AP2V-2 Is Required for Tachyzoite Proliferation in Toxoplasma gondii

Toxoplasma gondii undergoes multiple developmental transitions during its complex life cycle, which are controlled by coordinated transcriptional and epigenetic regulation. The MORC/HDAC3/ApiAP2 complex has been implicated in the repression of merozoite- and sexual-stage genes in tachyzoites. AP2V-2 (TGGT1_285895) was previously identified as a component associated with this regulatory network, but its biological function remains poorly understood. Here, we characterized AP2V-2 using conditional protein depletion combined with phenotypic, transcriptomic, and genome-wide occupancy analyses. AP2V-2 localized to the parasite nucleus and was detected throughout the tachyzoite cell cycle. Conditional depletion of AP2V-2 markedly impaired plaque formation and intracellular replication but had little effect on parasite invasion. The replication defect was reversible after removal of indole-3-acetic acid. RNA sequencing identified 211 differentially expressed genes after AP2V-2 depletion. Of these, 79.6% overlapped with genes dysregulated after MORC depletion, with particularly strong overlap among upregulated genes. In contrast, CUT&Tag identified only 45 AP2V-2-associated peaks, most of which were located in intergenic regions. Although a subset of enteroepithelial-stage genes was upregulated after AP2V-2 depletion, AP2V-2 did not occupy their promoter regions, typical merozoite markers were not induced, and no endopolygeny-like division was observed. These findings indicate that AP2V-2 is required for normal tachyzoite replication but differs functionally from the ApiAP2 factors that directly control merozoite developmental programs.