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Concerted modulation of alanine and glutamate metabolism in young Medicago truncatula seedlings under hypoxic stress.

ABSTRACT: The modulation of primary nitrogen metabolism by hypoxic stress was studied in young Medicago truncatula seedlings. Hypoxic seedlings were characterized by the up-regulation of glutamate dehydrogenase 1 (GDH1) and mitochondrial alanine aminotransferase (mAlaAT), and down-regulation of glutamine synthetase 1b (GS1b), NADH-glutamate synthase (NADH-GOGAT), glutamate dehydrogenase 3 (GDH3), and isocitrate dehydrogenase (ICDH) gene expression. Hypoxic stress severely inhibited GS activity and stimulated NADH-GOGAT activity. GDH activity was lower in hypoxic seedlings than in the control, however, under either normoxia or hypoxia, the in vivo activity was directed towards glutamate deamination. (15)NH(4) labelling showed for the first time that the adaptive reaction of the plant to hypoxia consisted of a concerted modulation of nitrogen flux through the pathways of both alanine and glutamate synthesis. In hypoxic seedlings, newly synthesized (15)N-alanine increased and accumulated as the major amino acid, asparagine synthesis was inhibited, while (15)N-glutamate was synthesized at a similar rate to that in the control. A discrepancy between the up-regulation of GDH1 expression and the down-regulation of GDH activity by hypoxic stress highlighted for the first time the complex regulation of this enzyme by hypoxia. Higher rates of glycolysis and ethanol fermentation are known to cause the fast depletion of sugar stores and carbon stress. It is proposed that the expression of GDH1 was stimulated by hypoxia-induced carbon stress, while the enzyme protein might be involved during post-hypoxic stress contributing to the regeneration of 2-oxoglutarate via the GDH shunt.

SUBMITTER: Limami AM

PROVIDER: S-EPMC2423662 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Herbivore-induced terpenoid emission in Medicago truncatula: concerted action of jasmonate, ethylene and calcium signaling.

Project description:Plant volatiles emitted by Medicago truncatula in response to feeding larvae of Spodoptera exigua are composed of a complex blend of terpenoids. The cDNAs of three terpene synthases (TPSs), which contribute to the blend of terpenoids, were cloned from M. truncatula. Their functional characterization proved MtTPS1 to be a beta-caryophyllene synthase and MtTPS5 to be a multi-product sesquiterpene synthase. MtTPS3 encodes a bifunctional enzyme producing (E)-nerolidol and geranyllinalool (precursors of C11 and C16 homoterpenes) from different prenyl diphosphates serving as substrates. The addition of jasmonic acid (JA) induced expression of the TPS genes, but terpenoid emission was higher from plants treated with JA and the ethylene precursor 1-amino-cyclopropyl-1-carboxylic acid. Compared to infested wild-type M. truncatula plants, lower amounts of various sesquiterpenes and a C11-homoterpene were released from an ethylene-insensitive mutant skl. This difference coincided with lower transcript levels of MtTPS5 and of 1-deoxy-D: -xylulose-5-phosphate synthase (MtDXS2) in the damaged skl leaves. Moreover, ethephon, an ethylene-releasing compound, modified the extent and mode of the herbivore-stimulated Ca2+ variations in the cytoplasm that is necessary for both JA and terpene biosynthesis. Thus, ethylene contributes to the herbivory-induced terpenoid biosynthesis at least twice: by modulating both early signaling events such as cytoplasmic Ca2+-influx and the downstream JA-dependent biosynthesis of terpenoids.

| S-EPMC2756395 | biostudies-literature

Effects of salt stress on Medicago truncatula seedlings

Project description:This SuperSeries is composed of the SubSeries listed below.

2009-11-11 | GSE14029 | GEO

Response of Medicago truncatula seedlings to colonization by Salmonella enterica and Escherichia coli O157:H7.

Project description:Disease outbreaks due to the consumption of legume seedlings contaminated with human enteric bacterial pathogens like Escherichia coli O157:H7 and Salmonella enterica are reported every year. Besides contaminations occurring during food processing, pathogens present on the surface or interior of plant tissues are also responsible for such outbreaks. In the present study, surface and internal colonization of Medicago truncatula, a close relative of alfalfa, by Salmonella enterica and Escherichia coli O157:H7 were observed even with inoculum levels as low as two bacteria per plant. Furthermore, expression analyses revealed that approximately 30% of Medicago truncatula genes were commonly regulated in response to both of these enteric pathogens. This study highlights that very low inoculum doses trigger responses from the host plant and that both of these human enteric pathogens may in part use similar mechanisms to colonize legume seedlings.

| S-EPMC3925098 | biostudies-literature

MtNIP5;1, a novel Medicago truncatula boron diffusion facilitator induced under deficiency.

