Figure 4.

Immunogold labeling of YFP-tagged RNG1 with electron microscopy illustrates that RNG1 is found in the apical region of Toxoplasma tachyzoites (a-g). (a) Gold labeling is located in a discrete region of the cytosolic face of the parasite pellicle in the apical region. The label lies beneath extended conoids (co) whether the section is grazing so that conoid filaments are visible (arrows, b) or through the conoid, such that the terminal portion of the IMC is visible (arrow, c). Panel d illustrates that gold is restricted to the region adjacent to the conoid (co), above the micronemes (mn) and interior to the plasma membrane (pm) and inner membrane complex (imc). In samples where sections bisect individual conoid filaments (arrows, e and f), RNG1 labeling is between the base of the conoid and the IMC. In a grazing section of the APR, this structure appears as a dark semicircle (g, arrows) and shows labeling along its entire length. Scale bar in panel c = 200 nm.