Subunit of the V0 complex of vacuolar(H+)-ATPase (V-ATPase), a multisubunit enzyme composed of a peripheral complex (V1) that hydrolyzes ATP and a membrane integral complex (V0) that translocates protons (By similarity). V-ATPase is responsible for acidifying and maintaining the pH of intracellular compartments and in some cell types, is targeted to the plasma membrane, where it is responsible for acidifying the extracellular environment (By similarity). During embryonic development, the V-ATPase is required to repress fusion of epidermal cells probably by negatively regulating eff-1-mediated cell fusion (PubMed:15866168). V-ATPase is a heteromultimeric enzyme made up of two complexes: the ATP-hydrolytic V1 complex and the proton translocation V0 complex. The V1 complex consists of three catalytic AB heterodimers that form a heterohexamer, three peripheral stalks each consisting of EG heterodimers, one central rotor including subunits D and F, and the regulatory subunits C and H. The proton translocation complex V0 consists of the proton transport subunit a, a ring of proteolipid subunits c9c'', rotary subunit d, subunits e and f, and the accessory subunits vah-19/Ac45 and vah-20/PRR. In late stage embryos, localizes to the apical cell membrane and partially to apical junctions of epidermal cells (PubMed:15866168). In the gut of 1.5-fold embryo, localizes to puctate structures (PubMed:15866168). In the 1.5-fold embryo, expressed in gut cells but not in epidermal cells (at protein level) (PubMed:15866168). In the 3-fold embryo, expressed in dorsal and ventral epidermal cells, but not in seam cells, and in the excretory cell (at protein level) (PubMed:15866168). RNAi-mediated knockdown causes hyperfusion of epidermal cells in embryos. Belongs to the V-ATPase e1/e2 subunit family.