Dorsoventral pattering relies on Toll and BMP signalling in all insects studied so far, with variations in the relative contributions of both pathways. Drosophila and the beetle Tribolium share extensive dependence on Toll, while representatives of more distantly related lineages like the wasp Nasonia and bug Oncopeltus rely more strongly on BMP signalling. Here, we show that in the cricket Gryllus bimaculatus, an evolutionarily distant outgroup, Toll has, like in Drosophila, a direct patterning role for the ventral half of the embryo. In addition, Toll polarizes BMP signalling, although this does not involve the conserved BMP inhibitor Sog/Chordin. Finally, Toll activation relies on ovarian patterning mechanisms with striking similarity to Drosophila. Our data suggest two surprising hypotheses: 1) that Toll's patterning function in Gryllus and Drosophila is the result of convergent evolution or 2) a Drosophila-like system arose early in insect evolution, and was extensively altered in multiple independent lineages.
- Matthias Pechmann
- Yen-Ta Chen
- Thomas Buchta
- Thomas Buchta
- Orhan Özüak
- Jeremy A Lynch
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Patricia J Wittkopp, University of Michigan, United States
- Received: March 15, 2021
- Accepted: March 24, 2021
- Accepted Manuscript published: March 30, 2021 (version 1)
© 2021, Pechmann et al.
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