Although multiple determinants for establishing polarity in membranes of epithelial cells have been identified, the mechanism for maintaining the apicobasal polarity is not fully understood. Here, we show that the conserved Hippo kinase pathway plays a role in the maintenance of apicobasal polarity in the developing intestine of Caenorhabditis elegans. We screened suppressors of the mutation in
wts-1, the gene encoding the LATS kinase homolog, whose deficiency leads to the disturbance of the apicobasal polarity of the intestinal cells and the eventual death of organisms. Multiple alleles of
yap-1 and
egl-44, each encoding the worm homologs of YAP/Yki and TEAD/Sd, respectively, were identified as suppressors. WTS-1 directly bound to YAP-1 and inhibited its nuclear accumulation in intestinal cells. We also found that NFM-1, the worm homolog of NF2/Merlin, functioned in the same genetic pathway as WTS-1 to regulate YAP-1 for maintaining cellular polarity. The transcriptome analysis using microarray identified several target candidates of the YAP-1-EGL-44 complex including TAT-2, encoding a putative P-type ATPase. In summary, we have delineated the conserved Hippo pathway in worms consisting of NFM-1-WTS-1-YAP-1-EGL-44 and prove that the proper regulation of YAP-1 by upstream NFM-1 and WTS-1 is esssential for the maintenance of apicobasal membrane identities of the growing intestine