Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

MMP101

ABSTRACT: Methanococcus maripaludis is a methanogenic archaeon. Within its genome, there are two operons for membrane associated hydrogenases, eha and ehb. To investigate the regulation of ehb on the cell, an S40 mutant was constructed in such a way that a portion of the ehb operon was replaced by pac cassette in the wild type parental strain S2 (done by Whitman's group at the University of Georgia). Four samples of each strain were grown in batch culture. Differences in transcriptional expression between S40 and S2 were measured using cDNA arrays, with flip dye experiments for each biological replicate. 16 replicates were used for the experiment. Four biological replicates of the wild type (S2) and mutant (S40) strains where compared using dye flips. Each slide contained two copies of the array yielding four technical replicates for each biological replicate.

ORGANISM(S): Methanococcus maripaludis

SUBMITTER: John Leigh

PROVIDER: E-GEOD-2745 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Quantitative proteomics of the archaeon Methanococcus maripaludis validated by microarray analysis and real time PCR.

Xia Qiangwei Q Hendrickson Erik L EL Zhang Yi Y Wang Tiansong T Taub Fred F Moore Brian C BC Porat Iris I Whitman William B WB Hackett Murray M Leigh John A JA

Molecular & cellular proteomics : MCP 20060217 5

For the archaeon Methanococcus maripaludis, a fully sequenced and annotated model species of hydrogenotrophic methanogen, we report validation of quantitative protein level expression ratios on a proteome-wide basis. Using an approach based on quantitative multidimensional capillary HPLC and quadrupole ion trap mass spectrometry, coverage of gene expression approached that currently achievable with transcription microarrays. Comprehensive mass spectrometry-based proteomics and spotted cDNA array ...[more]

PMID: 16489187

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Project description:Arabidopsis thaliana plants (ecotype Landsberg erecta) were grown at 20ËC constant temperature, 8 hr/16 hr Light/Dark photoperiod at 50-60% ambient humidity, for 8 to 9 weeks. Short day conditions prevented the onset of flowering and the plants were thus maintained in growth stage 1 (leaf production) with 13 to 15 rosette leaves larger than 1mm (stage 1.13 to 1.14). Diamondback moth (DBM, Plutella xylostella) larvae were maintained on cabbage (Brassica oleracea) plants in a climate-controlled room at 25ÂºC, 12 hr photoperiod with 50%-60% relative humidity. Two days before exposing A. thaliana plants to herbivore treatment, plants were transferred to a climate-controlled room (22ÂºC, 50-60% humidity, 12 hr photoperiod). For insect treatment, seven Diamondback moth (DBM, Plutella xylostella) larvae (third to fifth instars) were placed on a group of four or five plants until time of harvest, for each time point separately. All rosette leaves were harvested at 1h, 4h, 12h, and 24h after onset of continuous herbivory and flash frozen in liquid nitrogen. Control plants were maintained under the same conditions and harvested in parallel. Keywords: time course, stress response, herbivory response For each time point (1h, 4h, 12h, and 24h) two biological replicates (DBM treatment) were performed. Control plants were harvested in parallel. Total RNA from each sample was used for two labelling reactions using dye-flips (Cy5 or Cy3) and labelled cDNA from treatment and control plants were co-hybridized. Thus, for each time-point four replicates were analyzed each comparing treatment with the corresponding control (rep1 and rep2 are dye-flips of biological replicate 1, and rep3 and rep4 are dye-flips of biological replicate 2). For background correction, we defined the mean of the lowest 10% of spot intensities from a particular subgrid as the background for that subgrid. This mean was subtracted from each spot in the subgrid. Signal intensities that did not exceed the background plus 3 standard deviations thereof were defined as not detectable and were excluded from further analyses. We normalized using loess curves thus generating log2 transformed expression ratios comparing DBM treatment with control. These ratios are given in the VALUE columns of each array.

