The Drosophila gene torso encodes a putative receptor tyrosine kinase.

The maternal gene torso, required for determination of anterior and posterior terminal structures in the Drosophila embryo, was cloned using P-element tagging. Genetic evidence suggests that the action of the gene product is spatially restricted to the terminal regions; the torso messenger RNA, however, is evenly distributed. Structural similarities of the predicted torso protein with growth-factor receptor tyrosine kinases suggest that the spatial restriction of torso activity results from a localized activation of the torso protein at the anterior and posterior egg pole.