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Title: TRIBOLIUM HOX GENES REPRESS ANTENNAL DEVELOPMENT IN THE GNATHOS AND TRUNK

Author
item BROWN, SUSAN - KANSAS STATE UNIVERSITY
item SHIPPY, TERESA - KANSAS STATE UNIVERSITY
item Beeman, Richard
item DENELL, ROBIN - KANSAS STATE UNIVERSITY

Submitted to: Molecular Phylogenetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2002
Publication Date: 9/30/2002
Citation: BROWN, S.J., SHIPPY, T.D., BEEMAN, R.W., DENELL, R.E. TRIBOLIUM HOX GENES REPRESS ANTENNAL DEVELOPMENT IN THE GNATHOS AND TRUNK. MOLECULAR PHYLOGENETICS AND EVOLUTION 24: 384-387. 2002.

Interpretive Summary: Steady advances in genetic analysis of insect development have revealed that the complex many-celled embryo develops from a single-celled egg through the action of several different sets of genes that act in progressive waves. The first set of genes determines which end of the egg is which (head and tail) and also which sides are top and bottom (dorsal and ventral). Then a second set of genes divides the embryo into many bod segments similar to links in a chain. Next, a still different set of genes stimulates all segments to begin to grow buds that will later develop into legs, antennae, mandibles or other appendages. Next, a set of genes begins to confer antennal identity on all segment buds, even those destined to become legs. Finally, a set of genes called "Hox" genes, switches the generalized "antennal" identify to the correct appendage appropriate for each segment (head, thorax or abdomen). These genes work differently in each of the various insect groups. This research shows how insect development genes are specific for different kinds of insects, suggesting that we can design inhibitors that are specific for particular species.

Technical Abstract: Hox genes encode transcription factors that regulate developmental fate along the anterior-posterior body axis of metazoans. Hox genes accomplish this regulation by activating some genes while suppressing others. Using a combination of mutagenesis and RNA inhibition (RNAi), and taking advantage of the sophisticated genetics possible with Tribolium castaneum, we showed that in this species, Hox genes control posterior differentiation in part by suppressing antennal development, and that antennal identity is the default pathway for all body segments in the absence of Hox gene function. However, other genes including homothorax, spineless and extradenticle are required for antennal differentiation, both in the normal antennae and in more posterior segments lacking Hox gene function. Thus, there must be a more basic ground state underlying the antennal default state. This more basic ground state would be expressed in the complete absence of all genes that have any effect on segment differentiation. Preliminary evidence from Drosophila suggests that this ground state might be leg-like, but additional experiments involving multiple gene knockout will be required to more clearly resolve this question.