Profiling of spatial metabolite distributions in wheat leaves under normal and nitrate limiting conditions

The control and interaction between nitrogen and carbon assimilatory pathways is essential in both photosynthetic and non-photosynthetic tissue in order to support metabolic processes without compromising growth. Physiological differences between the basal and mature region of wheat (Triticum aestivum) primary leaves confirmed that there was a change from heterotrophic to autotrophic metabolism. Fourier Transform Infrared (FT-IR) spectroscopy confirmed the suitability and phenotypic reproducibility of the leaf growth conditions. Principal Component–Discriminant Function Analysis (PC–DFA) revealed distinct clustering between base, and tip sections of the developing wheat leaf, and from plants grown in the presence or absence of nitrate. Gas Chromatography-Time of Flight/Mass Spectrometry (GC-TOF/MS) combined with multivariate and univariate analyses, and Bayesian network (BN) analysis, distinguished different tissues and confirmed the physiological switch from high rates of respiration to photosynthesis along the leaf. The operation of nitrogen metabolism impacted on the levels and distribution of amino acids, organic acids and carbohydrates within the wheat leaf. In plants grown in the presence of nitrate there was reduced levels of a number of sugar metabolites in the leaf base and an increase in maltose levels, possibly reflecting an increase in starch turnover. The value of using this combined metabolomics analysis for further functional investigations in the future are discussed

Expression of uncoupling proteins-1,-2 and-3 mRNA is induced by an adenocarcinoma-derived lipid-mobilizing factor

The abnormalities of lipid metabolism observed in cancer cachexia may be induced by a lipid-mobilizing factor produced by adenocarcinomas. The specific molecules and metabolic pathways that mediate the actions of lipid-mobilizing factor are not known. The mitochondrial uncoupling proteins-1, -2 and -3 are suggested to play essential roles in energy dissipation and disposal of excess lipid. Here, we studied the effects of lipid-mobilizing factor on the expression of uncoupling proteins-1, -2 and -3 in normal mice. Lipid-mobilizing factor isolated from the urine of cancer patients was injected intravenously into mice over a 52-h period, while vehicle was similarly given to controls. Lipid-mobilizing factor caused significant reductions in body weight (-10%, P=0.03) and fat mass (-20%, P<0.01) accompanied by a marked decrease in plasma leptin (-59%, P<0.01) and heavy lipid deposition in the liver. In brown adipose tissue, uncoupling protein-1 mRNA levels were elevated in lipid-mobilizing factor-treated mice (+96%, P<0.01), as were uncoupling proteins-2 and -3 (+57% and +37%, both P<0.05). Lipid-mobilizing factor increased uncoupling protein-2 mRNA in both skeletal muscle (+146%, P<0.05) and liver (+142%, P=0.03). The protein levels of uncoupling protein-1 in brown adipose tissue and uncoupling protein-2 in liver were also increased with lipid-mobilizing factor administration (+49% and +67%, both P=0.02). Upregulation by lipid-mobilizing factor of uncoupling proteins-1, -2 and -3 in brown adipose tissue, and of uncoupling protein-2 in skeletal muscle and liver, suggests that these uncoupling proteins may serve to utilize excess lipid mobilized during fat catabolism in cancer cachexia

Comparison of Muscle Transcriptome between Pigs with Divergent Meat Quality Phenotypes Identifies Genes Related to Muscle Metabolism and Structure

Background: Meat quality depends on physiological processes taking place in muscle tissue, which could involve a large pattern of genes associated with both muscle structural and metabolic features. Understanding the biological phenomena underlying muscle phenotype at slaughter is necessary to uncover meat quality development. Therefore, a muscle transcriptome analysis was undertaken to compare gene expression profiles between two highly contrasted pig breeds, Large White (LW) and Basque (B), reared in two different housing systems themselves influencing meat quality. LW is the most predominant breed used in pig industry, which exhibits standard meat quality attributes. B is an indigenous breed with low lean meat and high fat contents, high meat quality characteristics, and is genetically distant from other European pig breeds. Methodology/Principal Findings: Transcriptome analysis undertaken using a custom 15 K microarray, highlighted 1233 genes differentially expressed between breeds (multiple-test adjusted P-value,0.05), out of which 635 were highly expressed in the B and 598 highly expressed in the LW pigs. No difference in gene expression was found between housing systems. Besides, expression level of 12 differentially expressed genes quantified by real-time RT-PCR validated microarray data. Functional annotation clustering emphasized four main clusters associated to transcriptome breed differences: metabolic processes, skeletal muscle structure and organization, extracellular matrix, lysosome, and proteolysis, thereb

