 23 (3) ◽  
pp. 285 ◽  
Author(s):  
BG Rolfe ◽  
RW Carlson ◽  
RW Ridge ◽  
FB Dazzo ◽  
PF Mateos ◽  
...  
Keyword(s):  
Root Hair ◽  
Rhizobium Leguminosarum ◽  
Plant Cells ◽  
Growth Conditions ◽  
Infection Threads ◽  
Clover Root ◽  
Thread Formation ◽  
Symbiotic Properties ◽  
Hair Curling ◽  
Root Hair Curling

The biological and symbiotic properties of two types of exopolysaccharide deficient (Exo- phenotype) mutants of Rhizobium leguminosarum were investigated. One mutant, a pss1 derivative (ANU437) of R. l. bv. trifolii, produces very low levels of acidic exopolysaccharide (EPS) and of the acidic oligosaccharide (AOS) repeating unit lacking its O-acetyl substituent. The second strain, originally a R. I. bv. viciae derivative, but containing a clover pSym plasmid (Exo-1 mutant ANU54(pBRIAN)), did not produce any EPS polymer or detectable oligosaccharide repeating unit. The Exo- mutants formed no capsules and their growth in laboratory media was comparable to their parent strains but was inhibited by the addition of the phytoalexins medicarpin and kievitone, but not by the phytoalexin pisatin. Both Exo- mutants were slow to induce clover root hair curling (Hac+), and formed growing infection threads (Inf-) only on white clovers. However, the extent of these early symbiotic defects depended on the plant growth conditions used. Both mutants induced small non-nitrogen-fixing (Fix-) nodules on white and subterranean clovers. Within the white clover nodules induced by mutant ANU437, bacteria were released into plant cells. On white clovers at elevated light and temperature conditions, the Exo-1 mutant ANU54(pBRIAN) usually failed to initiate infection threads and thus formed empty nodules which do not contain any bacteria. In addition, this mutant formed only empty nodules without infection threads on subterranean clovers under all growth conditions tested. The outermost layers of plant cells in these empty nodules had thickened cell walls and deposited materials. These experiments show that EPS synthesis is essential for the induction of rapid root hair curling, proper infection thread formation and the ability to sustain the growth of induced nodules on various clovers.

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.

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 The HCL gene of Medicago truncatula controls Rhizobium-induced root hair curling

Development ◽  
2001 ◽  
Vol 128 (9) ◽  
pp. 1507-1518 ◽  
Author(s):  
R. Catoira ◽  
A.C. Timmers ◽  
F. Maillet ◽  
C. Galera ◽  
R.V. Penmetsa ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Root Hair ◽  
Cortical Cell ◽  
Wild Type ◽  
Cortical Cells ◽  
Model Legume ◽  
Infection Threads ◽  
Microtubular Cytoskeleton ◽  
Hair Curling ◽  
Root Hair Curling

The symbiotic infection of the model legume Medicago truncatula by Sinorhizobium meliloti involves marked root hair curling, a stage where entrapment of the microsymbiont occurs in a chamber from which infection thread formation is initiated within the root hair. We have genetically dissected these early symbiotic interactions using both plant and rhizobial mutants and have identified a M. truncatula gene, HCL, which controls root hair curling. S. meliloti Nod factors, which are required for the infection process, induced wild-type epidermal nodulin gene expression and root hair deformation in hcl mutants, while Nod factor induction of cortical cell division foci was reduced compared to wild-type plants. Studies of the position of nuclei and of the microtubule cytoskeleton network of hcl mutants revealed that root hair, as well as cortical cells, were activated in response to S. meliloti. However, the asymmetric microtubule network that is typical of curled root hairs, did not form in the mutants, and activated cortical cells did not become polarised and did not exhibit the microtubular cytoplasmic bridges characteristic of the pre-infection threads induced by rhizobia in M. truncatula. These data suggest that hcl mutations alter the formation of signalling centres that normally provide positional information for the reorganisation of the microtubular cytoskeleton in epidermal and cortical cells.

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.

Rhizobium nodulation genes involved in root hair curling (Hac) are functionally conserved

1985 ◽  
Vol 4 (2-3) ◽  
pp. 147-160 ◽  
Author(s):  
M. A. Djordjevic ◽  
P. R. Schofield ◽  
R. W. Ridge ◽  
N. A. Morrison ◽  
B. J. Bassam ◽  
...  
Keyword(s):  
Root Hair ◽  
Nodulation Genes ◽  
Hair Curling ◽  
Root Hair Curling ◽  
Rhizobium Nodulation

Studies on the Root Hair "Curling Factor" of Rhizobium

1970 ◽  
Vol 131 (4) ◽  
pp. 337-342 ◽  
Author(s):  
D. H. Hubbell
Keyword(s):  
Root Hair ◽  
Hair Curling ◽  
Root Hair Curling

Research Note: Boron deficiency affects early infection events in the pea-Rhizobium symbiotic interaction

2001 ◽  
Vol 28 (8) ◽  
pp. 819 ◽  
Author(s):  
Miguel Redondo-Nieto ◽  
Rafael Rivilla ◽  
Abdelaziz El-Hamdaoui ◽  
Ildefonso Bonilla ◽  
Luis Bolaños
Keyword(s):  
Gene Expression ◽  
Pisum Sativum ◽  
Cell Invasion ◽  
Root Hair ◽  
Boron Deficiency ◽  
Symbiotic Interaction ◽  
Pisum Sativum L ◽  
Plant Exudates ◽  
Hair Curling ◽  
Root Hair Curling

The effects of the deprivation of boron (B) on Rhizobium–legume signaling and preinfection events have been investigated in pea (Pisum sativum L. cv. Argona). The capacity of root exudates to induce the activity of nodulation genes was modulated by B nutrition in the host plant. Exudates derived from B-deficient pea plants led to a low level of nod-gene expression that could be correlated with poor root hair curling. However, inoculation of B-deficient plants with bacteria grown in the presence of the nod-gene inducing hesperetin, restored root hair curling. The attachment of bacteria to roots was also diminished in plants grown in the absence of the micronutrient, and it was not recovered by hesperetin. Both phenomena provoked a reduction in nodulation of more than 50%. Furthermore, infection thread development was arrested at very early stages, and cell invasion by endocytosis was precluded, leading to almost empty of bacteria B-deficient nodules.

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