Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Transcriptional Analysis of Medicago truncatula and Glycine max Using Tiling Microarrays

ABSTRACT: This SuperSeries is composed of the following subset Series: GSE10055: Transcriptional Analysis of 1M Regions in Medicago truncatula Using Tiling Microarrays GSE10056: Transcriptional Analysis of 1M Regions in Glycine max Using Tiling Microarrays Keywords: tiling array, transcriptional analysis Both the barrel medic and soybean tiling arrays were produced on the Maskless Array Synthesizer platform. Briefly, tiling-paths consisting of 36-mer oligonucleotides offset by five nucleotides were designed to represent both DNA strands of the selected barrel medic and soybean genome sequence. Probes were synthesized at a feature-density of 390,000 probes per array in a âchess boardâ design. Microarray production and storage were carried out. Total RNA and mRNA were sequentially isolated using the RNeasy Plant Mini kit (Qiagen, Valencia, CA) and the Oligotex mRNA kit (Qiagen) according to the manufacturerâs recommendations, respectively. mRNA from different organ types was reverse transcribed using a mixture of oligo(dT)18 and random nonamer primers, during which amino-allyl-modified dUTP (aa-dUTP) was incoporated. The aa-dUTP decorated cDNA was fluorescent labeled by conjugating the monofunctional Cy3 dye (GE Healthcare, Piscataway, NJ) to the amino-allyl functional groups in the cDNA. Two Î¼g dye-labeled targets were used for hybridization.

ORGANISM(S): Glycine max

SUBMITTER: Hang He

PROVIDER: E-GEOD-10151 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Transcriptional analysis of highly syntenic regions between Medicago truncatula and Glycine max using tiling microarrays.

Li Lei L He Hang H Zhang Juan J Wang Xiangfeng X Bai Sulan S Stolc Viktor V Tongprasit Waraporn W Young Nevin D ND Yu Oliver O Deng Xing-Wang XW

Genome biology 20080319 3

<h4>Background</h4>Legumes are the third largest family of flowering plants and are unique among crop species in their ability to fix atmospheric nitrogen. As a result of recent genome sequencing efforts, legumes are now one of a few plant families with extensive genomic and transcriptomic data available in multiple species. The unprecedented complexity and impending completeness of these data create opportunities for new approaches to discovery.<h4>Results</h4>We report here a transcriptional a ...[more]

PMID: 18348734

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Project description:In the study of gene expression regulation in plants, it is often desirable to distinguish transcript pools derived from different alleles present in the same organism. We report here an oligonucleotide tiling microarray designed to specifically target 518 single nucleotide polymorphisms (SNPs) between the two sequenced rice (Oryza sativa) subspecies indica and japonica. The tiling array includes all pairs of 25-mer allele-specific probes interrogating each SNP by placing the polymorphic site at all 25 possible positions within the probe. Hybridization of the tiling array to a titration series in which the japonica- and indica-derived cDNA templates are mixed with altering proportions and development of a novel bioinformatic methodology allowed us to screen for diagnostic probe pairs for each SNP. Our result indicates that 284 (55%) SNPs have at least one diagnostic probe pair suitable for distinguishing and quantifying the relative abundance of allele-specific transcripts. As a proof-of-concept, we analyzed allele-specific expression in reciprocal indica × japonica F1 hybrids and detected imbalanced expression at 95 (33%) and 71 (25%) SNPs, respectively. Comparison results from RNA-sequencing and allele-specific real-time PCR experiment validates the sensitivity and reliability of the tiling array method. Together, our results demonstrate the advantages of the tiling array method in interrogating large numbers of SNPs and for the reliability of the experimental and analytical techniques used for quantifying allele-specific gene expression. For each selected SNP, 25 pairs of 25-mer oligonucleotide probes were designed with one match perfectly to the indica allele and the other the japonica allele within each pair. Among the 25 probe pairs, the polymorphic site was placed at a different position such that all possible 25-mer allele-specific probes spanning the polymorphic site were included. The resultant 25,900 probes were synthesized in triplicate in a single microarray produced on the Maskless Array Synthesizer platform as previously described (Li et al., 2005; 2006). Poly(A+) RNA from japonica, indica and their reciprocal hybrids was reverse transcribed using an oligo(dT)18 primer, during which amino-allyl-modified dUTP (aa-dUTP) was incorporated. The aa-dUTP decorated cDNA was fluorescent labeled by conjugating the monofunctional Cy3 dye (GE Healthcare) to the amino-allyl functional groups in the cDNA. Dye-labeled target was quantified using a spectrophotometer and two μg used for hybridization to each array. In the titration series experiment, the dye-labeled targets from japonica and indica were mixed in known proportions before hybridization.

