A NOVEL ALPHA-INTEGRIN SUBUNIT ASSOCIATES WITH BETA-PS AND FUNCTIONS IN TISSUE MORPHOGENESIS AND MOVEMENT DURING DROSOPHILA DEVELOPMENT

We hare identified a novel alpha integrin subunit in Drosophila, that associates with beta PS integrin, We report the temporal expression of the gene encoding this integrin subunit, which me have called alpha P S3, throughout development and the localization of its expression duri ng embryogenesis. alpha PS3 RNA was localized to tissues undergoing in vagination, tissue movement and morphogenesis such as salivary gland, trachea, midgut, dorsal vessel, midline of the ventral nerve cord, amn ioserosa and the amnioproctodeal invagination, alpha PS3 DNA localized to the chromosomal vicinity of scab (scb), previously identified by a failure of dorsal closure. Embryos homozygous for the 119 allele of s cb had no detectable alpha PS3 RNA and the 1035 allele of scb contains a P element inserted just 5' of the coding region for the shorter of the gene's two transcripts, Furthermore, mutations in the scb locus ex hibit additional defects corresponding to sites of alpha PS3 transcrip tion, including abnormal salivary glands, mislocalization of the peric ardial cells and interrupted trachea, Removal of both maternal and zyg otic beta PS produced similar defects, indicating that these two integ rin subunits associate in vivo and function in the movement and morpho genesis of tissues during development in Drosophila. Phenotypic simila rities suggest that laminin A is a potential ligand for this integrin, at least in some tissues.