G. Kovalick, C. Brown, R. Jay, and J. Nathan. Members of the CAP family are usually secreted and frequently have roles in modulating an immune response. All CAP family proteins share a sequence motif that seems to confer a very stable tertiary structure, allowing these proteins to function in very harsh environments. The Agr gene begins to be expressed within a restricted region of the proventriculus during late embryogenesis. The domain of expression expands during the larval stage and is maintained until the prepupal stage.
Expression is reinitiated within the proventriculus following eclosion.
We are interested in how functional domains are established within the gut during development and are investigating the genetic and physiological factors that activate Agr expression during the embryonic, larval, and adult stages. The pattern of Agr expression suggests that its gene product functions within the gut, probably as a component of the peritrophic matrix, a tubular envelope made up of chitin, proteoglycans, and glycoproteins that separates the midgut epithelium from ingested food. We are interested in the role of the peritrophic matrix as a barrier to pathogens. Given its similarity to proteins known to act as immune modulators, we suggest that the Agr gene product functions as an antimicrobial protein within the peritrophic matrix and are examining this hypothesis using mutants that lack a functional Agr gene.