A ROLE FOR THE SEGMENT POLARITY GENE SHAGGY-ZESTE WHITE-3 IN THE SPECIFICATION OF REGIONAL IDENTITY IN THE DEVELOPING WING OF DROSOPHILA

The Drosophila segment polarity gene known as shaggy or zeste white 3 encodes a ubiquitously expressed serine-threonine protein kinase which is critical for a number of important developmental processes. In the developing wing blade, clones of cells lacking the normal shaggy-zest e white 3 product form dense tufts of margin-like bristles and bristle precursors. In a previous study I hypothesized that this phenotype co uld be best explained as a transformation in the regional identity of wing blade cells to one resembling that found along the normal wing ma rgin. A number of genes have recently been identified which are expres sed exclusively or at higher levels along the normal wing margin; in t his study I will show that two of these genes, vestigial and scalloped , are overexpressed at margin-like levels in shaggy-zeste white 3 clon es. This phenotype does not depend upon the formation of ectopic brist le precursors and occurs in clones lacking both shaggy-zeste white 3 a nd the entire achaete-scute complex. As vestigial and scalloped are bo th involved in early patterning events prior to the stages of bristle specification, these results strongly suggest that shaggy-zeste white 3 is required for the normal specification or maintenance of regional identity in the developing wing blade. The margin-like transformation is, however, partial, since the expression of apterous (in pupal wings ) and wingless and cut (at late third instar) was not reliably altered in shaggy-zeste white 3 clones. It has been suggested that shaggy-zes te white 3 is involved in a wingless signaling pathway in the embryo; a model is discussed in which shaggy-teste white 3 acts downstream of localized apterous and wingless expression to specify or maintain marg in identity in the wing. (C) 1994 Academic Press, Inc.