Multiple regulatory changes contribute to the evolution of the Caenorhabditis lin-48 ovo gene

Recent work points to the importance of changes in gene expression patterns in species-specific differences. Here, we investigate the evolution of the nematode lin-48 ovo gene. lin-48 is expressed in several cells in both Caenorhabditis elegans and Caenorhabditis briggsae, but acts in the excretory duct cell only in C. elegans. We find the differences result both from alterations in the cis-regulatory sequences and in proteins that mediate lin-48 expression. One factor that contributes to the species differences is the bZip protein CES-2. Our results indicate the accumulation of several regulatory changes affecting one gene can contribute to evolutionary change.