cis-Regulatory Control of Three Cell Fate-Specific Genes in Vulval Organogenesis of C. elegans and C. briggsae

The great-grandprogeny of the Caenorhabditis elegans vulval precursor cells (VPCs) adopt one of the final vulA, B1, B2, C, D, E and F cell types in a precise spatial pattern. Formation of the pattern of vulval cell types is likely to depend upon the cis-regulatory regions of the transcriptional targets of these intercellular signals in vulval development. The outcome of such differential activation will result in individual cell types. egl-17, zmp-1, cdh-3 are expressed differentially in the developing vulva cells, providing a potential readout for different signaling pathways. To understand how different signaling pathways interact to specify unique vulval cell types in a precise pattern, I have identified upstream cis-regulatory regions that are sufficient for their ability to confer vulval cell type-specific regulation when fused in cis to the basal pes-10 promoter. In the egl-17 promoter, I have identified a 143 base pair (bp) region that drives vulC and vulD expression, and a 102 bp region that is sufficient to drive the early expression in presumptive vulE and vulF cells. In the zmp-1 promoter, I have identified a 300 bp region that is sufficient to drive expression in vulE, vulA and the anchor cell. In the cdh-3 promoter, I have identified a 689 bp region sufficient to drive expression in the anchor cell and vulE, vulF, vulD and vulC, a 155 bp region sufficient to drive only anchor cell expression, and a separate 563 bp region that was also sufficient to drive expression in these vulval cells. I have identified the C. briggsae homologs of these three genes, and the corresponding control regions, and tested these regions in both C. elegans and C. briggsae. I find that these regions of similarity in C. elegans and C. briggsae upstream of egl-17, zmp-1, and cdh-3 promote expression in vulval cells and the anchor cell. Using