Project description:Background: Legumes comprise important crops that offer major agronomic benefits, including the capacity of establishing symbiosis with rhizobia, fixing atmospheric N2. It has been proven that legumes are particularly susceptible to boron (B) stress, which leads to important yield penalties. Boron (B) deficiency or toxicity in plants causes the inhibition of growth and an altered development. Under such conditions, the participation of two distinct protein families (the major intrinsic protein family MIP and the Boron transporter family BOR) is required to minimize detrimental effects caused by B stress. However, in legumes, little is known about the transport mechanisms responsible for B uptake and distribution, especially under deficiency.Results: A Medicago truncatula protein, MtNIP5;1 (Medtr1g097840) (homologous to the Arabidopsis thaliana AtNIP5;1) was identified as a novel legume B transporter involved in B uptake under deficiency. Further analyses revealed that this M. truncatula aquaporin expression was boron-regulated in roots, being induced under deficiency and repressed under toxicity. It localizes at the plasma membrane of root epidermal cells and in nodules, where B plays pivotal roles in symbiosis. Furthermore, the partial complementation of the nip5;1-1 A. thaliana mutant phenotype under B deficiency supports a functional role of MtNIP5;1 as a B transporter in this legume model plant.Conclusions: The results here presented support a functional role of MtNIP5;1 in B uptake under deficiency and provides new insights into B transport mechanisms in legume species.

| S-EPMC7724820 | biostudies-literature

Medicago truncatula seed development under greenhouse conditions

Project description:Transcriptional profiling of seeds of Medicago truncatula during maturation. To identify genes that are regulated during seed maturation in the model legume Medicago truncatula, plants at flowering stage were grown at variable light and temperature conditions under greenhouse environment (period March-June). Seeds were then collected at different stages of development. Using the Medicago NimbleGen chip, a transcriptomic analysis was performed to follow the differential expression of genes during seed maturation.

2019-09-11 | GSE137174 | GEO

Nitrogen modulation of Medicago truncatula resistance to Aphanomyces euteiches depends on plant genotype.

Project description:Nitrogen (N) availability can impact plant resistance to pathogens by the regulation of plant immunity. To better understand the links between N nutrition and plant defence, we analysed the impact of N availability on Medicago truncatula resistance to the root pathogen Aphanomyces euteiches. This oomycete is considered to be the most limiting factor for legume production. Ten plant genotypes were tested in vitro for their resistance to A. euteiches in either complete or nitrate-deficient medium. N deficiency led to enhanced or reduced susceptibility depending on the plant genotype. Focusing on four genotypes displaying contrasting responses, we determined the impact of N deficiency on plant growth and shoot N concentration, and performed expression analyses on N- and defence-related genes, as well as the quantification of soluble phenolics and different amino acids in roots. Our analyses suggest that N modulation of plant resistance is not linked to plant response to N deprivation or to mechanisms previously identified to be involved in plant resistance. Furthermore, our studies highlight a role of glutamine in mediating the susceptibility to A. euteiches in M. truncatula.

| S-EPMC6638142 | biostudies-literature

Medicago truncatula seed development at under greenhouse conditions

2013-12-05 | GSE52833 | GEO

Medicago truncatula seed development under different growth conditions

Project description:This SuperSeries is composed of the SubSeries listed below.

2013-12-19 | GSE53526 | GEO

Transcriptome Analysis of Leaf Senescence Regulation Under Alkaline Stress in <i>Medicago truncatula</i>.

Project description:In plants, the leaf is an essential photosynthetic organ, and is the primary harvest in forage crops such as alfalfa (Medicago sativa). Premature leaf senescence caused by environmental stress can result in significant yield loss and quality reduction. Therefore, the stay-green trait is important for improving the economic value of forage crops. Alkaline stress can severely damage leaf cells and, consequently, cause leaf senescence. To understand the molecular regulatory mechanisms and identify vital senescence-associated genes under alkaline stress, we used high-throughput sequencing to study transcriptional changes in Medicago truncatula, a model plant for forage crops. We identified 2,165 differentially expressed genes, 985 of which were identical to those in the dark-induced leaf senescence group. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses showed that the 985 genes were mainly enriched in nutrient cycling processes such as cellular amino acid metabolic processes and organic substance catabolic processes, indicating nutrient redistribution. The other 1,180 differentially expressed genes were significantly enriched in the oxidoreductase complex, aerobic respiration, and ion transport. Our analysis showed the two gene sets guiding the coupled physiological and biochemical alterations play different roles under alkaline stress with a coordinated and integrated way. Many transcription factor families were identified from these differentially expressed genes, including MYB, WRKY, bHLH, and NAC which have particular preference involved in stress resistance and regulation of senescence. Our results contribute to the exploration of the molecular regulatory mechanisms of leaf senescence in M. truncatula under alkaline stress and provide new candidate genes for future breeding to improve the biomass and quality of forage crops.

| S-EPMC9096890 | biostudies-literature

An expression database for roots of the model legume Medicago truncatula under salt stress.

Project description:BackgroundMedicago truncatula is a model legume whose genome is currently being sequenced by an international consortium. Abiotic stresses such as salt stress limit plant growth and crop productivity, including those of legumes. We anticipate that studies on M. truncatula will shed light on other economically important legumes across the world. Here, we report the development of a database called MtED that contains gene expression profiles of the roots of M. truncatula based on time-course salt stress experiments using the Affymetrix Medicago GeneChip. Our hope is that MtED will provide information to assist in improving abiotic stress resistance in legumes.DescriptionThe results of our microarray experiment with roots of M. truncatula under 180 mM sodium chloride were deposited in the MtED database. Additionally, sequence and annotation information regarding microarray probe sets were included. MtED provides functional category analysis based on Gene and GeneBins Ontology, and other Web-based tools for querying and retrieving query results, browsing pathways and transcription factor families, showing metabolic maps, and comparing and visualizing expression profiles. Utilities like mapping probe sets to genome of M. truncatula and In-Silico PCR were implemented by BLAT software suite, which were also available through MtED database.ConclusionMtED was built in the PHP script language and as a MySQL relational database system on a Linux server. It has an integrated Web interface, which facilitates ready examination and interpretation of the results of microarray experiments. It is intended to help in selecting gene markers to improve abiotic stress resistance in legumes. MtED is available at http://bioinformatics.cau.edu.cn/MtED/.

| S-EPMC2779821 | biostudies-literature

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