The molecular genetics of the bithorax complex of Drosophila: cis-regulation in the Abdominal-B domain

EMBO J. 1990 Dec;9(13):4277-86.


In Drosophila the Abdominal-B (Abd-B) domain of the bithorax complex (BX-C) spans over 100 kb and is responsible for specifying the identities of adult abdominal segments five (A5) to nine (A9), inclusive, and correspondingly, neuromeres 10-14 of the embryonic central nervous system. The domain consists of a region coding for two proteins, ABD-BI (54 kd) and ABD-BII (36 kd) and cis-regulatory regions extending from infra-abdominal-5 (iab-5) to iab-9, inclusive. We have used a monoclonal anti-ABD-B antibody to infer that mutants in iab-8 eliminate the expression of ABD-BI in neuromeres 10-13, inclusive, and that mutants in iab-9 eliminate expression of ABD-BII in neuromere 14. ABD-B expression is also analyzed in homozygotes for (i) loss-of-function mutants involving the iab-5, iab-6 and iab-7 regions, (ii) gain-of-function mutants Miscadastral pigmentation (Mcp) and Superabdominal (Sab), and (iii) a trans-regulator, Polycomb (Pc). ABD-B expression along the antero-posterior axis is colinear with the chromosomal order of the cis-regulatory regions. The behavior of rearrangement-associated iab-6 and iab-7 mutants suggests that the enhancer-like region, iab-5, and possibly also iab-6, may be shared between the abd-A and Abd-B domains. Such sharing is proposed as a factor that tends to keep gene complexes intact during evolution.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Abdomen*
  • Animals
  • Chromosomes / metabolism
  • Drosophila / embryology
  • Drosophila / genetics*
  • Drosophila Proteins*
  • Gene Expression Regulation
  • Head*
  • Homeodomain Proteins*
  • Homozygote
  • Insect Hormones / biosynthesis
  • Insect Hormones / genetics*
  • Male
  • Mutation
  • Regulatory Sequences, Nucleic Acid*


  • Abd-B proteins, Drosophila
  • Drosophila Proteins
  • Homeodomain Proteins
  • Insect Hormones