It is not clear how simple genetic changes can account for the coordinated variations that give rise to modified functional organs. Here, we addressed this issue by analysing the expression and function of regulatory genes in the developing tracheal systems of two insect species. The larval tracheal system of Drosophila can be distinguished from the less derived tracheal system of the beetle Tribolium by two main features. First, Tribolium has lateral spiracles connecting the trachea to the exterior in each segment, while Drosophila has only one pair of posterior spiracles. Second, Drosophila, but not Tribolium, has two prominent longitudinal branches that distribute air from the posterior spiracles. Both innovations, while considered different structures, are functionally dependent on each other and linked to habitat occupancy. We show that changes in the domains of spalt and cut expression in the embryo are associated with the acquisition of each structure. Moreover, we show that these two genetic modifications are connected both functionally and genetically, thus providing an evolutionary scenario by which a genetic event contributes to the joint evolution of functionally inter-related structures.
The authors declare no competing or financial interests.
Conception and design of the project: C.d.M., F.L., J.C. and X.F.-M. Performed experiments: C.d.M. and F.L. Analysis of the data: C.d.M., F.L., J.C. and X.F.-M. The manuscript was written by J.C. with the support of X.F.-M. All authors were involved in discussions and commented on the manuscript.
This work was supported by the Ministerio de Ciencia e Innovacion (MICINN) BFU2009-07629 to C.d.M., J.C. and F.L.; Consolider-Ingenio 2010 program to J.C; BFU2009-08748 to X.F.-M; and FEDER funds]; Obra Social ‘la Caixa’ Foundation (F.L.); Generalitat de Catalunya to X.F-M. [CGL2014-55786-P] and to J.C.
Supplementary information available online at http://dev.biologists.org/lookup/doi/10.1242/dev.134924.supplemental
- Received January 8, 2016.
- Accepted August 12, 2016.