Homoeosis in Drosophila: The Lethal Syndrome of the Regulator of bithorax (or trithorax) Locus and Its Interaction With Other Homoeotic Loci

摘要

Regulator of bithorax ( Rg-bx )- [or trithorax ( trx )-] lethal zygotes show anterior transformations of various cuticular features of the larval thorax and abdomen. The Rg-bx - lethal syndrome depends on the dosage of the bithorax gene complex (BX-C), and lack of Rg-bx+ function is antagonistic to posterior transformations displayed by Polycomb ( Pc )- embryos. Significantly, when the BX-C is deleted, the Rg-bx - embryos disclose homoeosis of mesothoracic to prothoracic cuticular structures. This homoeotic transformation is due to a reduction in Antennapedia ( Antp )+ gene activity and is consequently dependent on the dosage of the Antennapedia gene complex (ANT-C), suggesting that the Rg-bx + activity is necessary for proper expression of the Antp + gene. However, the functional relationship between the Rg-bx and Sex combs reduced ( Scr ) loci in embryogenesis is still to be established.