Project description:CcpA is a global regulator of transcription in Gram-positive bacteria that controls gene expression in response to carbohydrate availability. Using the fructan hydrolase (fruA) gene of S. mutans as a model, we demonstrate that CcpA does indeed play a major role in carbohydrate catabolite repression. Using DNA microarrays, the expression of at least 170 genes differed in CcpA-deficient cells compared to the parental strains when cells are grown in the presence of glucose, but only 90 genes showed altered expression when cells were cultivated in the poorly-repressing substrate galactose. Interestingly, 90 genes were differently expressed in wild-type S. mutans in response to cultivation in glucose versus galactose, but the expression of over 500 genes was altered when growth in glucose and galactose were compared in the CcpA-deficient strain. The results support a major role for CcpA in regulation of gene expression, but reveal that a substantial CcpA-independent network exists in S. mutans to regulate gene expression in response to carbohydrate source. A reference RNA that had been isolated from 2 liters of UA159 cells grown in BHI broth to OD600 = 0.5 was used in every experiment. Our experimental conditions consisted of S. mutans UA159 and TW1 grown in TV supplemented with 0.5% glucose or 0.5% galactose and collected at the mid-exponential phase of growth (OD600 = 0.5). All RNAs were purified as described above and used to generate cDNA according to the protocol provided by TIGR with the following minor modifications. The amount of RNA in each reaction was increased to 10 ug and the molar ratio of dTTP:aa-dUTP was increased to 1:2. SuperscriptIII Reverse transcriptase (Invitrogen, Gaithersburg, MD) was used to increase cDNA yields. Purified cDNAs were coupled with indocarbocyanine (Cy3)-dUTP, while reference cDNA was coupled with indodicarbocyanine (Cy5)-dUTP (Amersham Biosciences, Piscataway, NJ). Four individual Cy3-labeled cDNA samples originating from four different cultures of UA159 or TW1, grown in each experimental condition, were hybridized to the arrays along with Cy5-labeled reference cDNA, generating a total of 16 slides. Hybridizations were carried out in a Maui 4-chamber hybridization system (BioMicro Systems, Salt Lake City, Utah) for 17 h at 42ºC. The slides were then washed according to TIGR protocols and scanned using a GenePix Scanner (Axon Instruments Inc., Union City, CA). After the slides were scanned, single-channel images were loaded into TIGR Spotfinder software and overlayed. A spot grid was created according to TIGR specifications and manually adjusted to fit all spots within the grid, then the intensity values of each spot were measured. Data was normalized using TIGR Microarray data analysis software (MIDAS), by using LOWESS and Iterative Log Mean Centering with default settings, followed by In-Slide Replicate Analysis. Statistical analysis was carried out using BRB Array Tools with a cutoff P value of 0.001 for class prediction and class comparison.

