DIVERSIFICATION OF ARTHROPOD HOX GENES AS A PARADIGM FOR THE EVOLUTION OF GENE FUNCTIONS

Hox genes are highly conserved throughout the metazoans in both sequen ce, chromosomal arrangement, and function. Yet within the arthropods t hese genes have undergone considerable diversification. We examine anc estral and novel functions of arthropod Hox genes in an attempt to und erstand how these functions might evolve. We suggest that functional d iversification of Hox genes begins with the acquisition of multiple di stinct cis-regulatory elements responsible for different aspects of th eir gene expression. Gene duplication may serve to dissociate the func tional-selective constraints associated with each of these regulatory elements and to allow divergence of the corresponding coding sequences .