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

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.

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

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.1998.11.12.1233 ◽

1998 ◽

Vol 11 (12) ◽

pp. 1233-1241 ◽

Cited By ~ 49

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

Functional Plant Biology ◽

10.1071/pp9960285 ◽

1996 ◽

Vol 23 (3) ◽

pp. 285 ◽

Cited By ~ 43

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.

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

Australian Journal of Biological Sciences ◽

10.1071/bi9690413 ◽

1969 ◽

Vol 22 (2) ◽

pp. 413 ◽

Cited By ~ 56

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.

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Endoplasmic reticulum-targeted GFP reveals ER remodeling in Mesorhizobium-treated Lotus japonicus root hairs during root hair curling and infection thread formation

PROTOPLASMA ◽

10.1007/s00709-013-0584-x ◽

2013 ◽

Vol 251 (4) ◽

pp. 817-826 ◽

Cited By ~ 5

Author(s):

F. M. Perrine-Walker ◽

H. Kouchi ◽

R.W. Ridge

Keyword(s):

Endoplasmic Reticulum ◽

Root Hair ◽

Lotus Japonicus ◽

Root Hairs ◽

Infection Thread ◽

Thread Formation ◽

Hair Curling ◽

Root Hair Curling ◽

Infection Thread Formation

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

Development ◽

10.1242/dev.128.9.1507 ◽

2001 ◽

Vol 128 (9) ◽

pp. 1507-1518 ◽

Cited By ~ 7

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.

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Role of Cellulose Fibrils and Exopolysaccharides of Rhizobium leguminosarum in Attachment to and Infection of Vicia sativa Root Hairs

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-18-0533 ◽

2005 ◽

Vol 18 (6) ◽

pp. 533-538 ◽

Cited By ~ 71

Author(s):

M. C. Laus ◽

A. A. N. van Brussel ◽

J. W. Kijne

Keyword(s):

Root Hair ◽

Rhizobium Leguminosarum ◽

Developmental Stages ◽

Cortical Cell ◽

Root Hairs ◽

Infection Thread ◽

Vicia Sativa ◽

Wild Type ◽

Infection Threads ◽

Cellulose Fibrils

Infection and subsequent nodulation of legume host plants by the root nodule symbiote Rhizobium leguminosarum usually require attachment of the bacteria to root-hair tips. Bacterial cellulose fibrils have been shown to be involved in this attachment process but appeared not to be essential for successful nodulation. Detailed analysis of Vicia sativa root-hair infection by wild-type Rhizobium leguminosarum RBL5523 and its cellulose fibril-deficient celE mutant showed that wild-type bacteria infected elongated growing root hairs, whereas cellulose-deficient bacteria infected young emerging root hairs. Exopolysaccharide-deficient strains that retained the ability to produce cellulose fibrils could also infect elongated root hairs but infection thread colonization was defective. Cellulose-mediated agglutination of these bacteria in the root-hair curl appeared to prevent entry into the induced infection thread. Infection experiments with V. sativa roots and an extracellular polysaccharide (EPS)- and cellulose-deficient double mutant showed that cellulose-mediated agglutination of the EPS-deficient bacteria in the infection thread was now abolished and that infection thread colonization was partially restored. Interestingly, in this case, infection threads were initiated in root hairs that originated from the cortical cell layers of the root and not in epidermal root hairs. Apparently, surface polysaccharides of R. leguminosarum, such as cellulose fibrils, are determining factors for infection of different developmental stages of root hairs.

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Identification of Symbiotically Defective Mutants of Lotus japonicus Affected in Infection Thread Growth

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-19-1444 ◽

2006 ◽

Vol 19 (12) ◽

pp. 1444-1450 ◽

Cited By ~ 20

Author(s):

Fabien Lombardo ◽

Anne B. Heckmann ◽

Hiroki Miwa ◽

Jillian A. Perry ◽

Koji Yano ◽

...

Keyword(s):

Root Hair ◽

Plant Cell Wall ◽

Plant Root ◽

Lotus Japonicus ◽

Cortical Cell ◽

Host Cells ◽

Infection Thread ◽

Mycorrhizal Symbiosis ◽

Symbiotic Interaction ◽

Infection Threads

During the symbiotic interaction between legumes and rhizobia, the host cell plasma membrane and associated plant cell wall invaginate to form a tunnel-like infection thread, a structure in which bacteria divide to reach the plant root cortex. We isolated four Lotus japonicus mutants that make infection pockets in root hairs but form very few infection threads after inoculation with Mesorhizobium loti. The few infection threads that did initiate in the mutants usually did not progress further than the root hair cell. These infection-thread deficient (itd) mutants were unaffected for early symbiotic responses such as calcium spiking, root hair deformation, and curling, as well as for the induction of cortical cell division and the arbuscular mycorrhizal symbiosis. Complementation tests and genetic mapping indicate that itd2 is allelic to Ljsym7, whereas the itd1, itd3, and itd4 mutations identified novel loci. Bacterial release into host cells did occur occasionally in the itd1, itd2, and itd3 mutants suggesting that some infections may succeed after a long period and that infection of nodule cells could occur normally if the few abnormal infection threads that were formed reached the appropriate nodule cells.

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