Growth of Hsp90 knockout parasite (ΔHsp90) in vitro. The parasites were cultured in African green monkey kidney (Vero) cells, 10⁵ T. gondii were added to the 6-well plates, and the infection ratio was 1:1. Observation of RHΔku80 (A), ΔHsp90 (B), and complemented (C) parasites by inverted microscope. The plaque produced by ΔPKAR strains (Fig. 6B) was significantly smaller than that of RHΔku80 and complemented parasites (Figs. 6A, 6C), scale bar = 20 μm. T. gondii tachyzoites and Vero cells were indicated by arrows, T. gondii (black arrow), Vero cells (white arrow). (D) The parasites were collected at the same time, and genomic DNA was extracted by TIANGEN kit. T. gondii DNA was detected by SYBR-green real-time PCR using B1 primer pairs, the standard curve was obtained by the known concentration of the RHΔku80 parasites with the primers (B1), and the parasite number was calculated by interpolation from this standard curve. **p < 0.01, ***p < 0.001.