Induction of ire-1-xbp-1 pathway's role in response to PFT but not unfolded proteins is regulated by the p38 MAPK pathway ER stress responses have been studied extensively for their role in protecting cells against unfolded proteins [10, 18] . One way to assess the role of the ER stress pathways in protecting against unfolded proteins is with the drug tunicamycin (a natural compound that leads to the accumulation of unfolded proteins in the ER due to its inhibitory effect on N-linked protein glycosylation [19] ). Previous data in C. elegans have indicated different sensitivities of the three ER stress response pathways for tunicamycin [11, 12] . Using a different toxicity assay, we have confirmed these observations: atf-6(ok551) mutant animals have a similar sensitivity to tunicamycin as wild-type animals whereas both xbp-1(zc12) and pek-1(ok275) mutant animals are more readily killed by tunicamycin (Figure 4) . These results are in contrast to the response of these different ER stress pathways to Cry5B, to which atf-6 mutant animals are more sensitive than pek-1 mutant animals. These data suggest that there are differences in how ER stress pathways are activated in response to unfolded proteins and to the PFT Cry5B. It is known that PFTs trigger the activation of p38 MAPK, which promotes cell survival and cellular defenses and which seems to play a central role in cellular responses to PFTs [6, 7, 20] . We therefore investigated whether PFT-mediated activation of the UPR and the p38 MAPK pathway might be connected.