Deep transcriptome-sequencing and proteome analysis of the hydrothermal vent annelid <it>Alvinella pompejana</it> identifies the CvP-bias as a robust measure of eukaryotic thermostability

<p>Abstract</p> <p>Background</p> <p><it>Alvinella pompejana</it> is an annelid worm that inhabits deep-sea hydrothermal vent sites in the Pacific Ocean. Living at a depth of approximately 2500 meters, these worms experience extreme environmental conditions, including high temperature and pressure as well as high levels of sulfide and heavy metals. <it>A. pompejana</it> is one of the most thermotolerant metazoans, making this animal a subject of great interest for studies of eukaryotic thermoadaptation.</p> <p>Results</p> <p>In order to complement existing EST resources we performed deep sequencing of the <it>A. pompejana</it> transcriptome. We identified several thousand novel protein-coding transcripts, nearly doubling the sequence data for this annelid. We then performed an extensive survey of previously established prokaryotic thermoadaptation measures to search for global signals of thermoadaptation in <it>A. pompejana</it> in comparison with mesophilic eukaryotes. In an orthologous set of 457 proteins, we found that the best indicator of thermoadaptation was the difference in frequency of charged versus polar residues (CvP-bias), which was highest in <it>A. pompejana</it>. CvP-bias robustly distinguished prokaryotic thermophiles from prokaryotic mesophiles, as well as the thermophilic fungus <it>Chaetomium thermophilum</it> from mesophilic eukaryotes. Experimental values for thermophilic proteins supported higher CvP-bias as a measure of thermal stability when compared to their mesophilic orthologs. Proteome-wide mean CvP-bias also correlated with the body temperatures of homeothermic birds and mammals.</p> <p>Conclusions</p> <p>Our work extends the transcriptome resources for <it>A. pompejana</it> and identifies the CvP-bias as a robust and widely applicable measure of eukaryotic thermoadaptation.</p> <p>Reviewer</p> <p>This article was reviewed by Sándor Pongor, L. Aravind and Anthony M. Poole.</p