The glp-4(bn2) strain was used for these experiments (including the double mutants glp-4(bn2);xbp-1(zc12) an glp-4(bn2); sek-1(km4)) since it has a greatly reduced number of germ cells when grown at Figure 6 . Schematic illustrating relationship between p38 MAPK, ire-1-xbp-1, and PFT defense pathways. PFTs at the cell surface of epithelial cells activate p38 MAPK that activates IRE-1 that induces splicing of xbp-1, which then turns on defense against PFTs. Residual activation of xbp-1 targets in the absence of the p38 MAPK pathway suggests there might be p38-independent activation of the ire-1-xbp-1 pathway in response to PFT as well (not shown). Independent of IRE-1 activation, p38 MAPK can also activate TTM-2 and other PFT defenses. Tunicamycin, which causes the accumulation of unfolded proteins in the ER, activates IRE-1 via a mechanism independent of the PFT and p38 MAPK. doi:10.1371/journal.ppat.1000176.g006