Nod Factor Production by Azorhizobium Caulinodans Strain ORS571

Cultivar Afghanistan peas are resistant to nodulation by many strains of Rhizobium leguminosarum bv. viciae but are nodulated by strain TOM, which carries the host specificity gene nodX. Some strains that lack nodX can inhibit nodulation of cv. Afghanistan by strain TOM. We present evidence that this “competitive nodulation-blocking” (Cnb) phenotype may result from high levels of Nod factors inhibiting nodulation of cv. Afghanistan peas. The TOM nod gene region (including nodX) is cloned on pIJ1095, and strains (including TOM itself) carrying pIJ1095 nodulate cv. Afghanistan peas very poorly but can nodulate other varieties normally. The presence of pIJ1095, which causes increased levels of Nod factor production, correlates with Cnb. Nodulation of cv. Afghanistan by TOM is also inhibited by a cloned nodD gene that increases nod gene expression and Nod factor production. Nodulation of cv. Afghanistan can be stimulated if nodD on pIJ1095 is mutated, thus severely reducing the level of Nod factor produced. Repression of nod gene expression by nolR eliminates the Cnb phenotype and can stimulate nodulation of cv. Afghanistan. Addition of Nod factors to cv. Afghanistan roots strongly inhibits nodulation. The Cnb+ strains and added Nod factors inhibit infection thread initiation by strain TOM. The sym2A allele determines resistance of cv. Afghanistan to nodulation by strains of R. leguminosarum bv. viciae lacking nodX. We tested whether sym2A is involved in Cnb by using a pea line carrying the sym2A region introgressed from cv. Afghanistan; nodulation in the introgressed line was inhibited by Cnb+ strains. Therefore, the sym2A region has an effect on Cnb, although another locus (or loci) may contribute to the stronger Cnb seen in cv. Afghanistan.

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Nod Factors of Azorhizobium caulinodans Strain ORS571 Can Be Glycosylated with an Arabinosyl Group, a Fucosyl Group, or Both

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.1997.10.5.683 ◽

1997 ◽

Vol 10 (5) ◽

pp. 683-687 ◽

Cited By ~ 30

Author(s):

Peter Mergaert ◽

Myriam Ferro ◽

Wim D'Haeze ◽

Marc Van Montagu ◽

Marcelle Holsters ◽

...

Keyword(s):

Relative Proportion ◽

Growth Conditions ◽

Sesbania Rostrata ◽

Nod Factors ◽

Azorhizobium Caulinodans ◽

Nod Factor ◽

Nod Genes ◽

Group A ◽

Root Hair Formation ◽

Hair Formation

In addition to the previously described arabinosylated Nod factors, Azorhizobium caulinodans can also produce fucosylated Nod factors and Nod factors that are both arabinosylated and fucosylated. The presence of a plasmid carrying extra copies of a subset of nod genes as well as bacterial growth conditions influence the relative proportion of carbamoylated, fucosylated, and arabinosylated Nod factors. By using a root hair formation assay, we demonstrate that the Nod factor glycosylations are important for biological activity on Sesbania rostrata roots.

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The nodD1 gene of Sinorhizobium fredii HH103 Restores Nodulation Capacity on Bean in a Rhizobium tropici CIAT 899 nodD1/nodD2 Mutant, but the Secondary Symbiotic Regulators nolR, nodD2 or syrM Prevent HH103 to Nodulate with This Legume

Microorganisms ◽

10.3390/microorganisms10010139 ◽

2022 ◽

Vol 10 (1) ◽

pp. 139

Author(s):

Francisco Fuentes-Romero ◽

Pilar Navarro-Gómez ◽

Paula Ayala-García ◽

Isamar Moyano-Bravo ◽

Francisco-Javier López-Baena ◽

...

Keyword(s):

Nitrogenase Activity ◽

Lotus Japonicus ◽

Rhizobium Tropici ◽

Sinorhizobium Fredii ◽

Symbiotic Interaction ◽

Model Legume ◽

Nod Factor ◽

Factor Production ◽

Nodulation Capacity ◽

Type 3

Rhizobial NodD proteins and appropriate flavonoids induce rhizobial nodulation gene expression. In this study, we show that the nodD1 gene of Sinorhizobium fredii HH103, but not the nodD2 gene, can restore the nodulation capacity of a double nodD1/nodD2 mutant of Rhizobium tropici CIAT 899 in bean plants (Phaseolus vulgaris). S. fredii HH103 only induces pseudonodules in beans. We have also studied whether the mutation of different symbiotic regulatory genes may affect the symbiotic interaction of HH103 with beans: ttsI (the positive regulator of the symbiotic type 3 protein secretion system), and nodD2, nolR and syrM (all of them controlling the level of Nod factor production). Inactivation of either nodD2, nolR or syrM, but not that of ttsI, affected positively the symbiotic behavior of HH103 with beans, leading to the formation of colonized nodules. Acetylene reduction assays showed certain levels of nitrogenase activity that were higher in the case of the nodD2 and nolR mutants. Similar results have been previously obtained by our group with the model legume Lotus japonicus. Hence, the results obtained in the present work confirm that repression of Nod factor production, provided by either NodD2, NolR or SyrM, prevents HH103 to effectively nodulate several putative host plants.

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Root nodulation of Sesbania rostrata suppresses stem nodulation by Sinorhizobium teranga but not Azorhizobium caulinodans

Canadian Journal of Microbiology ◽

10.1139/m96-028 ◽

1996 ◽

Vol 42 (2) ◽

pp. 187-190 ◽

Cited By ~ 9

Author(s):

Kodjo Tomekpe ◽

Marcelle Holsters ◽

Bernard Dreyfus

Keyword(s):

Host Plant ◽

Root Nodules ◽

Sesbania Rostrata ◽

Efficient Production ◽

Nod Factors ◽

Azorhizobium Caulinodans ◽

Experimental Conditions ◽

Nod Factor ◽

Stem Nodulation ◽

Azorhizobium Caulinodans Ors571

Azorhizobium caulinodans ORS571 and Sinorhizobium teranga ORS51 and ORS52 are symbionts of the same host plant Sesbania rostrata. In nature, A. caulinodans nodulates more competitively the stem-located infection sites of Sesbania rostrata. Sinorhizobium strains, although frequently present in root nodules, are seldom found in stem nodules. One probable explanation for this phenomenon is the more abundant presence of Azorhizobium on the leaf and stem surfaces of the host plant. Work presented here hints at other plausible factors that determine the greater "stem specificity" of Azorhizobium. We found that under experimental conditions in which roots are not inoculated, all strains nodulated stems very well. However, ORS51 and ORS52 were much more sensitive than ORS571 to suppression of stem nodulation by previous root inoculation. The introduction of the regulatory nodD gene from A. caulinodans diminished the sensitivity to this suppression, probably by enhanced nod gene expression and subsequent Nod factor production. Our hypothesis is that the greater infectivity of ORS571 is due to a more efficient production of mitogenic Nod factors at stem-located infection sites, thereby more readily overcoming systemic suppression caused by previous root inoculations.Key words: autoregulation, nitrogen fixation, rhizobial ecology, systemic suppression of nodulation.

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