RESUMEN
Recently we have shown that BhSGAMP-1 is a developmentally regulated reiterated gene that encodes an antimicrobial peptide (AMP) and is expressed exclusively in the salivary glands, at the end of the larval stage. We show, for the first time, that a gene for an AMP is directly activated by 20-OH ecdysone. This control probably involves the participation of short-lived repressor(s). We also found that the promoter of BhSGAMP-1 is not equipped with elements that respond to infection, provoked by the injection of microorganisms, in the salivary glands or in the fat body. We produced polyclonal antibodies against the synthetic peptide and found that the BhSGAMP-1 peptide is secreted in the saliva. The BhSGAMP-1 gene was also activated during the third larval molt. These facts confirm our hypothesis that this preventive system of defense was selected to produce an environment free of harmful microorganisms in the insect's immediate vicinity, during molts.
Asunto(s)
Dípteros/genética , Ecdisterona/farmacología , Regulación del Desarrollo de la Expresión Génica/efectos de los fármacos , Proteínas de Insectos/genética , Glándulas Salivales/efectos de los fármacos , Proteínas y Péptidos Salivales/genética , Animales , Western Blotting , Dípteros/metabolismo , Dípteros/microbiología , Ecdisterona/fisiología , Electroforesis en Gel de Poliacrilamida , Escherichia coli/fisiología , Interacciones Huésped-Patógeno , Proteínas de Insectos/metabolismo , Larva/efectos de los fármacos , Larva/genética , Larva/microbiología , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Saccharomyces cerevisiae/fisiología , Glándulas Salivales/metabolismo , Proteínas y Péptidos Salivales/metabolismo , Staphylococcus aureus/fisiologíaRESUMEN
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.
