The Evolution of Novelty in Conserved Gene Families

Figure 2

Examples of functional shifts at the level of a single protein. The transcriptional repressor tailless is considered to have a conserved function in bilaterians concerning the patterning of anterior neurons. But in addition to that, it has secondarily acquired a number of lineage-specific functions. In Caenorhabditis elegans, it contributes to the patterning of the vulva in hermaphrodites and in migration of the linker cell from the male gonad. In holometabolous insects, it participates in the patterning of the anterior and posterior tips of the embryo. Strikingly, even if the expression domain of tailless is conserved in holometabolous embryos, this is achieved through highly variable transcriptional pathways (in red on the figure).