The UPR^ER is activated in aging intestines.

<p>(A) Expression of Gp93, Hsc70-3 and Xbp1 in guts from flies of different ages. Expression was determined using RNAseq in experiments described in <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004568#pgen.1004568-Guo1" target="_blank">[32]</a>. Expression values are shown normalized to the 2 d timepoint in the graph. Raw RPKM values are shown in the table. (B) Major branches of UPR^ER signaling pathways in <i>Drosophila</i>. (C) Young (5 day old) and old (30 day old) guts of esg::Gal4, UAS::GFP flies immunostained with anti-Hsc3 antibody (DNA: DAPI, blue; ISCs/EBs: GFP, green; Hsc3, red). The Hsc3 channel is shown separately on the right. (D) Reporter line <i>Xbp1_p</i>::<i>DsRed</i> visualizes expression of Xbp1 in young (3 day) and old (42 day) guts (DNA: DAPI, blue; ISCs/EBs: GFP, green; DsRed: red). The DsRed channel is shown separately on the right. (E) Enlarged images for intestines of young (5 day) and old (30 day) flies (esg::Gal4, UAS:: GFP/+) immunostained with anti-Hsc3 antibody (DNA: DAPI, blue; ISCs/EBs: GFP, green; Hsc3, red). White arrowheads indicate ISCs/EBs. The Hsc3 channel is shown separately on the right. (F) Xbp1 splicing reporter (UAS::Xbp1-EGFP) expressed in ISCs/EBs using esg::Gal4. Expression of GFP in young (5 day) and old (62 day) guts is shown. (DNA: DAPI, blue; GFP, green). The GFP channel is shown separately on the right. See also <a href="http://www.plosgenetics.org/article/info:doi/10.1371/journal.pgen.1004568#pgen.1004568.s001" target="_blank">Figure S1</a>.