f57f4.4p::gfp as a fluorescent reporter for analysis of the C. elegans response to bacterial infection.

Host defense mechanisms are multi-layered and involve constitutive as well as inducible components. The dissection of these complex processes can be greatly facilitated using a reporter gene strategy with a transparent animal. In this study, we use Caenorhabditis elegans as a model host and introduce a new pathogen-inducible fluorescent reporter involving the promoter of f57f4.4, a gene encoding a putative component of the glycocalyx. We show that this reporter construct does not respond to heavy metal or hypertonic environments, but is specifically and locally induced in the intestine upon Photorhabus luminescens and Pseudomonas aeruginosa infections. We further demonstrate that its upregulation requires live pathogens as well as elements of the nematode p38 MAP kinase and TGF-beta pathways. In addition to introducing a new tool for the study of the interactions between C. elegans and a pathogen, our results suggest a role for the glycocalyx in gut immunity.