OMMATIDIAL POLARITY IN THE DROSOPHILA EYE IS DETERMINED BY THE DIRECTION OF FURROW PROGRESSION AND LOCAL INTERACTIONS

The adult eye of Drosophila is a highly ordered structure. It is compo sed of about 800 ommatidia, each displaying precise polarity. The omma tidia are arranged about an axis of mirror image symmetry, the equator , which lies along the dorsoventral midline of the eye. We use hedgeho g pathway mutants to induce ectopic morphogenetic furrows and use thes e as a tool to investigate the establishment of ommatidial polarity. O ur results show that ommatidial clusters are self-organising units who se polarity in one axis is determined by the direction of furrow progr ession, and which can independently define the position of an equator without reference to the global coordinates of the eye disc.