Evolution of the control pathways of tissue development in Diptera

Abstract

Larval imaginal discs are the precursors of adult organs in holometabolous insects. Hence, any damage in the discs that is not repaired would result in errors in the organ formation and may incapacitate the adult stage. Therefore, it is necessary to have control mechanisms of tissue development in larval individuals. An example of such mechanisms is the metamorphosis delay. Studies using Drosophila melanogaster larvae demonstrated that ILP8 protein is involved in this control, as its high concentrations delay the pupariationand ensure time for tissue recovery. Despite its importance, little is known about Ilp8 gene evolution among dipterans and its involvement in the metamorphosis delay. It is assumed that metamorphosis delay occurs since basal dipterans as a development control mechanism, but the Ilp8 gene is a Brachycera innovation. Moreover, it is not clear when ILP8's role in development has evolved. To understand the molecular basis and evolution of the delay mechanism, one of the best approaches is the comparison of gene expression in larvae with normal growth and larvae that had tissue damage during its development. Comparative RNA-seq assays of species with and without the Ilp8 ortholog will allow the investigation of when both, Ilp8 gene and function, has evolved. Furthermore, in species that do not have its ortholog, which genes are involved in this metabolic pathway.