scholarly journals Heterologous Expression of Rhizobial CelC2 Cellulase Impairs Symbiotic Signaling and Nodulation in Medicago truncatula

2018 ◽  
Vol 31 (5) ◽  
pp. 568-575 ◽  
Author(s):  
Marta Robledo ◽  
Esther Menéndez ◽  
Jose Ignacio Jiménez-Zurdo ◽  
Raúl Rivas ◽  
Encarna Velázquez ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Cell Walls ◽  
Rhizobium Leguminosarum ◽  
Root Nodules ◽  
Root Hairs ◽  
Nod Factors ◽  
Model Legume ◽  
Ensifer Meliloti ◽  
Early Nodulin ◽  
The Impact

The infection of legume plants by rhizobia is tightly regulated to ensure accurate bacterial penetration, infection, and development of functionally efficient nitrogen-fixing root nodules. Rhizobial Nod factors (NF) have key roles in the elicitation of nodulation signaling. Infection of white clover roots also involves the tightly regulated specific breakdown of the noncrystalline apex of cell walls in growing root hairs, which is mediated by Rhizobium leguminosarum bv. trifolii cellulase CelC2. Here, we have analyzed the impact of this endoglucanase on symbiotic signaling in the model legume Medicago truncatula. Ensifer meliloti constitutively expressing celC gene exhibited delayed nodulation and elicited aberrant ineffective nodules, hampering plant growth in the absence of nitrogen. Cotreatment of roots with NF and CelC2 altered Ca2+ spiking in root hairs and induction of the early nodulin gene ENOD11. Our data suggest that CelC2 alters early signaling between partners in the rhizobia-legume interaction.

scholarly journals Analysis of Promoter Activity of the Early Nodulin Enod40 in Lotus japonicus

2005 ◽  
Vol 18 (5) ◽  
pp. 414-427 ◽  
Author(s):  
Mette Grønlund ◽  
Andreas Roussis ◽  
Emmanouil Flemetakis ◽  
Nicolette E. M. Quaedvlieg ◽  
Helmi R. M. Schlaman ◽  
...  
Keyword(s):  
Promoter Activity ◽  
Lotus Japonicus ◽  
Root Hairs ◽  
Early Time ◽  
Cellular Level ◽  
Nod Factors ◽  
Root Cortex ◽  
Model Legume ◽  
Early Nodulin ◽  
Nodulin Genes

Our comparative studies on the promoter (pr) activity of Enod40 in the model legume Lotus japonicus in stably transformed GusA reporter lines and in hairy roots of L. japonicus demonstrate a stringent regulation of the Enod40 promoter in the root cortex and root hairs in response to Nod factors. Interestingly, the L. japonicus Enod40-2 promoter fragment also shows symbiotic activity in the reverse orientation. Deletion analyses of the Glycine max (Gm) Enod40 promoter revealed the presence of a minimal region -185 bp upstream of the transcription start. Stable transgenic L. japonicus reporter lines were used in bioassays to test the effect of different compounds on early symbiotic signaling. The responses of prGmEnod40 reporter lines were compared with the responses of L. japonicus (Lj) reporter lines based on the LjNin promoter. Both reporter lines show very early activity postinoculation in root hairs of the responsive zone of the root and later in the dividing cells of nodule primordia. The LjNin promoter was found to be more responsive than the GmEnod40 promoter to Nod factors and related compounds. The use of prGmEnod40 reporter lines to analyze the effect of nodulin genes on the GmEnod40 promoter activity indicates that LJNIN has a positive effect on the regulation of the Enod40 promoter, whereas the latter is not influenced by ectopic overexpression of its own gene product. In addition to pointing to a difference in the regulation of the two nodulin genes Enod40 and Nin during early time points of symbiosis, the bioassays revealed a difference in the response to the synthetic cytokinin 6-benzylaminopurine (BAP) between alfalfa and clover and L. japonicus. In alfalfa and clover, Enod40 expression was induced upon BAP treatment, whereas this seems not to be the case in L. japonicus; these results correlate with effects at the cellular level because BAP can induce pseudonodules in alfalfa and clover but not in L. japonicus. In conclusion, we demonstrate the applicability of the described L. japonicus reporter lines in analyses of the specificity of compounds related to nodulation as well as for the dissection of the interplay between different nodulin genes.

