DISTINCT SPATIAL AND TEMPORAL FUNCTIONS FOR PS INTEGRINS DURING DROSOPHILA WING MORPHOGENESIS

At the onset of pupariation in the Drosophila wing, the PS1 and PS2 in tegrins are expressed preferentially on the dorsal and ventral wing ep ithelia, respectively, Clonal analysis experiments have indicated that integrins are required to maintain the tight association of the wing surfaces, Surprisingly, we find that even in clones of cells lacking i ntegrins the wing layers become apposed early in metamorphosis, Howeve r, following the normal period of wing separation, large integrin muta nt clones do not become re-apposed in the pupa, and integrins are not organized in basal plaques in cells opposite a mutant clone, Paradoxic ally, our experiments indicate that at least one integrin function req uires different integrins on the dorsal and ventral wing surfaces, how ever in some cases both alpha(PS) subunits can function to some degree on each wing surface. Finally, overexpression of an alpha(PS) subunit throughout the wing leads to a dominant wing blister phenotype, and t he critical period for this phenotype is the beginning of pupariation. These data indicate that integrin requirements in wing morphogenesis can be separated into early (prepupal) and late (pupal) functions, The late function seems to reflect the traditional view of integrins as c ell-matrix adhesion proteins, The early requirement, which probably re quires dorsoventral segregation of PS1 and PS2, suggests functions for PS1 and PS2 in signaling events that regulate morphogenesis.