An analysis of semaphorin-mediated cellular interactions in theC. elegansepidermis using the IR-LEGO single-cell gene induction system

One of the major functions of the semaphorin signaling system is the regulation of cell shape. In the nematode C. elegans , membrane-bound semaphorins SMP-1/2 (SMPs) regulate the morphology of epidermal cells via their receptor plexin, PLX-1. In the larval male tail of the SMPs/PLX-1 signaling mutants, the border between two epidermal cells, R1.p and R2.p, is displaced anteriorly, resulting in the anterior displacement of the anterior most ray, ray 1, in the adult male. To elucidate how the intercellular signaling mediated by SMPs regulates the position of the intercellular border, we performed mosaic gene expression analyses by using IR-LEGO (Infra R ed L aser E voked G ene O perator). We show that PLX-1 expressed in R1.p and SMP-1 expressed in R2.p is required for proper positioning of ray 1. The result suggests that SMPs signaling promotes extension, rather than retraction, of R1.p. This is in contrast to a previous finding that SMPs mediate inhibition of cell-extension of vulval precursor cells, another group of epidermal cells of C. elegans, indicating the context-dependence of cell shape control via the semaphorin signaling system.