Submitted to: Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/4/2006
Publication Date: 9/1/2006
Publication URL: http://hdl.handle.net/10113/28710
Citation: Shippy, T.D., Rogers, C.D., Beeman, R.W., Brown, S.J., Denell, R.E. 2006. The Tribolium castaneum ortholog of Sex combs reduced controls dorsal ridge development. Genetics. 174(1): 297-307. http://dx.doi.org/10.1534/genetics.106.0.58610. 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 many or even most of the genes required for embryonic survival have been identified, the specific functions of regions within each gene are unknown. This knowledge would enable better design of gene knockout strategies for pest control that target specific regions of vital genes. In this work we identified subregions of the “Cephalothorax” gene required for development of the insect head, and showed that each subregion has a unique and essential effect during embryonic growth. This work refines our ability to design selective toxins for incorporation into resistant crop varieties.
Technical Abstract: In insects, the boundary between the embryonic head and thorax is formed by the dorsal ridge, a fused structure composed of portions of the maxillary and labial segments. However, the mechanisms that promote development of this unusual structure remain a mystery. In Drosophila, mutations in the Hox genes Sex combs reduced and Deformed have been reported to cause abnormal dorsal ridge formation, but the significance of these abnormalities is not clear. We have identified three mutant allele classes of Cephalothorax, the Tribolium castaneum (red flour beetle) ortholog of Sex combs reduced, each of which has a different effect on dorsal ridge development. By using Engrailed expression to monitor dorsal ridge development in these mutants, we demonstrate that Cephalothorax promotes the fusion and subsequent dorsolateral extension of the maxillary and labial Engrailed stripes (posterior compartments) during dorsal ridge formation. Molecular and genetic analysis of these alleles indicates that the N terminus of Cephalothorax is important for the fusion step, but is dispensable for Engrailed stripe extension. Thus, we find that specific regions of Cephalothorax are required for discrete steps in dorsal ridge formation.