scholarly journals Glutathione and Homoglutathione Play a Critical Role in the Nodulation Process of Medicago truncatula

2005 ◽  
Vol 18 (3) ◽  
pp. 254-259 ◽  
Author(s):  
Pierre Frendo ◽  
Judith Harrison ◽  
Christel Norman ◽  
María Jesús Hernández Jiménez ◽  
Ghislaine Van de Sype ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Root Nodules ◽  
Critical Role ◽  
Specific Inhibitor ◽  
Buthionine Sulfoximine ◽  
Infection Process ◽  
Symbiotic Interaction ◽  
Transgenic Roots ◽  
Model Legume ◽  
Early Nodulin

Legumes form a symbiotic interaction with bacteria of the Rhizobiaceae family toproduce nitrogen-fixing root nodules under nitrogen-limiting conditions. This process involves the recognition of the bacterial Nod factors by the plant which mediates the entry of the bacteria into the root and nodule organogenesis. We have examined the importance of the low molecular weight thiols, glutathione (GSH) and homoglutathione (hGSH), during the nodulation process in the model legume Medicago truncatula. Using both buthionine sulfoximine, a specific inhibitor of GSH and hGSH synthesis, and transgenic roots expressing GSH synthetase and hGSH synthetase in an antisense orientation, we showed that deficiency in GSH and hGSH synthesis inhibited the formation of the root nodules. This inhibition was not correlated to a modification in the number of infection events or to a change in the expression of the Rhizobium sp.-induced peroxidase rip1, indicating that the low level of GSH or hGSH did not alter the first steps of the infection process. In contrast, a strong diminution in the number of nascent nodules and in the expression of the early nodulin genes, Mtenod12 and Mtenod40, were observed in GSHand hGSH-depleted plants. In conclusion, GSH and hGSH appear to be essential for proper development of the root nodules during the symbiotic interaction.

scholarly journals The Early Nodulin Gene MtN6 Is a Novel Marker for Events Preceding Infection of Medicago truncatula Roots by Sinorhizobium meliloti

1999 ◽  
Vol 12 (6) ◽  
pp. 544-555 ◽  
Author(s):  
R. Mathis ◽  
C. Grosjean ◽  
F. de Billy ◽  
T. Huguet ◽  
P. Gamas
Keyword(s):  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Root Nodules ◽  
Cdna Clones ◽  
Specific Marker ◽  
Nod Factors ◽  
Cortical Cells ◽  
Infection Threads ◽  
Early Nodulin ◽  
Cell Layers

MtN6 belongs to a series of cDNA clones representing Medicago truncatula genes transcriptionally activated during nodulation by Sinorhizobium meliloti (P. Gamas, F. de Carvalho Niebel, N. Lescure, and J. V. Cullimore, Mol. Plant-Microbe Interact. 9:233–242, 1996). We show here by in situ hybridization that MtN6 transcripts specifically accumulate first at very localized regions in the outer root cell layers, corresponding to outer cortical cells containing preinfection threads. At later stages, MtN6 expression is observed ahead of growing infection threads, including in the infection zone of mature root nodules. Interestingly, regulation of MtN6 is clearly distinct from that of other early nodulins expressed in the same region of the nodule, in terms of response to bacterial symbiotic mutants and to purified Nod factors. We thus suggest that MtN6 represents the first specific marker of a pathway involved in preparation to infection, which is at least partly controlled by Nod factors. Finally, we discuss the intriguing sequence homology shown by MtN6 to a protein from Emericella (Aspergillus) nidulans, FluG, that plays a key role in controlling the organogenesis of conidiophores (B. N. Lee and T. H. Adams, Genes Dev. 8:641–651, 1994).

scholarly journals Comparison of nodule endophyte composition, diversity, and gene content between Medicago truncatula genotypes

2021 ◽  
Author(s):  
Mannix Burns ◽  
Brendan Epstein ◽  
Liana Burghardt
Keyword(s):  
Functional Groups ◽  
Medicago Truncatula ◽  
Root Nodules ◽  
Bacterial Endophytes ◽  
Host Genotype ◽  
Model Legume ◽  
Symbiotic Relationships ◽  
Functional Assays ◽  
Altered Gene ◽  
Significant Direct Effect