Project description:The fumarate and nitrate reductase regulator protein, FNR, is a global transcription factor that regulates major biochemical changes as Escherichia coli adapts from aerobic to anaerobic growth. The ability of an fnr mutant to grow anaerobically in the presence of trimethylamine-N-oxide (TMAO) as the terminal electron acceptor was exploited in microarray experiments designed to determine a minimum number of Escherichia coli K-12 MG1655 operons that are regulated directly by FNR. In an anaerobic glycerol-TMAO-fumarate medium, the fnr mutant grew as well as the parental strain, enabling us to reveal the response of the E. coli transcriptome to oxygen, nitrate and nitrite in the absence of glucose repression or artefacts due to variations in growth rate. Many of the discrepancies between previous microarray studies of the E. coli FNR regulon were resolved in this study. First data for 43 previously characterised FNR-dependent operons were analysed. The current microarray data confirmed 32 of these 43 assignments, but alone did not confirm FNR-activation of 5 operons (adhE, glpTQ, cydDC, hlyE and arcA), or FNR repression of 6 operons (hemA, narXL, tpx, yeiL, norVW or ubiCA). Thirty-six operons not previously known to be included in the FNR regulon were activated by FNR and a further 26 operons appeared to be repressed. For each of these operons, an excellent match to the consensus FNR-binding site sequence was identified. The FNR regulon therefore minimally includes at least 94, and possibly as many as 105, operons. Many FNR-activated promoters are also regulated by one or both of two nitrate- and nitrite-responsive two-component regulatory systems, NarX-NarL and NarQ-NarP. Comparison of transcripts in the parental strain and a narXL deletion mutant revealed that transcription of 51 operons is activated, directly or indirectly, by NarL in response to nitrate, and a further 41 are repressed. As phosphorylated NarL can bind to the NarP DNA target sequence, the narP gene was also deleted from the narXL mutant to reveal the extent of regulation by phosphorylated NarP. Fourteen promoters were more active in the narP+ strain than in the mutant, and a further 37 were strongly repressed. This is the first report that NarP might function as a global repressor as well as a transcription activator. The data also revealed possible new biochemical defence mechanisms against reactive nitrogen species. Keywords: genetic modification, growth conditions An fnr mutant is either unable to grow anaerobically in the presence of most terminal electron acceptors and a non-fermentable carbon source such as glycerol or lactate, or grows far more slowly than the parental strain. Under such conditions, any differences in the transcriptomes of an fnr mutant and its parental strain would be due to both direct effects of FNR, and to differences in growth rate. As glucose represses expression from some FNR-activated promoters replacement of glucose by a less repressing fermentable carbohydrate would decrease effects due to glucose repression, but to an unknown extent. We therefore exploited the fact that fnr mutants can be grown anaerobically in the presence of the non-fermentable and non-repressing carbon source, glycerol, in the presence of trimethylamine-N-oxide (TMAO) in addition to fumarate as the terminal electron acceptor. Furthermore, the presence of TMAO has a minimal effect on NarX-NarL or NarQ-NarP-dependent induction or repression. Under these conditions, the fnr mutant grows as well as the parental strain and the use of the glycerol-TMAO-fumarate medium enables us to reveal the response of the E. coli transcriptome to nitrate, nitrite and the two-component regulator system, NarX-NarL. In each large set of experiments a common pool of reference RNA isolated from bacteria that had been grown anaerobically, and in which FNR-activated genes were expressed at a significant level. A potential disadvantage of this approach was the risk that some promoters repressed by FNR would be expressed at such a low level that the microarray signals would be too low to yield reliable data. To check for this artefact, further experiments were completed in which the reference RNA was a pool of samples isolated from bacteria in the early exponential phase of aerobic growth. “Reference” RNA was isolated from at least four independent cultures grown to OD 0.5 to 0.6. “Test” RNA was isolated from three independent cultures grown to OD 0.5 to 0.6.

Dataset Information

MMP101

Publications

Quantitative proteomics of the archaeon Methanococcus maripaludis validated by microarray analysis and real time PCR.

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