Insects express a battery of potent antimicrobial proteins in response to i
njury and infection. Recent work from several laboratories has demonstrated
that this response is neither stereotypic nor completely nonspecific, and
that different pathways are responsible for inducing the expression of anti
fungal and antibacterial peptides. Here we report the cloning of two closel
y linked attacin genes from Drosophila melanogaster. We compare their prote
in coding sequences and find the amino acid sequences to be more highly con
served than the nucleotide sequences, suggesting that both genes are expres
sed. Like other antimicrobial peptides, attacin expression is strongly indu
ced in infected and injured flies. Unlike others, attacin transcription is
uniquely sensitive to mutations in the 18-Wheeler receptor protein, and thu
s may be regulated by a distinct signaling pathway. The number and organiza
tion of binding sites for kappa B and other transcription factors in the pr
omoter regions of both attacin genes are consistent with strong and rapid i
mmune induction. We demonstrate that these promoter regions are sufficient
to direct beta-galaclosidase expression in transformed Drosophila third-ins
tar larval fat body in a bacterially inducible manner. We present a compari
son of the promoter regions of the two attacin genes to those cloned from o
ther antimicrobial peptide genes to assist a better understanding of how an
timicrobial genes are differentially regulated. (C) 2000 Elsevier Science B
.V. All rights reserved.