Leguminous plants form symbiotic relationships with rhizobia. These nitrogen-fixing bacteria live in specialized root organs called nodules. While rhizobia form the most notable host relationship within root nodules, other bacterial endophytes also inhabit these root nodules and can influence host-rhizobia interactions as well as exert effects of their own, whether beneficial or detrimental. In this study, we investigate differences in nodule communities between genotypes (A17 and R108) of a single plant species, the model legume Medicago truncatula. While diversity of endophytes in nodules was similar across hosts, both nodule endophyte composition and gene functional groups differed. In contrast to the significant direct effect of host genotype, neither the presence nor identity of a host in the previous generation (either A17 or R108) had a significant effect on the nodule endophyte diversity or composition. However, whether or not a host was present altered gene functional groups. We conclude that genetic variation within a legume host species can play an important role in the establishment of nodule microbiomes. Further studies, including GWAS and functional assays, can open the door for engineering and optimizing nodule endophyte communities that promote growth or have other beneficial qualities.

The Impact of Simulated Microgravity on the Growth of Different Genotypes of the Model Legume Plant Medicago truncatula

2018 ◽  
Vol 30 (4) ◽  
pp. 491-502 ◽  
Author(s):  
Gemma Lionheart ◽  
Joshua P. Vandenbrink ◽  
Jason D. Hoeksema ◽  
John Z. Kiss
Keyword(s):  
Medicago Truncatula ◽  
Simulated Microgravity ◽  
Model Legume ◽  
Legume Plant ◽  
The Impact

scholarly journals Sinorhizobium meliloti Controls Nitric Oxide–Mediated Post-Translational Modification of a Medicago truncatula Nodule Protein

2015 ◽  
Vol 28 (12) ◽  
pp. 1353-1363 ◽  
Author(s):  
Pauline Blanquet ◽  
Liliana Silva ◽  
Olivier Catrice ◽  
Claude Bruand ◽  
Helena Carvalho ◽  
...  
Keyword(s):  
Nitric Oxide ◽  
Nitrogen Fixation ◽  
Medicago Truncatula ◽  
Sinorhizobium Meliloti ◽  
Molecular Mechanisms ◽  
Root Nodules ◽  
Plant Protein ◽  
Post Translational Modification ◽  
Model Legume ◽  
Bacterial Mutants

Nitric oxide (NO) is involved in various plant-microbe interactions. In the symbiosis between soil bacterium Sinorhizobium meliloti and model legume Medicago truncatula, NO is required for an optimal establishment of the interaction but is also a signal for nodule senescence. Little is known about the molecular mechanisms responsible for NO effects in the legume-rhizobium interaction. Here, we investigate the contribution of the bacterial NO response to the modulation of a plant protein post-translational modification in nitrogen-fixing nodules. We made use of different bacterial mutants to finely modulate NO levels inside M. truncatula root nodules and to examine the consequence on tyrosine nitration of the plant glutamine synthetase, a protein responsible for assimilation of the ammonia released by nitrogen fixation. Our results reveal that S. meliloti possesses several proteins that limit inactivation of plant enzyme activity via NO-mediated post-translational modifications. This is the first demonstration that rhizobia can impact the course of nitrogen fixation by modulating the activity of a plant protein.

scholarly journals Identical Accumulation and Immobilization of Sulfated and Nonsulfated Nod Factors in Host and Nonhost Root Hair Cell Walls

2003 ◽  
Vol 16 (10) ◽  
pp. 884-892 ◽  
Author(s):  
Joachim Goedhart ◽  
Jean-Jacques Bono ◽  
Ton Bisseling ◽  
Theodorus W. J. Gadella
Keyword(s):  
Hair Cell ◽  
Root Hair ◽  
Cell Walls ◽  
Root Hairs ◽  
Sharp Decrease ◽  
Biologically Active ◽  
Nod Factors ◽  
Nod Factor ◽  
Root Hair Cell ◽  
Root Hair Deformation

