Expression of the pair-rule gene homologs runt, Pax3/7, even-skipped-1 and even-skipped-2 during larval and juvenile development of the polychaete annelid Capitella teleta does not support a role in segmentation

<p>Abstract</p> <p>Background</p> <p>Annelids and arthropods each possess a segmented body. Whether this similarity represents an evolutionary convergence or inheritance from a common segmented ancestor is the subject of ongoing investigation.</p> <p>Methods</p> <p>To investigate whether annelids and arthropods share molecular components that control segmentation, we isolated orthologs of the <it>Drosophila melanogaster </it>pair-rule genes, <it>runt</it>, <it>paired </it>(<it>Pax3/7</it>) and <it>eve</it>, from the polychaete annelid <it>Capitella teleta </it>and used whole mount <it>in situ </it>hybridization to characterize their expression patterns.</p> <p>Results</p> <p>When segments first appear, expression of the single <it>C. teleta runt </it>ortholog is only detected in the brain. Later, <it>Ct-runt </it>is expressed in the ventral nerve cord, foregut and hindgut. Analysis of <it>Pax </it>genes in the <it>C. teleta </it>genome reveals the presence of a single <it>Pax3/7 </it>ortholog. <it>Ct-Pax3/7 </it>is initially detected in the mid-body prior to segmentation, but is restricted to two longitudinal bands in the ventral ectoderm. Each of the two <it>C. teleta eve </it>orthologs has a unique and complex expression pattern, although there is partial overlap in several tissues. Prior to and during segment formation, <it>Ct-eve1 </it>and <it>Ct-eve2 </it>are both expressed in the bilaterial pair of mesoteloblasts, while <it>Ct-eve1 </it>is expressed in the descendant mesodermal band cells. At later stages, <it>Ct-eve2 </it>is expressed in the central and peripheral nervous system, and in mesoderm along the dorsal midline. In late stage larvae and adults, <it>Ct-eve1 </it>and <it>Ct-eve2 </it>are expressed in the posterior growth zone.</p> <p>Conclusions</p> <p><it>C. teleta eve, Pax3/7 </it>and <it>runt </it>homologs all have distinct expression patterns and share expression domains with homologs from other bilaterians. None of the pair-rule orthologs examined in <it>C. teleta </it>exhibit segmental or pair-rule stripes of expression in the ectoderm or mesoderm, consistent with an independent origin of segmentation between annelids and arthropods.</p

Spatial extent and historical context of North Sea oxygen depletion in August 2010

Prompted by recent observations of seasonal low dissolved oxygen from two moorings in the North Sea, a hydrographic survey in August 2010 mapped the spatial extent of summer oxygen depletion. Typical near-bed dissolved oxygen saturations in the stratified regions of the North Sea were 75–80 % while the well-mixed regions of the southern North Sea reached 90 %. Two regions of strong thermal stratification, the area between the Dooley and Central North Sea Currents and the area known as the Oyster Grounds, had oxygen saturations as low as 65 and 70 % (200 and 180 µmol dm-3) respectively. Low dissolved oxygen was apparent in regions characterised by low advection, high stratification, elevated organic matter production from the spring bloom and a deep chlorophyll maximum. Historical data over the last century from the International Council for the Exploration of the Sea oceanographic database highlight an increase in seasonal oxygen depletion and a warming over the past 20 years. The 2010 survey is consistent with, and reinforces, the signal of recent depleted oxygen at key locations seen in the (albeit sparse) historical data

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Relevance of Photolysis Frequencies Calculation Aspects to the Ozone Concentration Simulation

For the simulation of photochemically created pollutants like ozone it is essential to correctly consider reaction rates induced by short-wave radiation. In atmospheric chemistry transport models this is achieved by the use of either off- or online calculated photolysis frequencies. In this study the effect of different input parameters of a radiation model on the calculated photolysis frequencies have been investigated. In the second step an atmospheric chemistry transport model was used to assess the impact of changed photolysis frequencies on the simulation of ozone concentrations. The impact of changed radiation model input parameters on the calculated photolysis frequencies vary not only with regard to the changed parameter but also with regard to the to the species to be dissociated. Furthermore the impact of different sets of photolysis rates employed in a chemical transport simulation on the modelled concentrations is differed and likely to be less important than other aspects of the simulation like the resolution of the grid and the emissions used. Apart from major surface albedo changes (grass to snow) and extreme changes in total ozone column content for JO3 clouds are the dominating factor in modifying the photolysis frequencies especially as they feature a highly temporal and special variation. The results show that simulated maximum ozone concentrations in areas with clouds are reduced