We are developing genetic and molecular tools to characterize genes involved in symbiosis and parasitism in the rhabditid nematode, Heterorhabditis bacteriophora; these important processes are currently not studied in C. elegans. The developmentally arrested infective juvenile (IJ) transmits Photorhabdus luminescens bacteria from the intestinal lumen to the insect hemocoel. The IJs employ the symbiotic bacteria to: 1) infect insects 2) grow and develop and 3) protect the insect cadaver from competing microbes, nematodes and insects. Because the IJs and symbiotic bacteria can be maintained on agar based media and the symbiont is amenable to genetics with a genome sequence, we sought to develop genetics in the nematode to take a balanced approach for the study of symbiosis and parasitism. Since a genetic and physical map is lacking in H. bacteriophora, we sought to develop RNAi as a reverse genetic technique to determine gene function. Using an EST dataset kindly provided by Ann Burnell (NUI, Maynooth), we choose 7 H. bacteriophora orthologs that had obvious RNAi phenocopies in C. elegans as were three others. Soaking L1 H. bacteriophora nematodes in dsRNA resulted in strong phenocopies for hb-
cct-2, hb-
icd-1, hb-
daf-21, hb-W01B11.3 and hb-W01G7.3 (penetrances of ~70-100%), moderate phenocopies for hb-
arf-1, hb-K04D7.1 (penetrances of ~30-50%) and no observable phenocopies for hb-
ben-1, hb-
mrp-4 and hb-
nhr-47. The resulting phenocopies were compared to C. elegans by feeding and found to be similar. These results demonstrate systemic RNAi in H. bacteriophora , which in the future can be applied to determine genes involved in symbiosis and parasitism.