(a) Schematic representation of the Oskar gene. The LOTUS and OSK hydrolase-like domains are separated by a poorly conserved region of predicted high disorder and variable length between species. In some dipterans, a region 5’ to the LOTUS domain is translated to yield a second isoform, called Long Oskar. Residue numbers correspond to the D. melanogaster Osk sequence. (b) Stackplot of domain of life identity of HMMER hits across the protein sequence. For a sliding window of 60 Amino Acids across the protein sequence (X axis), the number of hits in the Trembl (UniProt) database (Y axis) is represented and color coded by domain of life origin (see Materials and methods: Iterative HMMER search of OSK and LOTUS domains), stacked on top of each other. (c, d) EFI-EST-generated graphs of the sequence similarity network of the LOTUS (c) and OSK (d) domains of Oskar (Gerlt et al., 2015). Sequences were obtained using HMMER against the UniProtKB database. Most Oskar LOTUS sequences cluster within eukaryotes and arthropods. In contrast, Oskar OSK sequences cluster most strongly with a small subset of bacterial sequences.