Modulation of epithelial sodium channel (ENaC) expression in mouse lung infected with Pseudomonas aeruginosa

BACKGROUND: The intratracheal instillation of Pseudomonas aeruginosa entrapped in agar beads in the mouse lung leads to chronic lung infection in susceptible mouse strains. As the infection generates a strong inflammatory response with some lung edema, we tested if it could modulate the expression of genes involved in lung liquid clearance, such as the α, β and γ subunits of the epithelial sodium channel (ENaC) and the catalytic subunit of Na(+)-K(+)-ATPase. METHODS: Pseudomonas aeruginosa entrapped in agar beads were instilled in the lung of resistant (BalB/c) and susceptible (DBA/2, C57BL/6 and A/J) mouse strains. The mRNA expression of ENaC and Na(+)-K(+)-ATPase subunits was tested in the lung by Northern blot following a 3 hours to 14 days infection. RESULTS: The infection of the different mouse strains evoked regulation of α and β ENaC mRNA. Following Pseudomonas instillation, the expression of αENaC mRNA decreased to a median of 43% on days 3 and 7 after infection and was still decreased to a median of 45% 14 days after infection (p < 0.05). The relative expression of βENaC mRNA was transiently increased to a median of 241%, 24 h post-infection before decreasing to a median of 43% and 54% of control on days 3 and 7 post-infection (p < 0.05). No significant modulation of γENaC mRNA was detected although the general pattern of expression of the subunit was similar to α and β subunits. No modulation of α(1)Na(+)-K(+)-ATPase mRNA, the catalytic subunit of the sodium pump, was recorded. The distinctive expression profiles of the three subunits were not different, between the susceptible and resistant mouse strains. CONCLUSIONS: These results show that Pseudomonas infection, by modulating ENaC subunit expression, could influence edema formation and clearance in infected lungs

RNA-seq analysis in plant–fungus interactions

Many fungi are pathogens that infect important food and plantation crops, reducing both yield and quality of food products. Understanding plant–fungus interactions is crucial as knowledge in this area is required to formulate sustainable strategies to improve plant health and crop productivity. High-throughput RNA-sequencing (RNA-seq) enables researchers to gain insights of the mixed and multispecies transcriptomes in plant–fungus interactions. Interpretation of huge data generated by RNA-seq has led to new insights in this area, facilitating a system approach in unraveling interactions between plant hosts and fungal pathogens. In this review, the application and challenges of RNA-seq analysis in plant–fungus interactions will be discussed

Effect of nitrate on acetylene reduction and the activities of some enzymes of nitrogen and carbon metabolism, involved in nitrogen fixation in the root nodules of soybean

