The goals of our study were to test our hypothesis that many genes would be differentially expressed in response to arsenate stress and to identify genes as putative players in As detoxification using Arabidopsis as a model. In this paper, we investigate the transcriptional responses to As in Arabidopsis thaliana using oligonucleotide microarrays. http://www.selleckchem.com/products/Gefitinib.html Our results demon strate that As stress strongly induces Cu Zn superoxide dismutase activity, but represses the production of Fe SODs. Our microarray data also suggest the involve ment of other antioxidant genes, various transcription fac tors, tonoplast proteins, and proteins associated with cell wall growth. Of particular interest, we report that As stress represses numerous genes induced by Pi starvation.

We discuss the physiological implications of these find ings, and suggest new avenues for research of arsenic metabolism in plants. Results Root growth under As stress Inhibitors,Modulators,Libraries Arsenate exposure resulted in reduced Arabidopsis root growth and branching. Exposure of 50M As resulted in significantly reduced Arabidopsis root growth. In addition Inhibitors,Modulators,Libraries to known relevant physi ological data, the exposure study was used to determine suitable As exposure for the microarray study. We noted no seed germination effects with regard to arsenate treatments, notably at 100M, the arsenate concentration used for transcriptomics experiments. Gene ontology for genes affected by As Forty six genes were induced by As treatment as indicated by microarray analysis. The largest functional categories affected included unknown function, hydrolase, and anti oxidant Inhibitors,Modulators,Libraries activity.

Other functional categories affected by As included genes with transferase, kinase, lyase, trans porter, and binding Inhibitors,Modulators,Libraries activity. Alternatively, 113 genes were repressed by As. with unknown function, hydrolase, and binding activity representing the largest categories. Genes with transporter, kinase, trans ferase, and transcriptional regulator activity Inhibitors,Modulators,Libraries were also repressed by As. Differ entially expressed As induced and repressed genes are listed below and com plete lists of all genes affected by As stress are also included as additional files. Most interestingly, it was discovered that As stress repressed transcription of many genes involved in the phosphate starvation response, and also repressed several transcriptional factors.

Several genes involved in oxidative stress were also highly modulated in response to As. Superoxide dismutases SODs represented the highest ranked of both significantly induced as well as repressed genes in response to As stress, therefore these genes presented logical technical support primary targets for the validation of our microarray data. Results demonstrated 4. 57 fold induction of a chlo roplast Cu Zn SOD, 2. 41 fold induction of a Cu Zn SOD, as well as a 3. 16 fold induction of an SOD copper chaperone. Alternatively, Fe SOD transcripts were downregulated in response to arsenic stress. These find ings were confirmed with quantitative RT PCR.