| Popis: |
Two conserved pathways (Toll and BMP) pattern the embryonic DV axis of Drosophila melanogaster. The Toll pathway dominates this process and is the source of all polarity and most of the patterning along the DV axis of the embryo. This is in contrast to other animals, where Toll signalling is not employed for DV patterning, and BMP signalling plays the major role. The early patterning role of Toll can therefore be considered as an evolutionary novelty, which appeared within the insect lineage. To further investigate the evolution of axial patterning in insects we analyzed the DV axis of the wasp Nasonia vitripennis, which is a member of the Hymenoptera, the most basally branching order of the Holometabola. A detailed analysis of the expression of DV marker genes that cover the entire embryonic axis revealed that the expression pattern just prior to the onset of gastrulation is almost identical in Nasonia and Drosophila. However, in Nasonia these patterns are initially very dynamic and evolve over time, which indicates that the upstream network for generating this pattern is highly diverged. In order to examine the functional basis of DV patterning in Nasonia we knocked down Toll and BMP signalling and showed that BMP is required for almost all DV patterning and that Toll has only a limited role. These results indicate that the ancestral role of Toll in insect embryos was only to induce mesoderm, while BMP played the dominant role. To further analyze and identify new target genes or possible new components of both pathways, we performed a transcriptome analysis of wild type, Toll knockdown, and BMP knockdown embryos. The outcome was a set of 262 genes that were significantly up or down regulated when compared among the different data sets. To analyze the expression pattern of those genes, we established a high throughput in situ technique. A first round of analysis revealed many interesting candidates that might play a role in DV patterning. However, further descriptive and functional analyses of all 262 identified genes are needed. |
