αTub84B promoter sequences drive expression of lacZ that is tagged at the N-terminal end with Tag:NLS(SV40-largeT). Reconstituted in vivo by FLP-mediated recombination between the FRT sites present in the deletion derivatives P{5'CXY21.29}X15 and P{3'CXY21.4a}X15.
Used as marker for mosaic analysis in embryos.