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Affy_root-dvt-nitrogen_medicago: Genetic determinism of root development in Medicago truncatula

ABSTRACT: affy_root-dvt-nitrogen_medicago. The biological question is the study of root development adaptation to external nitrogen availability. One of the typical responses to low N provision consists of an increased root branching which promotes soil exploration. In order to differentiate between genes specifically involved in nitrate response and genes of root development, we had performed experiments on both a wild type and a mutant affected in root architecture, both supplied with two different levels of nitrate. Global gene expression profiling of root cells using microarray analysis will be conducted to identify genes expressed during root branching. First, analysing the differential gene expression between the wild type and the mutant both at low and high level of nitrate, we will identify genes of root development but also genes specifically involved in nitrate response. Then, additional comparisons will concern the modifications of wild type and mutant gene expression between the two levels of nitrate. These genes will be compared to those found to be expressed in the wild type roots under submitted to various nitrogen sources (Ruffel et al., 2008). All together these results will allow us to determine which genes, among the firstly underlined, are specifically involved in root development. The kinetics of expression in different tissues of the most relevant of these genes will be further analysed by qRT-PCR. Three successive experiments in growth chamber were performed on two different genotypes of Medicago truncatula. Each experiment constituted a biological replicate. For each of them, after 4 days of seed cold-treatment followed by 4 days of germination, individual plantlets were transferred onto hydroponic culture tanks containing vigorously aerated nutrient solution. Each tank contained 6 plantlets of J5 and 6 plantlets of the mutant. On one shelf of the growth chamber, nutrient solution in the tanks was supplemented by 1mM of KNO3; on the other shelf, the level of KNO3 in the solution was of 10mM. Nutrient solution was renewed every week. Roots of the two genotypes were harvested separately but at the same time, 10 days after the plantlets transfer onto hydroponic culture tanks. Keywords: dose response, wt vs mutant comparison

ORGANISM(S): Medicago sativa Sinorhizobium meliloti Medicago truncatula

PROVIDER: GSE18318 | GEO | 2010/01/29

SECONDARY ACCESSION(S): PRJNA117969

REPOSITORIES: GEO

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Project description:affy_root-dvt-nitrogen_medicago. The biological question is the study of root development adaptation to external nitrogen availability. One of the typical responses to low N provision consists of an increased root branching which promotes soil exploration. In order to differentiate between genes specifically involved in nitrate response and genes of root development, we had performed experiments on both a wild type and a mutant affected in root architecture, both supplied with two different levels of nitrate. Global gene expression profiling of root cells using microarray analysis will be conducted to identify genes expressed during root branching. First, analysing the differential gene expression between the wild type and the mutant both at low and high level of nitrate, we will identify genes of root development but also genes specifically involved in nitrate response. Then, additional comparisons will concern the modifications of wild type and mutant gene expression between the two levels of nitrate. These genes will be compared to those found to be expressed in the wild type roots under submitted to various nitrogen sources (Ruffel et al., 2008). All together these results will allow us to determine which genes, among the firstly underlined, are specifically involved in root development. The kinetics of expression in different tissues of the most relevant of these genes will be further analysed by qRT-PCR. Three successive experiments in growth chamber were performed on two different genotypes of Medicago truncatula. Each experiment constituted a biological replicate. For each of them, after 4 days of seed cold-treatment followed by 4 days of germination, individual plantlets were transferred onto hydroponic culture tanks containing vigorously aerated nutrient solution. Each tank contained 6 plantlets of J5 and 6 plantlets of the mutant. On one shelf of the growth chamber, nutrient solution in the tanks was supplemented by 1mM of KNO3; on the other shelf, the level of KNO3 in the solution was of 10mM. Nutrient solution was renewed every week. Roots of the two genotypes were harvested separately but at the same time, 10 days after the plantlets transfer onto hydroponic culture tanks. Experiment Overall Design: 12 arrays - Medicago. Experiment Overall Design: WT and mutant (tr185) under 1mM or 10mM KNO3. Three biological replicates each genotype/condition.

Project description:The transition metal tungsten (W) finds increasing application in military, aviation and household appliance industry, opening new paths for the heavy metal into the environment. Since tungsten shares certain chemical properties with the essential plant micro nutrient molybdenum, it is proposed to inhibit enzymatic activity of molybdoenzymes by replacing the Mo-ion bound to the co-factor. However, recent studies suggest the inhibition of enzymatic activity might not be the only effect W has on plants and that, much like other heavy metals, tungsten exerts toxicity on its own. Still, our understanding of the mechanisms behind the apparent phytotoxicity remains limited.This study investigates the effects of W on growth, nutrient levels (ionome, ICP-MS), starch levels and nitrogen nutrition (IRMS, enzyme activity assays) as well as root and nodule proteome (LC-MS/MS) of Glycine max cv. Primus. Plants were inoculated with Bradyrhizobium japonicum and grown in a semi hydroponic set up using three different tungsten concentrations (zero, 0.1 mM and 0.5 mM). To identify possible benefits of a functional bacterial symbiosis on W induced stress response, two different environmental growth conditions, one with suppressed N-fixation, supplied with Nitrate (10 mM KNO3) and one solely relying on symbiotic N-fixation (zero KNO3), were applied. Glycine max was able to take up considerable amounts of W (703 ± 136 mg kg-1). However, high W resulted in a strong reduction of shoot biomass of both N regimes and of root biomass (N fed only). Irrespective of N regime, NR activity and total N decreased with increasing W concentrations. Similarly, nitrogenase precursor levels as well as N2-fixation, nodule fixation activity (mg N g-1 nodule dry weight) and nodulation were reduced, indicating that nitrogenase synthesis and activity were negatively affected by W stress. However, along a N fix nodule specific induction of the secondary and phytohormone metabolism, it appears that N2 fixation of remaining nodules was not as severely affected by increasing levels of tungsten than nitrate reduction. Besides N metabolism, plants exhibited an imbalance in nutrient and a failure of carbon metabolic pathways accompanied by an accumulation of starch at high tungsten concentrations, independent of N-regime. Proteomic data demonstrated that the response to high W concentrations is independent of nodule functionality and dominated by several peroxidases and other general stress related proteins. Based on an evaluation of several W responsive proteotypic peptides, we identified a set of protein markers of W stress and possible targets for improved stress tolerance.

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Affy_root-dvt-nitrogen_medicago: Genetic determinism of root development in Medicago truncatula

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