Unknown,Transcriptomics,Genomics,Proteomics

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GAP_Culture_conditions

ABSTRACT: Gene expression analysis of A. parasiticus grown under conditions conducive and nonconductive for aflatoxin production was evaluated using glass slide microarrays containing 765 ESTs. Aflatoxins (AF) produced by Aspergillus flavus and A. parasiticus are responsible for approximately $270M in losses annually in the corn, peanut, cotton, and tree nut industries of the United States. In an attempt to develop effective control procedures, research has focused on elucidating the pathway of aflatoxin biosynthesis with the goal of identifying potential targets for intervention. Research to date points to the involvement of complex and likely overlapping regulatory circuits. To better understand the regulation by nutritional and environmental factors, a targeted cDNA microarray consisting of genes associated with AF production was employed to investigate the influence of nitrogen source, carbon source, temperature, and pH on AF production. For each nutritional or environmental parameter examined, a condition conducive for aflatoxin production was compared with a condition that was non-conducive. Three replicate cultures for each condition were grown. Cultures were grown for 24 hours and harvested. AF production for each culture was quantified and tissues were stored separately at -80C. For array hybridization, tissue samples for each condition were pooled and RNA extracted using Trizol reagent. Keywords = aspergillus Keywords = aflatoxin Keywords = regulation Keywords = secondary metabolism

ORGANISM(S): Aspergillus flavus

SUBMITTER: Michael Price

PROVIDER: E-GEOD-1649 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Aflatoxin conducive and non-conducive growth conditions reveal new gene associations with aflatoxin production.

Price Michael S MS Conners Shannon B SB Tachdjian Sabrina S Kelly Robert M RM Payne Gary A GA

Fungal genetics and biology : FG & B 20050601 6

Research on aflatoxin (AF) production has traditionally focused on defining the AF biosynthetic pathway with the goal of identifying potential targets for intervention. To understand the effect of nitrogen source, carbon source, temperature, and pH on the regulation of AF biosynthesis, a targeted cDNA microarray consisting of genes associated with AF production over time was employed. Expression profiles for genes involved in AF biosynthesis grouped into five clades. A putative regulon was ident ...[more]

PMID: 15878831

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Project description:Aflatoxins are carcinogenic fungal secondary metabolites. Levels of aflatoxins in agricultural commodities are stringently regulated by many countries. A cluster of genes is responsible for aflatoxin biosynthesis by Aspergillus flavus and other closely related species. Expression of the clustered aflatoxin genes is governed by a complex network of regulatory mechanisms. To better understand the molecular events that are associated with aflatoxin production, transcription profiling by microarray analyses which compared three independent aflatoxigenic A. flavus strains to individual isogenic progenies that no longer produced aflatoxins after serial transfers was carried out. Twenty-two significantly differentially expressed features were identified. After physical mapping using the A. oryzae genome sequence as the reference, the number of unique genes was reduced to 16. Compared to the parental strains, changes in the aflatoxin gene expression levels in the progenies were not significant, which suggests that the inability to produce aflatoxins is not caused by decreased expression. The only gene showing higher expression levels in the progenies is homologous to glutathione S-transferease genes. Overexpression of this gene, named hcc, at six- to nine-fold in an aflatoxigenic A. flavus did not cause discernible changes in colony morphology or aflatoxin production. Loss of aflatoxin production after serial transfers may not result from a single event but caused by multiple factors. Keywords: Compartiave hybridization toxigenic and atoxigenic lines of Aspergillus Aspergillus flavus NRRL 29459, NRRL 29474, and NRRL 29490 are aflatoxigenic strains originated from soil collection in a peanut field (Terrell Co., Georgia, USA). Strains 459B-20-2, 474A-20, and 499A-20 were nonaflatoxigenic isolates obtained after 20 serial transfers of the parental strains on potato dextrose agar slants (Horn and Dorner 2002). Comparsions in each experiment consisted of one aflatoxigenic parental strain and one nonaflatoxigenic progeny, compared after 48- or 72-hr growth. Each comparison was repeated with duplicate dye-flip.

