PICTURE: Scientists at the University of Cologne found that the Toll signal path is not only important for the innate immune response, but also for the formation of axes in various insects. view More
Photo credit: Roth / Pechmann
Certain signal proteins, which are responsible for the development of the innate immune function in almost all animals, are also required for the formation of the dorsal-ventral axis (back abdomen) in insect embryos. A new study by researchers from the Zoological Institute of the University of Cologne suggests that the relevance of these signal proteins for the formation of the insect axis during evolution has increased many times over, independently of one another. For example, the research team found similar evolutionary patterns in the Mediterranean field cricket as in the fruit fly Drosophila, although the two insects are only very far apart and previous observations suggested different evolutionary patterns. The new findings show that the development of axis formation in insects was actually much more complex than previously assumed. The study was published in eLife.
Signaling proteins play an important role in the early development of embryos. They are excreted by animal cells in order to influence the formation of other cells. The main function of the so-called Toll signal path is the defense against pathogens (innate immune response). In insects, it is also involved in the division of the insect’s body along the dorsal-ventral axis of the body. Since the immune function was found in almost all animals, but the axis-forming function only in insects, the scientists wondered about the evolutionary history of this new role. In addition, the importance of toll for development processes differs depending on the species of insect. While the axis formation in fruit flies and meal beetles depends largely on Toll, representatives of distant related species such as the wasp Nasonia and the milkweed tail Oncopeltus rely more on other signaling pathways. “Surprisingly, we found that the Toll signaling pathway plays an important role in an insect that is almost 400 million years away from the species studied so far,” said Professor Dr. Siegfried Roth from the Institute for Zoology. ‘The new study suggests that there could be multiple instances where Toll independently performed important functions in the formation of insect axes. For future studies, this means that our system will allow us to explore mechanisms of parallel evolution. ‘
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