The acyltransferase gene bus-1 exhibits conserved and specific expression in nematode rectal cells and reveals pathogen-induced cell swelling.

Susceptibility to the rectal pathogen Microbacterium nematophilum provides a means of examining hindgut differentiation in C. elegans. Mutants of bus-1 are resistant to infection with this pathogen. We show here that bus-1 encodes a predicted acyltransferase expressed in rectal epithelial cells (K, F, and U), suggesting its involvement in regional surface modification. bus-1 reporter genes were used to show spatial regulation by hindgut developmental control genes: egl-38, mab-9, and mab-23. A bus-1::GFP reporter reveals the conspicuous rectal epithelial swelling induced by M. nematophilum. The C. briggsae ortholog of bus-1 exhibits conserved function and rectal expression, but it is expressed in vulval as well as rectal cells, correlated with pathogen adhesion to both vulval and rectal cells in this species. Another acyltransferase affecting bacterial adhesion, bus-18/acl-10, was also identified, which also shows strong rectal expression, but it is expressed in additional epithelial tissues and is required for general surface integrity.