sem-4 is expressed in all rectal cells in L1s hermaphrodites (i.e., Y, U, B, F, K, and K') and in all rectal cells, including P12.pa, in L3 or older worms.
Transgenic animals carrying this reporter showed strong fluorescence in the presumptive rectal epithelial cells K, F, and U. This localization was confirmed using a hindgut-specific marker, lin-48p::GFP, which expresses in the same cells.
This operon, when introduced as a transgene, fully restored bacterial adhesion and tail swelling to infected animals, and exhibited the same expression in cells K, F, and U, with a diffuse cytoplasmic distribution of the GFP reporter.
Expression of mpk-1::gfp was observed in the rectal epithelial cells, including F and U, in 100% of wild type L1 (16/16), L2 (19/19), L3 (15/15), L4 (21/21) and adult (16/16)worms.
In two independent transgenic lines, expression was observed in embryos, larvae and adults in the posterior body region near the anus and in the tail. In L1 larvae, expression was seen in the rectal blast cells B, Y, U, F and K. HSN also expressed LacZ.