Controlled expression of Drosophila homeobox loci using the Hostile takeover system

Background: Hostile takeover (Hto) is a Drosophila protein trapping system that allows the investigator to both induce a gene and tag its product. The Hto transposon carries a GAL4-regulated promoter expressing an exon encoding a FLAG-mCherry tag. Upon expression, the Hto exon can splice to a downstream genomic exon, generating a fusion transcript and tagged protein. Results: Using rough-eye phenotypic screens, Hto inserts were recovered at eight homeobox or Pax loci: cut, Drgx/CG34340, Pox neuro, araucan, shaven/D-Pax2, Zn finger homeodomain 2, Sex combs reduced (Scr), and the abdominal-A region. The collection yields diverse misexpression phenotypes. Ectopic Drgx was found to alter the cytoskeleton and cell adhesion in ovary follicle cells. Hto expression of cut, araucan, or shaven gives phenotypes similar to those of the corresponding UAS-cDNA constructs. The cut and Pox neuro phenotypes are suppressed by the corresponding RNAi constructs. The Scr and abdominal-A inserts do not make fusion proteins, but may act by chromatin- or RNA-based mechanisms. Conclusions: Hto can effectively express tagged homeodomain proteins from their endogenous loci; the Minos vector allows inserts to be obtained even in transposon cold-spots. Hto screens may recover homeobox genes at high rates because they are particularly sensitive to misexpression.