The immune gene repertoire encoded in the purple sea urchin genome

Echinoderms occupy a critical and largely unexplored phylogenetic vantage point from which to infer both the early evolution of bilaterian immunity and the underpinnings of the vertebrate adaptive immune system. Here we present an initial survey of the purple sea urchin genome for genes associated with immunity. An elaborate repertoire of potential immune receptors, regulators and effectors is present, including unprecedented expansions of innate pathogen recognition genes. These include a diverse array of 222 Toll-like receptor (TLR) genes and a coordinate expansion of directly associated signaling adaptors. Notably, a subset of sea urchin TLR genes encodes receptors with structural characteristics previously identified only in protostomes. A similarly expanded set of 203 NOD/NALP-like cytoplasmic recognition proteins is present. These genes have previously been identified only in vertebrates where they are represented in much lower numbers. Genes that mediate the alternative and lectin complement pathways are described, while gene homologues of the terminal pathway are not present. We have also identified several homologues of genes that function in jawed vertebrate adaptive immunity. The most striking of these is a gene cluster with similarity to the jawed vertebrate Recombination Activating Genes 1 and 2 (RAG1/2). Sea urchins are long-lived, complex organisms and these findings reveal an innate immune system of unprecedented complexity. Whether the presumably intense selective processes that molded these gene families also gave rise to novel immune mechanisms akin to adaptive systems remains to be seen. The genome sequence provides immediate opportunities to apply the advantages of the sea urchin model toward problems in developmental and evolutionary immunobiology

El primer genoma mitocondrial completo de Diadema antillarum (Diadematoida, Diadematidae)

The mitochondrial genome of the long-spined black sea urchin, Diadema antillarum, was sequenced using Illumina next-generation sequencing technology. The complete mitogenome is 15,708 bp in length, containing two rRNA, 22 tRNA and 13 protein-coding genes, plus a noncoding control region of 133 bp. The nucleotide composition is 18.37% G, 23.79% C, 26.84% A and 30.99% T. The A + T bias is 57.84%. Phylogenetic analysis based on 12 complete mitochondrial genomes of sea urchins, including four species of the family Diadematidae, supported familial monophyly; however, the two Diadema species, D. antillarum and D. setosum were not recovered as sister taxa.El genoma mitocondrial del erizo de mar negro de espinas largas, Diadema antillarum, se secuenció utilizando la tecnología de secuenciación de nueva generación de Illumina. El mitogenoma completo tiene un tamaño de 15,708 pb, que contiene dos ARNr, 22 ARNt y 13 genes codificadores de proteínas, además de una región de control no codificante de 133 pb. La composición de nucleótidos es 18.37% G, 23.79% C, 26.84% A y 30.99% T. El sesgo A+T es del 57.84%. El análisis filogenético basado en 12 genomas mitocondriales completos de erizos de mar, incluyendo cuatro especies de la familia Diadematidae, apoya la monofilia familiar. Sin embargo,  las dos especies de Diadema en este estudio,  D. antillarum y D. setosum no fueron identificadas como taxones hermanos

The genome of the sea urchin Strongylocentrotus purpuratus

We report the sequence and analysis of the 814-megabase genome of the sea urchin Strongylocentrotus purpuratus, a model for developmental and systems biology. The sequencing strategy combined whole-genome shotgun and bacterial artificial chromosome (BAC) sequences. This use of BAC clones, aided by a pooling strategy, overcame difficulties associated with high heterozygosity of the genome. The genome encodes about 23,300 genes, including many previously thought to be vertebrate innovations or known only outside the deuterostomes. This echinoderm genome provides an evolutionary outgroup for the chordates and yields insights into the evolution of deuterostomes

Radiocesium concentrations and DNA strand breakage in two species of amphibians from the Chornobyl exclusion zone

Relatively few studies have considered impacts of the 1986 nuclear accident at Chornobyl on lower vertebrate populations. Amphibians are recognized as sensitive indicators of environmental degradation and pollution, and some amphibian population declines may be associated with contaminant-induced stress. Amphibians also utilize both aquatic and terrestrial habitats, which facilitates comparison of radionuclide accumulation and effects in different environments. We sampled sympatric frog species from a highly contaminated area within the Chornobyl exclusion zone and from a nearby, less contaminated area in August - September 1999. Radiocesium was measured in whole frogs and in muscle samples. Whole body mean radiocesium for Rana esculenta from Gluboke Lake, a highly contaminated area, was 22.3 Bq/g wet mass; R. terrestris from the same area contained 53.4 Bq/g wet mass. Radiocesium levels in frogs from Emerald Camp, a less contaminated area, were about an order of magnitude lower. In both locations, whole body radiocesium concentrations were higher in R. terrestris than in R. esculenta, probably reflecting dietary differences between species. Mean muscle radiocesium concentrations were generally lower than whole body concentrations, and muscle and whole body concentrations were highly correlated within individuals. We used pulsed field-gel electrophoresis to examine the size distribution of DNA fragments in muscle tissue from a subsample of R. terrestris from both locations. Increased proportions of smaller DNA fragments, suggesting DNA strand breakage, occurred in R. terrestris from the more contaminated location. Results support the concept that amphibians are useful in assessing radionuclide accumulation and effects in contaminated areas. However, differences among species must be considered in evaluating contaminant concentrations and potential effects