Thirteen copies of the lexAop regulatory sequence are separated from a non-fluorescent 'spaghetti monster GFP' ('smGdP') marker by a KDRT cassette containing stop sequences, which prevents expression of the marker in the absence of KDR recombinase. The smGdP marker consists of 10 copies of the Tag:FLAG tag inserted in groups into the backbone of the superfolder green fluorescent protein, which has been rendered non-fluorescent by mutation. A N-terminal myristoylation signal (Tag:Myr(Src64B)) is also present and the marker has been optimised for Drosophila codon usage.