IFA of pH 8.1 treated Δcst1::cst1 in vitro cysts demonstrated that the strain complemented with full-length cDNA of CST1 has the correct localization of CST1 to the cyst wall, as well as the restoration of DBA staining (Figure 4C) and mAb 73.18 staining (Figure 5B) of the cyst wall. This evidence concerns the gene CST1 and cyst.