Developmental regulation of BhSGAMP-1, a gene encoding an antimicrobial peptide in the salivary glands of Bradysia hygida (Diptera, Sciaridae).

It has recently become clear that the innate immune systems of insects and mammals are highly conserved; in general, these systems are stimulated upon infection by microorganisms. We found in the fly Bradysia hygida, a reiterated gene, which codes for a secretory peptide similar to plant-seed antimicrobial peptides. This gene BhSGAMP-1 is activated and expressed exclusively in the salivary glands of the larvae, while they are preparing to molt. In functional tests, synthetic BhSGAMP-1 peptide had broad spectrum antibiotic activity. Secretion of BhSGAMP-1 in the saliva could help prevent microbial infection during molting, by killing harmful microorganisms in the immediate vicinity of the animal. This is the first description of developmentally regulated defense peptide secretion in animals.