Abstract
Commitments to developmental pathways are often made and maintained in groups of cells. Such commitments are conferred by the products of selector genes, many of which are homeobox genes. Homeobox genes can maintain their expression by directly autoregulating their own transcription. Here, we report a case where positive autoregulation of Ultrabithorax, a homeotic Drosophila gene, is at least partly indirect and mediated by the extracellular signal molecules that are products of the genes wingless and decapentaplegic. Indirect autoregulatory mechanisms may be used to ensure coordinate maintenance of selector gene activity in groups of cells.
