A group of genes controlling the spatial expression of the bithorax complex in Drosophila

Abstract

The morphological diversity among the body segments of Drosophila, as displayed in the pattern of the larval cuticle1, arises during embryogenesis by the selective expression of homoeotic genes. For example, the bithorax complex (BX-C) confers abdominal development on the segments in the posterior half of the embryo which otherwise would develop into thoracic segments2. Mutations in trans-regulatory genes such as Polycomb (Pc)2 or extra sex combs (esc)3 cause indiscriminate expression of the BX-C genes, which leads to all body segments being abdominal. I report here on mutations in four other trans-regulatory genes, members of a novel class of more than 20 genes controlling the spatial expression of BX-C genes. In contrast to Pc and esc mutations, only partial transformation into posterior abdominal development is observed in mutant embryos. However, embryos mutant for two or more of these genes show strong homoeotic transformation of all body segments similar to, or stronger than, that seen in Pc and esc embryos, indicating that these genes act synergistically in normal development to control the spatial expression of the BX-C genes. © 1985 Nature Publishing Group.