INSECT IMMUNITY - A TRANSGENIC ANALYSIS IN DROSOPHILA DEFINES SEVERALFUNCTIONAL DOMAINS IN THE DIPTERICIN PROMOTER

Diptericins are antibacterial polypeptides which are strongly induced in the fat body and blood cells of dipteran insects in response to sep tic injury. The promoter of the single-copy, intronless diptericin gen e of Drosophila contains several nucleotide sequences homologous to ma mmalian cis-regulatory motifs involved in the control of acute phase r esponse genes. Extending our previous studies on the expression of the diptericin gene, we now report a quantitative analysis of the contrib ution of various putative regulatory elements to the bacterial inducib ility of this gene, based on the generation of 60 transgenic fly lines carrying different elements fused to a reporter gene, Our data defini tively identify two kappa B-related motifs in the proximal promoter as the sites conferring inducibility and tissue-specific expression to t he diptericin gene. These motifs alone, however, mediate only minimal levels of expression. Additional proximal regulatory elements are nece ssary to attain some 20% of the full response and we suspect a role fo r sequences homologous to mammalian IL6 response elements and interfer on-gamma responsive sites in this up-regulation. The transgenic experi ments also reveal the existence of a distal regulatory element located upstream of -0.6 kb which increases the level of expression by a fact or of five.