Discovery of Defense- and Neuropeptides in Social Ants by Genome-Mining
Figure 4
Sequences, gene- and peptide structures of ant inotocins.
(A) Sequences of prepro-inotocin/neurophysin proteins from Atta cephalotes, Camponotus floridanus and Harpegnathos saltator were compared by similarity alignment to known inotocin/oxytocin/vasopressin prepro-proteins from Tribolium castaneum (UniProtKB A3RE83), Nasonia vitripennis (GenBank XP001606547.1), Homo sapiens (P01185 and P01178) and Lymnaea stagnalis (Q00945). The signal peptide cleavage site (identified by similarity) is shown with an arrow. Mature vasopressin/oxytocin/inotocin peptides are indicated in the box, followed by the canonical GRK amidation signal (dotted line above the sequences). The conserved cysteine residues in the neurophysin domain are indicated with asterisks. The sequence alignment was prepared using Boxshade. (B) Gene structure of novel H.saltator inotocin and known vasopressin-family prepro-protein genes (GenBank H.sapiens NC000020.10 and T.castaneum NC007423.2) was predicted using the GeneWise algorithm. Signal sequences are indicated in light grey, the mature peptide hormone chains (INT, inotocin; AVP, vasopressin; OT, oxytocin) in dark grey, pre-regions in black and the neurophysin domains in white. For the AVP prepro-protein the copeptin region is also marked. Intron sequences (including their base pair length) are indicated with upside-down arrow heads. (C) Evolution of the vasotocin nonapeptide family (simplified illustration for clarity, see also [42], [46]) is indicated by solid arrows. Arginine-vasotocin is the presumed ancestral peptide of oxytocin and vasopressin. Mammalian oxytocin evolved via intermediate forms of isotocin (bony fish) and mesotocin (lung fish, amphibians, reptiles and birds). It is yet to be determined whether invertebrate oxytocin/vasopressin-related peptides in insects or snails (e.g. conopressins, not shown) have also evolved from ancestral vasotocin (indicated as dashed line) [42]. The peptide sequences are shown in one-letter amino acid code. The highly conserved cysteine-residues and disulfide bonds are colored in yellow. Residues in the ancestral arginine-vasotocin and those that are identical to vasotocin are colored in dark grey. Residues that have changed during vasopressin evolution are colored in red, residues that have changed during oxytocin evolution are colored in purple and residues that are unique to insect/ant inotocins are colored in green.