Meeting Abstract
For mature gametes to form, the first precursors of the sex cell lineage must be specified and correctly localized during embryonic development. These precursors are known as Primordial Germ Cells (PGCs). Among insects, the molecular basis of PGC specification and migration has been well-characterized largely in Drosophila melanogaster. However, Drosophila germ cells (pole cells) are formed by a derived mechanism which relies on the inheritance of a maternally localized cytoplasm (germ plasm) at the egg posterior. This mechanism is not thought to be a representative mechanism of PGC specification among insects. To understand the putative ancestral mechanism for specifying PGCs, we must pursue functional genetic studies in a broader sampling of taxa. To this end, we have chosen the large milkweed bug (Oncopeltus fasciatus), as it lies within a sister order (Hemiptera) to the holometabolous insect orders. Embryological and gene expression data suggest that O. fasciatus does not have a germ plasm, leading to the hypothesis that it specifies its PGCs by inductive signaling. In this insect, PGCs are first located at the posterior of the embryo proper, and appear to migrate anteriorly before localizing in abdominal segments A4-A6. It is unknown whether these cells are actively migrating during this process. The factors responsible for directing these cells are also unknown. Members of the Bone Morphogenetic Protein (BMP) pathway instruct PGCs to form in mice (Mus musculus) and crickets (Gryllus bimaculatus), and across animals, evidence indicates that this pathway is important for various aspects of reproductive development. We hypothesize that BMP signals are instructing the specification and/or the migration of the PGCs in O. fasciatus. Here we present our progress in using RNA interference to test this hypothesis.
