Serpent regulates Drosophila immunity genes in the larval fat body throughan essential GATA motif

Insects possess a powerful immune system, which in response to infection le ads to a vast production of different antimicrobial peptides, The regulator y regions of many immunity genes contain a GATA motif in proximity to a kap pa B motif, Upon infection, Rel proteins enter the nucleus and activate tra nscription of the immunity genes. High levels of Rel protein-mediated Cecro pin A1 expression previously have been shown to require the GATA site along with the kappa B site, We provide evidence demonstrating that the GATA mot if is needed for expression of the Cecropin A1 gene in larval fat body, but is dispensable in adult fat body. A nuclear DNA-binding activity interacts with the Cecropin A1 GATA motif with the same properties as the Drosophila GATA factor Serpent. The GATA-binding activity is recognized by Serpent-sp ecific antibodies, demonstrating their identity. We show that Serpent is nu clear in larval fat body cells and haemocytes both before and after infecti on. After overexpression, Serpent increases Cecropin A1 transcription in a GATA-dependent manner. We propose that Serpent plays a key role in tissue-s pecific expression of immunity genes, by priming them for inducible activat ion by Rel proteins in response to infection.