Two branches of innate immune response have evolved in Drosophila to recognize molecular patterns encoded either in fungi or in the cell walls of bacteria. Each activates distinct sets of genes encoding peptides with specific antimicrobial activity. Choe et al. investigated two mutant alleles (ird71 and ird72) that inhibited genes normally activated by the imd pathway by preventing the cleavage and nuclear translocation of the transcription factor Relish. The ird7 alleles mapped to a region of chromosome 3 containing peptidoglycan recognition protein (PGRP) genes and encoded truncations in PGRP-LC that could account for disruption of its function in each of the mutants. Phenotype rescue by transgenic overexpression of wild-type PGRP-LC in ird7 mutant flies and RNA interference analyses in cell lines confirmed that PGRP-LC is a critical component of the antimicrobial response of Drosophila.
K.-M. Choe, T. Werner, S. Stöven, D. Hultmark, K. V. Anderson, Requirement for a peptidoglycan recognition protein (PGRP) in Relish activation and antibacterial immune responses in Drosophila, Science 296, 359-362 (2002). [Abstract] [Full Text]