Project description:Background. Most methods for constructing aneuploid yeast strains that have gained a specific chromosome rely on spontaneous failures of cell division fidelity. In Saccharomyces cerevisiae, extra chromosomes can be obtained when errors in meiosis or mitosis lead to nondisjunction, or when nuclear breakdown occurs in heterokaryons. We describe a strategy for constructing N+1 disomes that does not require such spontaneous failures. The method combines two well-characterized genetic tools: a conditional centromere that transiently blocks disjunction of one specific chromosome, and a duplication marker assay that identifies disomes among daughter cells. To test the strategy, we targeted chromosomes III, IV, and VI for duplication. Results. The centromere of each target chromosome was replaced by a conditional centromere that can be blocked by growth in galactose, and ura3::HIS3, a duplication marker. Transient exposure to galactose induced the appearance of colonies carrying duplicated markers for chromosomes III or IV, but not VI. Microarray-based comparative genomic hybridization (CGH) confirmed that disomic strains carrying extra chromosome III or IV were generated. Chromosome VI contains several genes known to be deleterious when overexpressed, including the beta-tubulin gene TUB2. To test whether a tubulin stoichiometry imbalance prevents viability in cells carrying an extra chromosome VI, we supplied the parent strain with extra copies of the alpha-tubulin gene TUB1, then induced nondisjunction. Galactose-dependent chromosome VI disomes were produced, as revealed by CGH. Some chromosome VI disomes also carried extra, unselected copies of additional chromosomes. Conclusions. This method causes efficient nondisjunction of a targeted chromosome and allows resulting disomic cells to be identified and maintained. We used the method to test the role of tubulin imbalance in the apparent lethality of disomic chromosome VI. Our results indicate that a tubulin imbalance is necessary for disomic VI lethality, but it may not be the only dosage-dependent effect. Keywords: comparative genomic hybridization, CGH Candidate disomes (Ura+His+) were compared to their euploid parents by CGH. 27 candidate strains were examined with 27 arrays. 4 candidates targeted chromosome III (3 induced, 1 spontaneous), 14 candidates targeted chromosome IV (8 induced, 6 spontaneous), and 9 candidates targeted chromosome VI (all induced).

Project description:The goal of this experiment was to identify gene expression changes that are common in different heart failure (HF) types or specific to an etiology of HF. HF groups studied include doxorubicin induced cardiomyopathy, familial dilated cardiomyopathy, hypertrophic cardiomyopathy, idiopathic dilated cardiomyopathy, ischemic heart disease, peripartum cardiomyopathy, and viral induced cardiomyopathy. Non-diseased left ventricles (LV) were obtained from donor hearts not used for transplantation (these were considered to be unsuitable for transplantation for a variety of reasons including the lack of a tissue-compatible recipient). Failing LV were obtained from patients undergoing heart transplantation. Transmural sections of LV anterior free wall were trimmed of fat, dissected into 1-1.5 gm pieces, and immediately frozen in the operating theater. 100-200 mg of frozen transmural LV was ground to a fine powder in liquid nitrogen using a mortar and pestle. Then total RNA was isolated by a method described by Wei and Khan (A Molecular Cloning Manual). The purity of the RNA extract was assessed by measuring the absorbance at 260 nm and 280 nm. Its quantity and integrity was then examined using RNA Nano Chips on a 2100 Bioanalyzer (Agilent Technologies, Palo Alto, CA, USA). 10 ?g of RNA extracts and a universal human reference RNA (Stratagene, La Jolla, CA, USA) were reverse transcribed with Cy3-dUTP and Cy5-dUTP, respectively, to produce labeled cDNA probes using Thermoscript reverse transcriptase according Hwang JJ et. al. (Physiological Genomics 10: 31-44, 2002). Raw scanned images were processed using ScanAlyze version 2.50 (Michael Eisen, Stanford University, CA, USA). Cy3 and Cy5 scans were superimposed, local backgrounds were subtracted, and the fluorescence intensities of each spot were quantified. All further analyses of CardioChips were done using GeneSpring version 6.1 (Silicon Genetics, Redwood City, CA, USA). The data from each array was normalized first to the reference RNA and then a LOWESS curve was fit to the log-intensity versus log-ratio plot for each array and for each gene across all experiments. 40.0% of the data was used to calculate the LOWESS fit at each point. Differentially expressed genes in each HF group compared to donor hearts were identified by a one-way ANOVA test (P <0.05) with the benjamini and hochberg multiple testing corrections and we selected those genes with an average difference greater than 1.5 fold. A hierarchical clustering analysis was performed using pearson correlation with the separation ratio of 1.0 and minimum distance of 0.001 as similarity measure. Using a cardiovascular-specific gene array (CardioChip) of 42 heart failure (HF) patients from a wide range of etiology groups and 8 non-failing donors, we have identified down-regulation of LIM domain protein which may be an important pathway for the clinical progression of HF. We identified six genes, encoding LIM domain and Homer proteins, that are down-regulated in terminally failing hearts. The LIM and cysteine rich domain 1 (LMCD1) gene, in particular, was significantly down-regulated in all HF samples. This novel finding suggests that the LMCD 1 is a universal biomarker for end-stage HF. Other LIM domain genes were also down-regulated but only in non-familial dilated forms of cardiomyopathy. This is probably due to the fact that down-regulation of LIM protein expression may disrupt the cytoskeletal architecture, leading to dilated cardiomyopathy. In addition to identifying the LIM domain genes as possible regulatory genes involved in HF, we also demonstrated that the gene expression profile was able to classify multiple HF patients groups. This paper is the first to examine viral-induced cardiomyopathy, doxorubicin toxicity cardiomyopathy and perimartum cardiomyopathy and to perform the clustering analysis of those HF types providing new insights into human HF.

Dataset Information

GAP_Culture_conditions

Publications

Aflatoxin conducive and non-conducive growth conditions reveal new gene associations with aflatoxin production.

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