MOLECULAR ANALYSIS OF THE DELETION MUTANTS IN THE E-HOMEOTIC COMPLEX OF THE SILKWORM BOMBYX-MORI

The E loci in Bombyx mori are expected to contain a homeotic gene comp lex specifying the identities of the larval abdominal segments. Howeve r, the molecular structure of this complex remains to be determined. W e have started to analyze the structural changes in the E complex muta tions. We used three newly isolated Bombyx homeobox genes as probes. T hese genes are probably homologues of the Ultrabithorax (Ubx), abdomin al-A (abd-A) and Abdominal-B (Abd-B) in the Drosophila bithorax comple x, because the amino-acid sequences of the homeobox regions in these B ombyx genes are almost identical to those of Drosophila genes. We foun d that the Bombyx Ubx and abd-A genes are deleted in the E(N) chromoso me, and the Bombyx abd-A gene is deleted in the E(Ca) chromosome. From these results, we conclude that the Bombyx E complex consists of the Ubx, abd-A and possibly Abd-B genes, which may play similar roles to t heir homologues in the Drosophila bithorax complex.