The complete mitochondrial genome sequence of white perch Morone americana (Perciformes, Moronidae)

Identification of an IgD/IgT chimera in the European sea bass (Dicentrarchus labrax L.)

Three classes of immunoglobulins have been identified in Teleosts: IgM, IgT/Z and IgD. They are fundamental for fish immune responses and, therefore, their functional activities are heavily investigated. In this paper, we describe the identification of a new IgD/IgT chimera in sea bass (Dicentrarchus labrax) from a gills transcriptome. This transcript joined the first six constant domains of the IgD chain with the two terminal constant domains of IgT, generating a long in-frame coding sequence with a junction between the canonical δ6 exon splicing donor site and the τ3 exon splicing acceptor site. Studies performed on genomic DNA confirmed the presence of the sequence and identifies and intronic region of 656 bp within this joining region. The basal expression of the IgD/IgT chimera was investigated both in silico and in vivo: high level of expression was found in gills, gut and head kidney. Moreover, IgD/IgT transcripts were up-regulated after in vitro stimulation of sea bass HK leukocytes with LPS. The IgD/IgT chimera was found also in two congener species, Morone saxatilis and Morone chrysops. It is not possible to have a precise idea on the evolutionary scenario that lead to the appearance of this sequence due to the lack of genomic information, but we could speculate that an ancestral duplication of the entire IgH locus was followed by the chimerization of Cδ/Cτ in one of the two loci. Finally, the IgD/IgT high basal expression in tissues and organs fundamental for sea bass immune response and its modulation after LPS stimulation provide a very preliminary indication that this unusual Ig variant could have a functional activity.

The complete mitochondrial genome of Epinephelus Chlorostigma (Serranidae; Epinephelus) with phylogenetic consideration of Epinephelus

The complete mitochondrial genome of Epinephelus chlorostigma has been determined. It contains a typically conserved structure including 13 protein-coding genes, 22 tRNA genes, two rRNA genes and one control region, and the whole sequence was 16,894 bp in length. The overall base composition is A 28.70%, C 27.99%, G 16.28%, T 27.03%. Except ND6 and eight tRNA genes, all other mitochondrial genes are encoded on the heavy strand. Phylogenetic tree was constructed based on 12 protein-coding genes sequences of 18 Epinephelus species, four species belong to Cephalopholis as outgroup, the result showed that E. chlorostigma is most closely related to Epinephelus areolatus. We sequenced the complete mitochondrial genome of E. chlorostigma to enrich the resource of molecular markers for examination of phylogenetic relationships in Epinephelus.