9 research outputs found
The Phylogenetic Origin of oskar Coincided with the Origin of Maternally Provisioned Germ Plasm and Pole Cells at the Base of the Holometabola
The establishment of the germline is a critical, yet surprisingly evolutionarily
labile, event in the development of sexually reproducing animals. In the fly
Drosophila, germ cells acquire their fate early during
development through the inheritance of the germ plasm, a specialized maternal
cytoplasm localized at the posterior pole of the oocyte. The gene
oskar (osk) is both necessary and
sufficient for assembling this substance. Both maternal germ plasm and
oskar are evolutionary novelties within the insects, as the
germline is specified by zygotic induction in basally branching insects, and
osk has until now only been detected in dipterans. In order
to understand the origin of these evolutionary novelties, we used comparative
genomics, parental RNAi, and gene expression analyses in multiple insect
species. We have found that the origin of osk and its role in
specifying the germline coincided with the innovation of maternal germ plasm and
pole cells at the base of the holometabolous insects and that losses of
osk are correlated with changes in germline determination
strategies within the Holometabola. Our results indicate that the invention of
the novel gene osk was a key innovation that allowed the
transition from the ancestral late zygotic mode of germline induction to a
maternally controlled establishment of the germline found in many holometabolous
insect species. We propose that the ancestral role of osk was
to connect an upstream network ancestrally involved in mRNA localization and
translational control to a downstream regulatory network ancestrally involved in
executing the germ cell program
The Importance of Homology for Biology and Philosophy
Editors' introduction to the 2007 special issue of ‘Biology and Philosophy’ (volume 22, issue 5), which features papers presented as part of the symposium ‘The Importance of Homology for Biology and Philosophy’ at ISHPSSB 2007 (July 25-29, Exeter)