"Previous studies have shown that
hsp-4 expression is dramatically reduced in
xbp-1(ko) worms relative to wild-type after treatment with tunicamycin, an ER-stress inducer [28]. In accordance, we found a less than two-fold increase in
hsp-4::GFP expression in
xbp-1(ko);
icd-1(RNAi)-treated worms (Figure S1A,B), as compared with an almost five-fold increase in wt:
icd-1(RNAi) animals, when both were compared to untreated controls (Figure 2D), indicating that
xbp-1(ko) worms up-regulate
hsp-4 expression less efficiently than wild-type animals when both are depleted of ICD-1."