Full-Size ABC Transporters from the ABCG Subfamily in Medicago truncatula

Full-size ATP-binding cassette (ABC) transporters belonging to the ABCG subfamily are unique for plants and fungi. There is growing evidence that certain of these proteins play a role in plant defense or signaling systems. As yet, a complete set of full-size ABCG protein genes has been inventoried and classified in only two plants: Arabidopsis thaliana and Oryza sativa. Recently, a domain-based clustering analysis has predicted the presence of at least 12 genes encoding such proteins in the Lotus japonicus genome. Here, we identify and classify 19 genes coding full-size ABCG proteins in Medicago truncatula, a model legume plant. We have found that the majority of these genes are expressed in roots and flowers whereas only a few are expressed in leaves. Expression of several has been induced upon pathogenic infection in both roots and leaves. ABCG messenger RNAs have been detected in root nodules forming during symbiosis of legume plants and nitrogen-fixing bacteria. The data presented provide a scaffold for further studies of the physiological function of Medicago ABCG transporters and their possible role in modulating plant–microorganism interactions.

Download Full-text

Characterization and Expression Analysis of Genes Encoding Phosphoenolpyruvate Carboxylase and Phosphoenolpyruvate Carboxylase Kinase of Lotus japonicus, a Model Legume

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi.2003.16.4.281 ◽

2003 ◽

Vol 16 (4) ◽

pp. 281-288 ◽

Cited By ~ 19

Author(s):

Tomomi Nakagawa ◽

Tomoko Izumi ◽

Mari Banba ◽

Yosuke Umehara ◽

Hiroshi Kouchi ◽

...

Keyword(s):

Phosphoenolpyruvate Carboxylase ◽

Root Nodules ◽

Expression Patterns ◽

Phosphorylation Site ◽

Lotus Japonicus ◽

Specific Protein ◽

Mrna Levels ◽

Model Legume ◽

Putative Phosphorylation Site

Phosphoenolpyruvate carboxylases (PEPCs), one form of which in each legume species plays a central role in the carbon metabolism in symbiotic root nodules, are activated through phosphorylation of a conserved residue by a specific protein kinase (PEPC-PK). We characterized the cDNAs for two PEPC isoforms of Lotus japonicus, an amide-translocating legume that forms determinate nodules. One gene encodes a nodule-enhanced form, which is more closely related to the PEPCs in amide-type indeterminate nodules than those in ureide-type determinate nodules. The other gene is expressed in shoots and roots at a low level. Both forms have the putative phosphorylation site, Ser11. We also isolated a cDNA and the corresponding genomic DNA for PEPC-PK of L. japonicus. The recombinant PEPC-PK protein expressed in Escherichia coli phosphorylated recombinant maize C4-form PEPC efficiently in vitro. The level of mRNA for PEPC-PK was high in root nodules, and those in shoots and roots were also significant. In situ hybridization revealed that the expression patterns of the transcripts for PEPC and PEPC-PK were similar in mature root nodules, but were different in emerging nodules. When L. japonicus seedlings were subjected to prolonged darkness and subsequent illumination, the activity of PEPC-PK and the mRNA levels of both PEPC and PEPC-PK in nodules decreased and then recovered, suggesting that they are regulated according to the amounts of photosynthates transported from shoots.

Download Full-text

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

Phytobiomes Journal ◽

10.1094/pbiomes-10-20-0077-r ◽

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.

Download Full-text

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

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-11-17-0265-r ◽

2018 ◽

Vol 31 (5) ◽

pp. 568-575 ◽

Cited By ~ 5

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.

Download Full-text

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

Microgravity Science and Technology ◽

10.1007/s12217-018-9619-4 ◽

2018 ◽

Vol 30 (4) ◽

pp. 491-502 ◽

Cited By ~ 2

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

Download Full-text

Isolation and Phetypic Characterization of Anthocyanin Pigmentation Mutants in the Model Legume Plant Medicago Truncatula

10.46678/pb.20.365246 ◽

2020 ◽

Author(s):

Vijaykumar Veerappan

Keyword(s):

Medicago Truncatula ◽

Anthocyanin Pigmentation ◽

Model Legume ◽

Legume Plant

Download Full-text

Genome-wide analysis of ATP-binding cassette (ABC) proteins in a model legume plant, Lotus japonicus: comparison with Arabidopsis ABC protein family

DNA Research ◽

10.1093/dnares/dsl013 ◽

2006 ◽

Vol 13 (5) ◽

pp. 205-228 ◽

Cited By ~ 41

Author(s):

Akifumi Sugiyama ◽

Nobukazu Shitan ◽

Shusei Sato ◽

Yasukazu Nakamura ◽

Satoshi Tabata ◽

...

Keyword(s):

Lotus Japonicus ◽

Protein Family ◽

Atp Binding ◽

Abc Proteins ◽

Model Legume ◽

Genome Wide Analysis ◽

Abc Protein ◽

Genome Wide ◽

Legume Plant ◽

Atp Binding Cassette

Download Full-text

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

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-05-15-0118-r ◽

2015 ◽

Vol 28 (12) ◽

pp. 1353-1363 ◽

Cited By ~ 21

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.

Download Full-text

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

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-22-1-0063 ◽

2009 ◽

Vol 22 (1) ◽

pp. 63-72 ◽

Cited By ~ 16

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.

Download Full-text

Guarding the gateway to histidine biosynthesis in plants: Medicago truncatula ATP-phosphoribosyltransferase in relaxed and tense states

Biochemical Journal ◽

10.1042/bcj20180289 ◽

2018 ◽

Vol 475 (16) ◽

pp. 2681-2697

Author(s):

Milosz Ruszkowski

Keyword(s):

Medicago Truncatula ◽

Feedback Inhibition ◽

Histidine Biosynthesis ◽

Peptide Backbone ◽

Model Legume ◽

Regulatory Domains ◽

Legume Plant ◽

Eukaryotic Organism ◽

Α Helix ◽

T State

In the first committed step of histidine biosynthesis, adenosine 5′-triphosphate (ATP) and 5-phosphoribosyl-α1-pyrophosphate (PRPP), in the presence of ATP phosphoribosyltransferase (ATP-PRT, EC 2.4.2.17), yield phosphoribosyl-ATP. ATP-PRTs are subject to feedback inhibition by histidine that allosterically binds between the regulatory domains. Histidine biosynthetic pathways of bacteria, lower eukaryotes, and plants are considered promising targets for the design of antibiotics, antifungal agents, and herbicides because higher organisms are histidine heterotrophs. Plant ATP-PRTs are similar to one of the two types of their bacterial counterparts, the long-type ATP-PRTs. A biochemical and structural study of ATP-PRT from the model legume plant, Medicago truncatula (MedtrATP-PRT1) is reported herein. Two crystal structures, presenting homohexameric MedtrATP-PRT1 in its relaxed (R-) and histidine-bound, tense (T-) states allowed to observe key features of the enzyme and provided the first structural insights into an ATP-PRT from a eukaryotic organism. In particular, they show pronounced conformational reorganizations during R-state to T-state transition that involves substantial movements of domains. This rearrangement requires a trans- to cis- switch of a peptide backbone within the hinge region of MedtrATP-PRT1. A C-terminal α-helix, absent in bacteria, reinforces the hinge that is constituted by two peptide strands. As a result, conformations of the R- and T-states are significantly different from the corresponding states of prokaryotic enzymes with known 3-D structures. Finally, adenosine 5′-monophosphate (AMP) bound at the active site is consistent with a competitive (and synergistic with histidine) nature of AMP inhibition.

Download Full-text