In insects, major developmental transitions occurring throughout their life cycles are finely regulated by changes in the titer of the ecdysteroidal hormone, 20-hydroxyecdysone (20E). 20E regulates these transitions upon binding to its heterodimeric receptor formed by two members of the nuclear receptor superfamily, EcR and the RXR homolog USP. In addition, the activated receptor elicits cascades of gene expression that mediate and amplify the ecdysteroidal signal. Molecular characterization of most of the cascade genes revealed that they encode transcription factors, namely E75, E74 and Broad complex. Here, we report the cloning and hormonal regulation of two isoforms of E74 from the hemimetabolous direct-developing insect Blattella germanica, namely BgE74A and BgE74B. Within the DNA-binding ETS domain of the protein, BgE74 is 95% similar to that of D. melanogaster homologue, whereas the 5‘-isoform-specific regions of BgE74A and BgE74B show significantly lower similarity. The two isoforms present characteristic expression patterns during embryo and nymphal development, and experiments in vitro with fat body tissue have shown that the two isoforms display specific 20E responsiveness. Finally, we characterized the functions of BgE74 during nymphal and adult development by using RNAi experiments in vivo.

Trabajo presentado en el 17th International Ecdysone Workshop, celebrado en Ulm (Alemania) del 20 al 24 de junio de 2008.

Peer Reviewed