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Delayed maturation of nodules reduces symbiotic effectiveness of the Lotus japonicus-Rhizobium sp. NGR234 interaction.

Schumpp O, Crèvecoeur M, Broughton WJ, Deakin WJ - J. Exp. Bot. (2008)

Bottom Line: It was found that NGR234 initiates nodule formation in a similar way to M. loti MAFF303099, but that the nodules which develop on eleven L. japonicus ecotypes are less efficient in fixing nitrogen.With time, these nodules develop into fully efficient organs containing bacteroids tightly enclosed in symbiosome membranes, just like those formed by M. loti MAFF303099.This work demonstrates the usefulness of using the well-characterized micro-symbiont NGR234 to study symbiotic signal exchange in the later stages of rhizobia-legume symbioses, especially given the large range of bacterial (NGR234) and plant (L. japonicus) mutants that are available.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Biologie Moléculaire des Plantes Supérieures, Université de Genève, 30 Quai Ernest-Ansermet, Sciences III, CH-1211 Genève 4, Switzerland.

ABSTRACT
Lotus japonicus, a model legume, develops an efficient, nitrogen-fixing symbiosis with Mesorhizobium loti that promotes plant growth. Lotus japonicus also forms functional nodules with Rhizobium sp. NGR234 and R. etli. Yet, in a plant defence-like reaction, nodules induced by R. etli quickly degenerate, thus limiting plant growth. In contrast, nodules containing NGR234 are long-lasting. It was found that NGR234 initiates nodule formation in a similar way to M. loti MAFF303099, but that the nodules which develop on eleven L. japonicus ecotypes are less efficient in fixing nitrogen. Detailed examination of nodulation of L. japonicus cultivar MG-20 revealed that symbiosomes formed four weeks after inoculation by NGR234 are enlarged in comparison with MAFF303099 and contain multiple bacteroids. Nevertheless, nodules formed by NGR234 fix sufficient nitrogen to avoid rejection by the plant. With time, these nodules develop into fully efficient organs containing bacteroids tightly enclosed in symbiosome membranes, just like those formed by M. loti MAFF303099. This work demonstrates the usefulness of using the well-characterized micro-symbiont NGR234 to study symbiotic signal exchange in the later stages of rhizobia-legume symbioses, especially given the large range of bacterial (NGR234) and plant (L. japonicus) mutants that are available.

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Related in: MedlinePlus

Early steps of nodule development in Lotus inoculated with NGR234 or MAFF303099. (A) Quantification of nodules formed: nodules were counted 4 wpi. Bars represent standard deviations from the mean of four pots containing three plants each. (B) Infection thread development by MAFF303099 and NGR234 strains labelled with GFP. (C) Expression of early nodulins 4 wpi. Transcript levels were measured from complete root systems by quantitative PCR, relative to mock-inoculated (with MgSO4) roots, using ATP synthase as an internal control.
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fig2: Early steps of nodule development in Lotus inoculated with NGR234 or MAFF303099. (A) Quantification of nodules formed: nodules were counted 4 wpi. Bars represent standard deviations from the mean of four pots containing three plants each. (B) Infection thread development by MAFF303099 and NGR234 strains labelled with GFP. (C) Expression of early nodulins 4 wpi. Transcript levels were measured from complete root systems by quantitative PCR, relative to mock-inoculated (with MgSO4) roots, using ATP synthase as an internal control.

Mentions: At 4 wpi, MG-20 plants inoculated with NGR234 formed slightly fewer nodules relative to plants inoculated with MAFF303099. A significant proportion of these nodules were green (presumably ineffective) however (Fig. 2A). To determine whether there were any obvious differences in infection thread development, both rhizobial strains were labelled with green fluorescent protein (GFP). Classic infection threads were observed with both bacteria that extended from the infection pocket of a deformed root hair towards the inner part of the root (Fig. 2B). Initiation of nodule development was also analysed at the molecular level by measuring the expression of two well studied genes induced early in nodule organogenesis; Enod2 and the gene encoding leghaemoglobin. RNA was extracted from whole roots 4 wpi, and expression levels determined in MG-20 plants inoculated with NGR234 or MAFF303099. Both genes were expressed at similar levels in both plants (Fig. 2C).


