FIGURE 1: GCaMP6s is expressed in the cytosol of intracellular tachyzoites. (A) Images illustrating co-staining of EGFP (GCaMP6s) with the markers for cytosol (TgHsp90) or inner membrane complex (TgGap45). Stable transgenic parasites of the parental (RHΔku80-hxgprt-) and PTS mutant (Δtgpts) strains, expressing GCaMP6s under the control of the TgGRA1 promoter, were generated by negative selection with FUDR (targeting the UPRT locus). Intracellular tachyzoites (MOI, 1; 24 h infection) were imaged following the immunofluorescence assay using the indicated antibodies. No cross-fluorescence (bleeding effect) was observed across the two color channels. (B) A representative immunoblot confirming the expression of intact M13-CpEGFP-CaM fusion protein (a.k.a. GCaMP6s or GECI) in the parental and PTS knockout strains. TgHsp90 was used as the loading control.