Phylogeny and organization of 5’ exons in <i>PRKACA/PRKACB</i> homologs.

<p>(A) The branching diagram (left) shows the major vertebrate classes or representative species from major classes and their evolutionary relationship. The organization of the different 5’ exons in <i>PRKACA</i> for each branch was determined based on data from genomic and transcriptomic sequence databases. Exons 1–1 (green), 1-L (red), and 1-S (blue) are represented as boxes and reflect the genomic ordering of 5’ exons encoding the Cα1, CαL and short Cα transcript variants, respectively. Exon 2 (black) is conserved in all species [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181091#pone.0181091.ref022" target="_blank">22</a>]. Exons that could not be placed due to missing genomic sequence coverage are also shown (Unplaced exons). In mammals, 1-S is identical to exon 1–2 encoding the Cα2 sperm-specific variant, and is conserved in all major mammalian groups. It is not possible to determine whether or not mammalian exon 1–2 is orthologous to the short 1-S exons in non-mammalian classes. CαL-specific sequences were not identified in mammals and birds, the most parsimonious explanation being two separate deletion events in these groups, as indicated by arrows. (B) For all major vertebrate groups shown in panel A, the organization of 5’ exons 1–1 (green) and 1–2 (red) in <i>PRKACB</i> are identical. In addition, several short exons 1-S (blue, dashed boxes) were identified in <i>PRKACB</i> between exon 1–2 and exon 2 (black). (C) The duplication of an ancestor C subunit gene occurred around the evolution of the first vertebrate species (arrow). 1-L and 1-S specific <i>PRKACA</i> exons and 1-S specific <i>PRKACB</i> exons not identified in all vertebrate groups are shown as dashed boxes. The exons p, 1V2, 1V3, L1, L2, and L3 denote various 5’ exons found in invertebrate species only. The tree shows tunicates as the closest living relatives of vertebrates [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181091#pone.0181091.ref046" target="_blank">46</a>], and the echinoderm sea urchin and hemichordate acorn worm (<i>Saccoglossus kowalevskii</i>) as belonging to sister phyla [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0181091#pone.0181091.ref047" target="_blank">47</a>].