From development to biodiversity--Tribolium castaneum, an insect model organism for short germband development.

Insect embryogenesis is best understood in the fruit fly Drosophila. However, Drosophila embryogenesis shows evolutionary-derived features: anterior patterning is controlled by a highly derived Hox gene bicoid, the body segments form almost simultaneously and appendages develop from imaginal discs. In contrast, embryogenesis of the red flour beetle Tribolium castaneum displays typical features in anterior patterning, axis and limb formation shared with most insects, other arthropods as well as with vertebrates. Anterior patterning depends on the conserved homeobox gene orthodenticle, the main body axis elongates sequentially and limbs grow continuously starting from an appendage bud. Thus, by analysing developmental processes in the beetle at the molecular and cellular level, inferences can be made for similar processes in other arthropods. With the completion of sequencing the Tribolium genome, the door is now open for post-genomic studies such as RNA expression profiling, proteomics and functional genomics to identify beetle-specific gene circuits.