A tubulin promoter drives expression of vtd, which is tagged 12bp upstream of the translational stop codon with 10 copies of Tag:MYC. In addition, an SpeI site has been introduced into the vtd coding region after amino acid residue 550, and 3 tandem copies of the Tag:CS(TEVp) protein cleavage tag have been introduced into this site (this sequence allows cleavage of the vtd protein by TEV\NIa). The portion of the construct containing the vtd coding region and a 3'UTR sequence is flanked by an FRT cassette.