Nod factors are signaling molecules secreted by Rhizobium bacteria. These lipo-chitooligosaccharides (LCOs) are required for symbiosis with legumes and can elicit specific responses at subnanomolar concentrations on a compatible host. How plants perceive LCOs is unclear. In this study, using fluorescent Nod factor analogs, we investigated whether sulfated and nonsulfated Nod factors were bound and perceived differently by Medicago truncatula and Vicia sativa root hairs. The bioactivity of three novel sulfated fluorescent LCOs was tested in a root hair deformation assay on M. truncatula, showing bioactivity down to 0.1 to 1 nM. Fluorescence microscopy of plasmolyzed M. truncatula root hairs shows that sulfated fluorescent Nod factors accumulate in the cell wall of root hairs, whereas they are absent from the plasma membrane when applied at 10 nM. When the fluorescent Nod factor distribution in medium surrounding a root was studied, a sharp decrease in fluorescence close to the root hairs was observed, visualizing the remarkable capacity of root hairs to absorb Nod factors from the medium. Fluorescence correlation microscopy was used to study in detail the mobilities of sulfated and nonsulfated fluorescent Nod factors which are biologically active on M. truncatula and V. sativa, respectively. Remarkably, no difference between sulfated and nonsulfated Nod factors was observed: both hardly diffuse and strongly accumulate in root hair cell walls of both M. truncatula and V. sativa. The implications for the mode of Nod factor perception are discussed.

scholarly journals The Signal Peptide of the Medicago truncatula Modular Nodulin MtNOD25 Operates as an Address Label for the Specific Targeting of Proteins to Nitrogen-Fixing Symbiosomes

2009 ◽  
Vol 22 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Natalija Hohnjec ◽  
Frauke Lenz ◽  
Vera Fehlberg ◽  
Martin F. Vieweg ◽  
Markus C. Baier ◽  
...  
Keyword(s):  
Medicago Truncatula ◽  
Signal Peptide ◽  
Root Nodules ◽  
Cellular Level ◽  
Specific Element ◽  
Model Legume ◽  
Specific Targeting ◽  
C Terminus ◽  
Organ Specific ◽  
Infected Cells

The nodule-specific MtNOD25 gene of the model legume Medicago truncatula encodes a modular nodulin composed of different repetitive modules flanked by distinct N- and C-termini. Although similarities are low with respect to all repetitive modules, both the N-terminal signal peptide (SP) and the C-terminus are highly conserved in modular nodulins from different legumes. On the cellular level, MtNOD25 is only transcribed in the infected cells of root nodules, and this activation is mediated by a 299-bp minimal promoter containing an organ-specific element. By expressing mGFP6 translational fusions in transgenic nodules, we show that MtNOD25 proteins are exclusively translocated to the symbiosomes of infected cells. This specific targeting only requires an N-terminal MtNOD25 SP that is highly conserved across a family of legume-specific symbiosome proteins. Our finding sheds light on one possible mechanism for the delivery of host proteins to the symbiosomes of infected root nodule cells and, in addition, defines a short molecular address label of only 24 amino acids whose N-terminal presence is sufficient to translocate proteins across the peribacteroid membrane.

scholarly journals Morphogenesis of root nodules in white clover. II. The effect of mutation in genes nod IJ of the microsymbiont upon the nodule structure

2014 ◽  
Vol 67 (1) ◽  
pp. 5-22
Author(s):  
Barbara Łotocka ◽  
Joanna Kopcińska ◽  
Władysław Golinowski
Keyword(s):  
White Clover ◽  
Rhizobium Leguminosarum ◽  
Root Nodules ◽  
Single Cells ◽  
Wild Strain ◽  
Root Hairs ◽  
Nodule Development ◽  
Wild Type ◽  
Delayed Reaction ◽  
Infection Threads

Morphogenesis of ineffective root nodules initiated on the roots of white clover 'Astra' by the <em>Rhizobium leguminosarum</em> biovar. <em>trifolii</em> strains ANU261 (Tn5 insertion in nod 1 gene) and ANU262 (Tn5 insertion in nod J gene) was investigated. Following changes were observed, as compared to the wild-type nodulation: the exaggerated, not delayed reaction of root hairs; the delay in nodulation with the number of nodules the same as in plants inoculated with a wild strain; the formation and organization of the nodule primordium not changed in comparison with the wild-type nodules; infection threads abnormally branched and diffusing with bacteria deprived of light zone and enriched with storage material; infected cells of bacteroidal tissue abnormally strongly osmiophilic and only slightly vacuolated; symbiosomes with very narrowed peribacteroidal space, subject to premature degradation; abnormal accumulation of starch in the nodule tissues; nodule development blocked at the stage of laterally situated meristem and single nodule bundle; inhibition of divisions in the meristem and vacuolation of its cells; the appearance of single cells with colonies of saprophytic rhizobia embedded in the fibrillar matrix in the old, degraded regions of the bacteroidal tissue.

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