Submitted to: Development, Genes and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2008
Publication Date: 4/1/2008
Publication URL: http://hdl.handle.net/10113/14251
Citation: Shippy, T.D., Ronshaugen, M., Cande, J., He, J., Beeman, R.W., Levine, M., Brown, S.J., Denell, R.E. 2008. Analysis of the Tribolium homeotic complex: insights into mechanisms constraining insect Hox clusters. Development, Genes and Evolution. 218(3-4): 127-139. http://dx.doi.org/10.1007/s00427-008-0213-4. Interpretive Summary: Development of the insect embryo is a complex process with many critical steps, disruption of any one of which would lead to the death of the embryo prior to egg-hatch. Although most of the genes required for embryonic survival have been identified, the ways they cooperate to orchestrate normal development are still unclear. This knowledge would enable better design of gene knockout strategies for pest control that target specific regions of vital genes. In this work we show that a large group of development genes in the embryo are grouped into a large cluster on one beetle chromosome, and that this clustering is necessary for their proper functioning, even though each gene in the cluster affects the development of a different region of the embyro. This work refines our ability to design selective toxins for incorporation into resistant crop varieties.
Technical 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.