Synthesis of extracellular sulfated molecules requires active 3'-phosphoadenosine 5'-phosphosulfate (PAPS). For sulfation to occur, PAPS must pass through the Golgi membrane, which is facilitated by Golgi-resident PAPS transporters. Caenorhabditis elegans PAPS transporters are encoded by two genes,
pst-1 and
pst-2. Using the yeast heterologous expression system, we characterized PST-1 and PST-2 as PAPS transporters. We created deletion mutants to study the importance of PAPS transporter activity. The
pst-1 deletion mutant exhibited defects in cuticle formation, post-embryonic seam cell development, vulval morphogenesis, cell migration, and embryogenesis. The
pst-2 mutant exhibited a wild-type phenotype. The defects observed in the
pst-1 mutant could be rescued by transgenic expression of
pst-1 and hPAPST1 but not
pst-2 or hPAPST2. Moreover, the phenotype of a
pst-1;
pst-2 double mutant were similar to those of the
pst-1 single mutant, except that larval cuticle formation was more severely defected. Disaccharide analysis revealed that heparan sulfate from these mutants was undersulfated. Gene expression reporter analysis revealed that these PAPS transporters exhibited different tissue distributions and subcellular localizations. These data suggest that
pst-1 and
pst-2 play different physiological roles in heparan sulfate modification and development.