Germline cells are unique as they can produce gametes and regenerate themselves, and can be specified by either maternally inherited determinants or by zygotic inductive signals. In the maternal inheritance mode, the germ cells are specified very early by the germ plasm synthesized during oogenesis. This mode is found in most model organisms (fruit fly, zebrafish, frog and nematode), whereas the zygotic induction mode, may be the ancestral model of germline determination .
Among the invertebrates, the only arthropod in which the germ line has been studied in detail is Drosophila melanogaster which uses the maternal inheritance mode. However, this mechanism of germ cell specification is a derived feature in insects and seems to be limited Holometabola. The wasp Nasonia, like Drosophila, uses the maternal inheritance mode, and represents the most distantly branching holometabolous lineage relative to Drosophila. The assembly of Nasonia’s germ plasm is dependent on a regulatory network that is very similar to that of Drosophila, and occurs in the same context of polytrophic ovaries, indicating that a regulatory network similar to both fly and wasp was present ancestrally in the Holometabola. Despite the overall similarity Nasonia and Drosophila germline determination, some aspects are quite distinct, such as the morphology of the germ plasm, the formation of the pole cells, and the migration of the pole cells into the embryo interior.
To characterization the ancestral and novel features of Nasonia germplasm relative to Drosophila at the molecular the mRNA composition of the Nasonia oosome, was characterized by RNAseq. The results confirmed that certain genes, such as oskar, nasos, etc., are conserved between the two species, and also revealed previously unknown genes, which could be crucial for the unique properties of Nasonia germ plasm and germline.