zcIs4 [hsp-4::GFP] V. vit-4(ac4) is a dominant allele that causes ER stress. Since vit-4 is expressed only in adult stage, ER stress is induced only in adult stage. The levels of GFP expression from zcIs4 [hsp-4::GFP] reporter indicates the level of ER stress. Reference: Singh J & Aballay A. MBio. 2017 May 30;8(3). pii: e00778-17. doi: 10.1128/mBio.00778-17.