Delayed maturation of nodules reduces symbiotic effectiveness of the Lotus japonicus-Rhizobium sp. NGR234 interaction.

Schumpp O, Crèvecoeur M, Broughton WJ, Deakin WJ - J. Exp. Bot. (2008)

Early steps of nodule development in Lotus inoculated with NGR234 or MAFF303099. (A) Quantification of nodules formed: nodules were counted 4 wpi. Bars represent standard deviations from the mean of four pots containing three plants each. (B) Infection thread development by MAFF303099 and NGR234 strains labelled with GFP. (C) Expression of early nodulins 4 wpi. Transcript levels were measured from complete root systems by quantitative PCR, relative to mock-inoculated (with MgSO4) roots, using ATP synthase as an internal control.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2651464&req=5

fig2: Early steps of nodule development in Lotus inoculated with NGR234 or MAFF303099. (A) Quantification of nodules formed: nodules were counted 4 wpi. Bars represent standard deviations from the mean of four pots containing three plants each. (B) Infection thread development by MAFF303099 and NGR234 strains labelled with GFP. (C) Expression of early nodulins 4 wpi. Transcript levels were measured from complete root systems by quantitative PCR, relative to mock-inoculated (with MgSO4) roots, using ATP synthase as an internal control.
Mentions: At 4 wpi, MG-20 plants inoculated with NGR234 formed slightly fewer nodules relative to plants inoculated with MAFF303099. A significant proportion of these nodules were green (presumably ineffective) however (Fig. 2A). To determine whether there were any obvious differences in infection thread development, both rhizobial strains were labelled with green fluorescent protein (GFP). Classic infection threads were observed with both bacteria that extended from the infection pocket of a deformed root hair towards the inner part of the root (Fig. 2B). Initiation of nodule development was also analysed at the molecular level by measuring the expression of two well studied genes induced early in nodule organogenesis; Enod2 and the gene encoding leghaemoglobin. RNA was extracted from whole roots 4 wpi, and expression levels determined in MG-20 plants inoculated with NGR234 or MAFF303099. Both genes were expressed at similar levels in both plants (Fig. 2C).

Bottom Line: It was found that NGR234 initiates nodule formation in a similar way to M. loti MAFF303099, but that the nodules which develop on eleven L. japonicus ecotypes are less efficient in fixing nitrogen.With time, these nodules develop into fully efficient organs containing bacteroids tightly enclosed in symbiosome membranes, just like those formed by M. loti MAFF303099.This work demonstrates the usefulness of using the well-characterized micro-symbiont NGR234 to study symbiotic signal exchange in the later stages of rhizobia-legume symbioses, especially given the large range of bacterial (NGR234) and plant (L. japonicus) mutants that are available.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Biologie Moléculaire des Plantes Supérieures, Université de Genève, 30 Quai Ernest-Ansermet, Sciences III, CH-1211 Genève 4, Switzerland.

ABSTRACT
Lotus japonicus, a model legume, develops an efficient, nitrogen-fixing symbiosis with Mesorhizobium loti that promotes plant growth. Lotus japonicus also forms functional nodules with Rhizobium sp. NGR234 and R. etli. Yet, in a plant defence-like reaction, nodules induced by R. etli quickly degenerate, thus limiting plant growth. In contrast, nodules containing NGR234 are long-lasting. It was found that NGR234 initiates nodule formation in a similar way to M. loti MAFF303099, but that the nodules which develop on eleven L. japonicus ecotypes are less efficient in fixing nitrogen. Detailed examination of nodulation of L. japonicus cultivar MG-20 revealed that symbiosomes formed four weeks after inoculation by NGR234 are enlarged in comparison with MAFF303099 and contain multiple bacteroids. Nevertheless, nodules formed by NGR234 fix sufficient nitrogen to avoid rejection by the plant. With time, these nodules develop into fully efficient organs containing bacteroids tightly enclosed in symbiosome membranes, just like those formed by M. loti MAFF303099. This work demonstrates the usefulness of using the well-characterized micro-symbiont NGR234 to study symbiotic signal exchange in the later stages of rhizobia-legume symbioses, especially given the large range of bacterial (NGR234) and plant (L. japonicus) mutants that are available.

Show MeSH
Related in: MedlinePlus