BackgroundA recent study by Barthélémy et al. described a set of ribosomal protein (RP) genes extracted from a collection of expressed sequence tags (ESTs) of the chaetognath (arrow worm) Spadella cephaloptera. Three main conclusions were drawn in this paper. First, the authors stated that RP genes present paralogous copies, which have arisen through allopolyploidization. Second, they reported two alternate nucleotide stretches conserved within the 5' untranslated regions (UTR) of multiple ribosomal cDNAs and they suggested that these motifs are involved in the differential transcriptional regulation of paralogous RP genes. Third, they claimed that the phylogenetic position of chaetognaths could not be accurately inferred from a RP dataset because of the persistence of two problems: a long branch attraction (LBA) artefact and a compositional bias.
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