Comparative Analysis of Nematode Defaecation Motor Program

The nervous system controls most rhythmic behaviours, with one remarkable exception. The defaecation motor program (DMP) in C. elegans is initiated by intestinal cells' pacemaker without participation of the nervous system. Our study on Heterorhabditis megidis and Enoplus brevis demonstrates that DMP machinery is not a unique feature of C. elegans. In C. elegans the role of several genes important for DMP has been experimentally studied. PBO-5/PBO-6 proton-gated ion channel mediates the signal transduction from gut cells to body muscles. We found homologues for this protein in other nematodes and demonstrated pH sensitivity of E. brevis body muscles. These and other DMP hallmark proteins NLP-40, AEX-2 and EXP-1 are also found in E. brevis and other species but not outside nematodes. Some nematodes lack individual proteins of DMP toolkit. For example, mermithids with degenerated digestive systems and with no through gut lost them all. Different nematode species possess the same non-nervous rhythmical DMP mechanism that evolved in the nematode common ancestor.