Project description:A genome-wide location analysis by ChIP on chip of the gene occupancy by Sub1 was undertaken to define the gene targets of Sub1 in vivo. Chromatin immunoprecipitation (ChIP) assays were performed on epitope-tagged Sub1-3HA cross-linked chromatin from exponentially growing cells. Immunopurified DNA and DNA from whole-cell extracts were fluorescently labelled and competitively hybridized to DNA microarrays harbouring ORFs and intergenic regions. The ratio of fluorescence intensities at each site in the microarray provided a measure of the extent of Sub1 binding to a specific genomic locus. Data from three independent experiments were compiled. Many loci were found to be significantly enriched in active growth conditions where Sub1 is not essential for cell viability. Approximately one-fourth of the enriched loci were located within ORF and the others corresponded to intergenic regions and to genes encoding non-translated RNAs. The ACT1, PMA1, PYK1, ADH1 and snoRNA genes previously identified as DNA targets of Sub1 were indeed enriched in our data. Sub1 was also preferentially bound to a subset of Pol II-transcribed genes encoding constituents of the cell wall, the nucleosome and the ribosome. Remarkably, these Pol II genes represented only two-third of the enriched loci. The other ones corresponded to Pol III-transcribed genes present on the arrays or to the intergenic regions and ORFs adjacent to these genes, suggesting the association of Sub1 to all Pol III-transcribed genes in conditions of active growth. The arrays used had a poor coverage of the rDNA gene locus. Nevertheless, we found a significant enrichment of the different loci corresponding to that region suggesting that Sub1 associates at many locations throughout the rDNA gene. Altogether, the results suggested that Sub1 could be a regulator of all three transcription systems. Keywords: ChIP-Chip Chromatin immunoprecipitation Chromatin immunoprecipitations were performed essentially as described by Ren et al. (2000) with some modifications described below. Briefly, overnight yeast cultures were used to inoculate fresh YPD medium at 0.1 OD600. The cells were grown in 100 mL of YPD to 1 OD600 and fixed with formaldehyde at a final concentration of 1% for 15 min at room temperature. Fixation was stopped by the addition of glycine (final concentration 340 mM) and incubation for 5 min. The fixed cells were harvested by centrifugation and washed twice with cold TBS. The cell pellets were frozen and stored at –80°C for further use. The cell pellets were thawed, resuspended in 700 µL of lysis buffer (50 mM HEPES-KOH pH 7.5, 140 mM NaCl, 1 mM EDTA, 1% Triton X-100, 0.1% Na-deoxycholate, 1 mM PMSF, O Complete protease inhibitor (Roche)) and transferred to 1.5 mL Eppendorf tubes. 0.5 mL glass beads (425-600 µm, Sigma) were then added to each tube, and the yeast cells were lysed at 4°C for 2 hours using an Eppendorf Thermomixer Comfort at 1400 rpm. Each tube was pierced at the bottom and the cell lysate was collected by centrifugation in a fresh tube. The lysate was then sonicated 4 times for 10 s with 20 s cooling on ice between each sonication. The power of the Vibra Cell™ sonicator (Sonics & Materials Inc., Danbury, Connecticut, USA) was set to 4 with 60% duty cycle. Sonication resulted in chromatin fragments of 0.25–1 kb in size with a mean size of 600 base pairs as determined by gel electrophoresis. After 5 min of centrifugation in 1.5 mL Eppendorf tubes at 15 000 rpm, the supernatant (named whole cell extract, WCE) was transferred to another tube on ice. The preparation of magnetic beads, immunoprecipitation (with anti-HA 12CA5 or anti-myc 9E10), elution from beads and reversal of crosslinking, DNA precipitation, DNA blunting and ligation of blunted DNA to linkers were done exactly as described in Ren et al. (2000). Construction of yeast microarrays The S. cerevisiae ORF and intergenic regions were amplified from S288C genomic DNA with oligonucleotides from ResGen. The primers allow the amplification of the sequence located on either side of elements such as open reading frames, tRNAs, small nuclear RNAs, Ty elements, solo δ, etc. A complete description of the primers can be obtained on the web site (ftp://ftp.resgen.com/pub/genepairs/yeast_intergenic). The PCR products were purified by ethanol precipitation and their size and concentration were measured by agarose gel electrophoresis. 95 % of the regions were correctly amplified (as evidenced by gel electrophoresis) and purified at a mean plate concentration of 70 ng/µL. The purified DNAs were spotted onto amino-silane coated glass slides (GAPS II, Corning) using an automated arrayer (MicroGrid II, BioRobotics) with a spotting success percentage higher than 96 %. The final success rate is 93-94 %. LM-PCR, probe labeling and hybridization Ligation-mediated PCR was done as described by Ren et al. (2000) except that amino-allyl conjugated dUTP (150 µM final) was used instead of Cy3-dUTP or Cy5-dUTP and only 30 cycles of PCR were performed. After PCR amplification, 5 μl of the reaction mixtures was run on 1.5% agarose gel to measure the amount of amplified DNA. The PCR product size ranged from 200 to 1000 bp with an average size of 300 bp. The PCR products were purified using a Microcon YM-30 filter (Amicon/Millipore). Amino-allyl modified DNA was recovered with 20 µL of H2O and the DNA was lyophilized. The DNA pellet was resuspended in 9 µL of 100 mM sodium bicarbonate, pH 9.0. This sample DNA was used to dissolve a dry pellet of monofunctional NHS-ester Cy3 or Cy5 (1/16e of the quantity delivered from the mono-reactive dye pack PA23001 or PA25001 respectively from Amersham) and the mixture was incubated for 1 hour at room temperature in the dark. The coupling reaction of the Cy dyes to the amino-allyl dUTP was stopped by quenching with the addition of 4.5 µL of 4M hydroxylamine (Sigma) and the solution was further incubated for 15 min in the dark. Cy3-immunoprecipitated DNA and Cy5-WCE control DNA were mixed and unincorporated/quenched Cy dyes were removed using a Microcon YM-30 filter (Amicon/Millipore). DNA was recovered with 60 µL of TE and ethanol precipitated. Prehybridization and hybridization conditions were those described on P. Brown's web site (http://brownlab.stanford.edu/protocols.html) with few minor modifications. The labeled precipitated DNA samples were recovered in hybridization buffer (50% formamide, 5X Denhardt’s, 0.5% SDS, 7X SSPE, 10 µg herring sperm DNA) and hybridized to the DNA microarray in a Corning slide chamber at 42°C overnight. Arrays were washed at room temperature once with 0.1X SSC + 0.1% SDS, twice with 0.1X SSC, then dried by centrifugation. Data analysis Hybridized arrays were scanned using a GenePix 4000A scanner (Axon Instruments, Inc.) and fluorescence ratio measurements were determined with the GenePix Pro 6.0 software (Axon Instruments, Inc.). Array analyses were undertaken using the Limma package (Smyth, 2005) from the R/Bioconductor software (R-Development-Core-Team, 2007). Data from three independent experiments were compiled. ChIP-chip spot intensities have been normalized using the weighted median as implemented in the normalizeWithinArrays function of the Limma package. Normalized measures served to compute the log2-ratio for each probe. To exhibit enriched probes, we have used a moderated t-test. The moderated t test applied here was based on an empirical Bayes analysis and was equivalent to shrinkage (or expansion) of the estimated sample variances towards a pooled estimate, resulting in a more stable inference, but we have considered a one-sided alternative hypothesis, since we expect higher intensity levels in the IP-enriched hybridizations than in the negative control hybridizations.

Dataset Information

Transcriptional Analysis of Medicago truncatula and Glycine max Using Tiling Microarrays

Publications

Transcriptional analysis of highly syntenic regions between Medicago truncatula and Glycine max using tiling microarrays.

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