Inducible and constitutive heat shock gene expression responds to modification of Hsp70 copy number in Drosophila melanogaster but does not compensate for loss of thermotolerance in Hsp70 null flies

<p>Abstract</p> <p>Background</p> <p>The heat shock protein Hsp70 promotes inducible thermotolerance in nearly every organism examined to date. Hsp70 interacts with a network of other stress-response proteins, and dissecting the relative roles of these interactions in causing thermotolerance remains difficult. Here we examine the effect of <it>Hsp70 </it>gene copy number modification on thermotolerance and the expression of multiple stress-response genes in <it>Drosophila melanogaster</it>, to determine which genes may represent mechanisms of stress tolerance independent of Hsp70.</p> <p>Results</p> <p><it>Hsp70 </it>copy number in four strains is positively associated with <it>Hsp70 </it>expression and inducible thermotolerance of severe heat shock. When assayed at carefully chosen temperatures, <it>Hsp70 </it>null flies are almost entirely deficient in thermotolerance. In contrast to expectations, increasing <it>Hsp70 </it>expression levels induced by thermal pretreatment are associated with increasing levels of seven other inducible <it>Hsps </it>across strains. In addition, complete <it>Hsp70 </it>loss causes upregulation of the inducible <it>Hsps </it>and six constitutive stress-response genes following severe heat shocks.</p> <p>Conclusion</p> <p>Modification of <it>Hsp70 </it>copy number quantitatively and qualitatively affects the expression of multiple other stress-response genes. A positive association between absolute expression levels of <it>Hsp70 </it>and other <it>Hsps </it>after thermal pretreatment suggests novel regulatory mechanisms. Severe heat shocks induce both novel gene expression patterns and almost total mortality in the <it>Hsp70 </it>null strain: alteration of gene expression in this strain does not compensate for <it>Hsp70 </it>loss but suggests candidates for overexpression studies.</p

Inducible and constitutive heat shock gene expression responds to modification of copy number in but does not compensate for loss of thermotolerance in null flies-2

<p><b>Copyright information:</b></p><p>Taken from "Inducible and constitutive heat shock gene expression responds to modification of copy number in but does not compensate for loss of thermotolerance in null flies"</p><p>http://www.biomedcentral.com/1741-7007/6/5</p><p>BMC Biology 2008;6():5-5.</p><p>Published online 22 Jan 2008</p><p>PMCID:PMC2257928.</p><p></p>scription of the treatments). LSMs are expressed in reciprocally transformed CT values (1000/cycle number). Symbols are means ± 1 SE; the legend at top of figure indicates gene-symbol pairs. Graphs are organized according to strain (left to right) and timepoint post treatment (top to bottom). Mean fold changes in expression levels of all seven genes after PT and PT+HS39, relative to C, are indicated by the large arrows and numbers; arrows indicate direction of change