Novel cell-cell interactions during vulva development in Pristionchus pacificus

Vulva development differs between Caenorhabditis elegans and Pristionchus p acificus in several ways, Seven of 12 ventral epidermal cells in P, pacific us die of apoptosis, whereas homologous cells in C, elegans fuse with the h ypodermal syncytium, Vulva induction is a one-step process in C, elegans, b ut requires a continuous interaction between the gonad and the epidermis in P. pacificus. Here we describe several novel cell-cell interactions in P. pacificus, focusing on the vulva precursor cell P8.p and the mesoblast M, P 8,p in P. pacificus, unlike its homologous cell in C. elegans, is incompete nt to respond to gonadal signaling in the absence of other vulva precursor cells, but can respond to lateral signaling from a neighboring vulval precu rsor. P8,p provides an inhibitory signal that determines the developmental competence of P(5,7),p, This lateral inhibition acts via the mesoblast M an d is regulated by the homeotic gene Ppa-mab-5, In Ppa-mab-5 mutants, M is m isspecified and provides inductive signaling to the vulval precursor cells, including P8,p, Taken together, vulva development in P, pacificus displays novel cell-cell interactions involving the mesoblast M and P8,p, In partic ular, P8,p represents a new ventral epidermal cell type, which is character ized by novel interactions and a specific response to gonadal signaling.