The molecular genetics of the bithorax complex of Drosophila: cis-regulation in the Abdominal-B domain.
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.
Celniker
S E
SE
Division of Biology, California Institute of Technology, Pasadena 91125.
Sharma
S
S
Keelan
D J
DJ
Lewis
E B
EB
D000005:Abdomen; D000818:Animals; D002875:Chromosomes / Q000378:metabolism; D004330:Drosophila / Q000196:embryology / Q000235:genetics*; D029721:Drosophila Proteins; D005786:Gene Expression Regulation; D006257:Head; D018398:Homeodomain Proteins; D006720:Homozygote; D007301:Insect Hormones / Q000096:biosynthesis / Q000235:genetics*; D008297:Male; D009154:Mutation; D012045:Regulatory Sequences, Nucleic Acid
C062393:Abd-B proteins, Drosophila; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D007301:Insect Hormones