Project description:Antibiotic resistance is currently considered as a global threat to public health. It was shown that adaptive resistance mutation and acquisition of resistance genes by horizontal gene transfer are facilitated by RecA-dependent SOS response during antibiotic treatment. In this study, we performed high-throughput determination of minimal inhibitory concentrations (MICs) of 214 chemicals including not only various kinds of antibiotics but also toxic chemicals of unknown drug action in Escherichia coli wild-type MDS42 strain and the ΔrecA mutant strain. The ΔrecA mutant showed increased sensitivity to DNA-damaging agents, DNA replication inhibitors, and chromate stress. The ΔrecA mutant also showed increased sensitivity to chemicals other than DNA-damaging agents such as S-(2-aminoethyl)- l-cysteine, l-histidine, ruthenium red, D-penicillamine, carbonyl cyanide 3-chlorophenylhydrazone (CCCP), cerulenin, and l-cysteine. Microarray analysis showed that expressions of glnK, nac, and glnLG encoding nitrogen assimilation regulators together with amtB encoding ammonium transporter decreased in the ΔrecA mutant strain. These results suggest that ΔrecA mutation affect not only SOS response but also nitrogen assimilation.
Project description:Comparative-genomic studies have reported widespread variation in levels of gene expression within and between species. In the vast majority of cases, the phenotypic and evolutionary relevance of regulatory change is unknown. We haveu sed a wild Malaysian population of S. cerevisiae as a testbed in the search to identify organismal correlates of regulatory variation. Malaysian yeast, when cultured in standard medium, activated regulatory programs that protect cells from the toxic effects of high iron.
Project description:Comparative-genomic studies have reported widespread variation in levels of gene expression within and between species. In the vast majority of cases, the phenotypic and evolutionary relevance of regulatory change is unknown. We haveu sed a wild Malaysian population of S. cerevisiae as a testbed in the search to identify organismal correlates of regulatory variation. Malaysian yeast, when cultured in standard medium, activated regulatory programs that protect cells from the toxic effects of high iron. Analysis of differential gene expression between three Malaysian and two Wine/European isolates and allele-specific expression within three Malaysian x Wine/European hybrids.
Project description:Long-term laboratory evolution experiments provide a controlled record of evolutionary dynamics and metabolic change in microorganisms. Nevertheless, the correspondence between genetic mutation and phenotypic adaptation remains elusive, partly because of the overwhelming number of genetic changes that accrue after tens-of-thousands of generations. Using a coarse-grained characterization of bacterial physiology applied to Lenski's laboratory-evolved strains of Escherichia coli, we identify an intermediate measure between genotype and phenotype that provides insight into the dynamics of adaptation.
Project description:Toxic chemical contaminants have variety of detrimental effects on various species and the impact of pollutants on ecosystems has become an urgent issue. However, very limited species have been examined to date and those studies are mainly limited to vertebrates. In this study, we aimed to establish an ecotoxicogenomic bases for Daphnia magna. Based on a daphnia EST database, we made oligonucleotide-based DNA microarray that has high reproducibility. The DNA microarray was applied to evaluate gene expression profiles of daphnid exposed to chemicals. Characteristic gene expression patterns depending on chemicals indicate that the Daphnia microarray can be used for mechanistic understanding of chemical toxicity. Although acute toxicity test or reproductive toxicity test can provide hazardous concentrations of chemicals, they give no information about mode of action. Our study can be a breakthrough for the evaluation of chemical toxicity on environmental organisms. Keywords: Chemical response
Project description:Several metals are essential nutrients for plants but metals are toxic in excess, deleteriously affecting crop yield and quality. Various kinds of genes involved in metal homeostasis have been investigated in detail over the past few decades and the mechanisms of how metals are absorbed from soil and distributed in plants have been elucidated. However, numerous genes related to metal homeostasis remain to be investigated and a comprehensive analysis of the expressions of these genes is required. In the present study, we investigated the spatial gene expression profile of iron (Fe)-deficient and cadmium (Cd)-stressed rice by a combination of laser capture microdissection and microarray analysis.
Project description:Perform microarray study to select sensitive genes for toxicology analysis on hESC validation system. 10 different toxic chemicals at 48h and 2 controls at 0h and 48h are used
Project description:Epigenetic mechanisms can be influenced by environmental cues and thus evoke phenotypic variation. This plasticity can be advantageous for adaption, but also detrimental if not under tight control. Although having attracted considerable interest, it remains largely unknown if and how environmental cues such as temperature trigger epigenetic alterations. Using fission yeast, we demonstrate that environmentally induced discontinuous phenotypic variation is buffered by a negative feedback loop that involves the RNase Dicer and the protein disaggregase Hsp104. In the absence of Hsp104, Dicer accumulates in cytoplasmic inclusions and heterochromatin becomes unstable at elevated temperatures, an epigenetic state that is inherited for many generations after the heat stress. Dicer instead averts the toxic aggregation of a prionogenic protein. Our results highlight the importance of feedback regulation in building epigenetic memory and uncover Hsp104 and Dicer as homeostatic controllers that buffer environmentally induced stochastic epigenetic variation and toxic aggregation of prionogenic proteins. Various strains grown at 30°C or 37°C