To independently test this result, we analyzed the in vivo expression of an ire-1 regulated gene, hsp-4, a BiP homolog. In vivo analysis of the hsp-4 promoter coupled to green fluorescent protein (GFP) demonstrated expression of this gene requires ire-1 and xbp-1 [13] . A C. elegans strain containing hsp-4::GFP was fed either control E. coli or Cry5B expressing E. coli for 8 hours at 20uC. As shown, a strong and specific increase in GFP expression in the intestine can be seen in the presence of the PFT ( Figure 1B , middle panel), consistent with activation of the ire-1-xbp-1 pathway by Cry5B. Heat shock of this strain in the absence of Cry5B confirms GFP could be induced in other cell types in addition to the intestine ( Figure 1B, right panel) , as was demonstrated with the N-glycosylation inhibitor tunicamycin [13] . The fact that Cry5B only induced expression in intestinal cells suggests the PFT is only targeting these cells (see below).