UAS regulates expression of a split-GFP-based sensor for contact sites between mitochondria and ER with a 40-50 nm range. It is composed of spGFP11 localized to the ER and spGFP1-10 targeted to the outer mitochondrial membrane. When mitochondria and ER are in close proximity, reconstitution of split-GFP results in fluorescence. It is similar to P{UAS-SPLICS.s} but has a slightly longer spacer for reporting wider contact sites.