title: Analysis of the Tribolium homeotic complex: insights into mechanisms constraining insect Hox clusters.
abstract: The remarkable conservation of Hox clusters is an accepted but little understood principle of biology. Some organizational constraints have been identified for vertebrate Hox clusters, but most of these are thought to be recent innovations that may not apply to other organisms. Ironically, many model organisms have disrupted Hox clusters and may not be well-suited for studies of structural constraints. In contrast, the red flour beetle, Tribolium castaneum, which has a long history in Hox gene research, is thought to have a more ancestral-type Hox cluster organization. Here, we demonstrate that the Tribolium homeotic complex (HOMC) is indeed intact, with the individual Hox genes in the expected colinear arrangement and transcribed from the same strand. There is no evidence that the cluster has been invaded by non-Hox protein-coding genes, although expressed sequence tag and genome tiling data suggest that noncoding transcripts are prevalent. Finally, our analysis of several mutations affecting the Tribolium HOMC suggests that intermingling of enhancer elements with neighboring transcription units may constrain the structure of at least one region of the Tribolium cluster. This work lays a foundation for future studies of the Tribolium HOMC that may provide insights into the reasons for Hox cluster conservation.
authors.affiliation: Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, USA. tshippy@ksu.edu
authors.forename: Teresa D
authors.initials: TD
authors.lastname: Shippy
authors.forename: Matthew
authors.initials: M
authors.lastname: Ronshaugen
authors.forename: Jessica
authors.initials: J
authors.lastname: Cande
authors.forename: Jianping
authors.initials: J
authors.lastname: He
authors.forename: Richard W
authors.initials: RW
authors.lastname: Beeman
authors.forename: Michael
authors.initials: M
authors.lastname: Levine
authors.forename: Susan J
authors.initials: SJ
authors.lastname: Brown
authors.forename: Robin E
authors.initials: RE
authors.lastname: Denell
mesh_terms: D000818:Animals; D017124:Conserved Sequence; D004625:Embryo, Nonmammalian; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D017344:Genes, Insect; D049810:Genetic Speciation; D018398:Homeodomain Proteins / Q000235:genetics; D019476:Insect Proteins / Q000235:genetics; D005810:Multigene Family; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D014231:Tribolium / Q000196:embryology / Q000235:genetics*
chemical_list: D018398:Homeodomain Proteins; D019476:Insect Proteins; C435186:Scr protein, Tribolium castaneum; C424265:maxillopedia protein, Tribolium