Maria J. Gravato-Nobre and Jonathan Hodgkin. In mammals, the skin and the epithelia lining mucosal tissues act as a primary nonspecific barriers serving to sense potentially harmful pathogens. In genetic screens we have identified
bus-1, a novel acyltransferase 3 family member, whose product is required for the nematode sensitivity to the bacterial pathogen Microbacterium nematophilum. Mutations in
bus-1 prevent bacterial attachment and subsequent post-anal cell swelling in C. elegans.
bus-1 encodes a transmembrane protein, with a domain present in many uncharacterized C. elegans proteins. Consistent with its function in hindgut establishment/maintenance, the
Cel-bus-1 is expressed during late embryogenesis and post-embryonically, in the rectal epithelium.. The specific expression pattern observed with reporter constructs makes
bus-1 a valuable hindgut marker for morphological and developmental studies, and in particular, in situations where the shape or the dimension of the rectal epithelial cells is to be inspected.. We show that incorrect specification of rectal epithelium in
egl-38 mutants has both positive and negative effects on
bus-1 expression. In contrast, expression is not affected by
egl-5.
bus-1 is also repressed by two transcription factors
mab-23 and
mab-9. Furthermore, we have observed that mutations in
mab-9 render the worms hypersensitive to M. nematophilum. We constructed double mutants of
bus-1 and
mab-9 and observed that the bacterial adhesion to the rectum is restored in these animals, showing that
bus-1 is not essential for infection. Bus-1 mutants exhibit no obvious defects, other than infection resistance. Nevertheless,
bus-1 is highly conserved. We found a
Cel-bus-1 ortholog that functionally rescues
Cel-bus-1 mutants, and shows the same rectal expression pattern, plus expression in vulval cells. We propose that BUS-1 is involved in post-translational modifications of a surface-exposed molecule, which acts as player in Cel-M. nematophilum recognition events. Our findings have implications for our understanding of host factors required for bacterial adhesion to epithelial mucosa.