Soybean plants (Glycine max (L) Merr) cv Maple arrow were nodulated either by Bradyrhizobium japonicum (USDA 311 b 138 or B japonicum CB 1809 and grown on low-N solution (20 μM nitrate). When the seedlings were 40 days old, treatments with 5 mM nitrate for 1-4 d were used in order to allow effects on acetylene reduction, bacteroid nitrate reductase (EC 1.6.6.1), nodule cytosol nitrate reductase, glutamine synthetase (EC 6.3.1.2) and phosphoenolpyruvate carboxylase (EC 4.1.1.31) to be studied in the absence of nodule senescence. Significant alterations of enzyme activities were only observed in nodules infected by B japonicum USDA 311 b 138. Thus infecting soybean plants with either B japonicum USDA 311 b 138 of B japonicum CB 1809 was a good tool for investigating the effects associated with N2 fixation inhibition by comparing a high nitrate-sensitive and a low nitrate-sensitive symbiosis. Phosphoenolpyruvate carboxylase and acetylene reduction activities were rapidly lowered while the bacteroid inducible nitrate reductase increased. In contrast, the nodule cytosolic glutamine synthetase and nitrate reductase activities slowly increased after the ARA had declined. These data suggest that the nodule cytosol phosphoenolpyruvate carboxylase and the bacteroid nitrogenase are the 2 main regulatory enzymes controlling C and N metabolism respectively, in symbiotic nodules. On the other hand, parallelism of nodule cytosol nitrate reductase and glutamine synthetase suggest that in these soybean nodules, the cytosolic glutamine synthetase was devoted to assimilation of the NH+4 product of nitrate assimilation.Rôle du nitrate sur la réduction de l'acétylène et les activités de quelques enzymes des métabolismes carboné et azoté impliqués dans la fixation de l'azote dans les nodules racinaires de soja. Il est bien connu que l'application de nitrates à des cultures de soja en symbiose avec Bradyrhizobium japonicum altère l'activité nitrogénase responsable de la fixation de l'azote moléculaire, avec vieillissement prématuré des nodosités. La nutrition azotée des plantes passe alors de la symbiose à l'autotrophie. L'objet des recherches décrites dans le présent article est d'étudier les effets des nitrates comparativement sur la nitrogénase (mesurée par l'activité de réduction de l'acétylène ou ARA) et sur 2 enzymes qui lui sont associées dans les premières étapes de l'assimilation de l'azote, la phosphoénolpyruvate carboxylase (EC 4.1.1.31) et la glutamine synthétase (EC 6.3.1.2), toutes 2 localisées dans le cytosol du tissu végétal des nodosités. Les activités de la nitrate réductase des bactéroïdes et de la nitrate réductase (EC 1.6.6.1) du tissu végétal des nodosités sont également mesurées. Des plantes de soja ( Glycine max L Merr) cv Maple arrow sont inoculées soit par Bradyrhizobium japonicum USDA 311 b 138, soit par B japonicum CB 1809. Ces 2 souches ont été choisies car, ayant des sensibilités différentes aux nitrates, elles permettent la comparaison de systèmes symbiotiques de niveaux de résistance distincts. Les plantes inoculées sont cultivées sur solution minérale sans N, mais contenant cependant les traces de nitrate de l'eau (20 μmol·l-1). Le développement des plantes des des nodosités, l'activité fixatrice d'azote, la teneur en hémoglobine sont identiques, dans les 2 types d'association symbiotique (tableau I). Les traitements par le nitrate (5 mmol·l-1) sont appliqués pendant 1-4 j afin de permettre l'étude de leurs effets sur la réduction de l'acétylène, et les activités enzymatiques citées plus haut, indépendamment des phénomènes liés à la sénescence des nodosités. Une partie des nitrates absorbés par les racines pénètre dans les nodosités via la sève du xylème (fig 1). Une diminution rapide et significative de l'ARA n'est observée que dans les nodosités infectées par B japonicum USDA 311 b 138 (fig 2). Ainsi, l'inoculation du soja soit avec B japonicum USDA 311 b 138, soit avec B japonicum CB 1809 est un bon outil pour l'étude des effets associés à l'inhibition de la fixation de N2 avec comparaison de symbioses ayant différents degrés de sensibilité au nitrate. La diminution rapide de l'ARA est accompagnée chez B japonicum USDA 311 b 138 d'une augmentation de l'activité nitrate réductase des bactéroïdes et de l'activité phosphoénolpyruvate carboxylase du cytosol. Au contraire, la glutamine synthétase et la nitrate réductase du tissu végétal des nodosités n'augmentent que très lentement après le déclin de l'activité de réduction de l'acétylène (fig 3). Dans les nodosités inoculées par B japonicum CB 1809, aucune modification d'importance des activités enzymatiques étudiées, y compris l'ARA, ne se remarque (fig 4). Ces données suggèrent que la phosphoénolpyruvate carboxylase du cytosol des nodosités ainsi que la nitrogénase des bactéroïdes sont 2 enzymes majeures de la régulation respectivement du métabolisme du carbone et du métabolisme de l'azote, dans les nodosités en symbiose. Le parallélisme de l'évolution de la glutamine synthétase et de la nitrate réductase cytosoliques suggère que dans les nodosités de soja, le rôle de la glutamine synthétase cytosolique serait essentiellement associé à l'assimilation de NH +4, produit de l'assimilation de NO-3