Dual role of BgFTZ-F1 during nymphal development in the hemimetabolous insect Blattella germanica

Abstract

In insects, the ecdysteroidal hormone 20-hydroxyecdysone (20E) controls key developmental processes during embryogenesis, molting, metamorphosis and reproduction, as it has been extensively studied in holometabolous insects, especially in Drosophila melanogaster. The situation is very different in hemimetabolous insects, which do not develop through complete metamorphosis, their juvenile forms being morphologically similar to the adult. Indeed, in hemimetabolous insects the wealth of information concerning the molecular basis of the 20E-triggered genetic hierarchy is practically non-existent. However, if we aim to understand the molecular basis of the evolution towards complete metamorphosis in insects, then characterization of the 20E-induced genetic hierarchy in primitive species becomes of paramount importance. In the cockroach Blattella germanica, we have previously characterized the two components of the heterodimeric ecdysone receptor, as well as several early and early-late genes. In the present work we extend the knowledge of the 20E genetic hierarchy in B. germanica by identifying a FTZ-F1 homologue in this cockroach, by studying its regulation by ecdysteroids and by determining its functions in nymphal development with RNAi approaches. RNAi experiments reveal that FTZ-F1 is required to molt and to control the timing of ecdysteroid production during the last nymphal stage.