Specifically required in the formation and maintenance of the conoid fibers; the conoid is a component of the cytoskeletal apical complex, which is composed of a left-handed spiral of 14 fibers made from a nontubular tubulin polymer (PubMed:27932494). Promotes the organization, curvature, and stability of the conoid fibers, and probably bridges other conoid components to the tubulin core (PubMed:27932494, PubMed:32111164). Localizes along the tubulin-containing conoid fibers; the conoid is a component of the cytoskeletal apical complex, which is composed of a left-handed spiral of 14 fibers made from a nontubular tubulin polymer (PubMed:27932494, PubMed:32111164). During early daughter development, localizes to the center of a five-petaled flower-like tubulin structure in the nascent daughter apical cytoskeleton (PubMed:27932494). Expressed in tachyzoites (at protein level). The doublecortin is involved in the binding to microtubules; however, it is not sufficient by itself and requires the partial p25alpha domain. The partial p25 alpha domain binds to microtubules. Reduced tachyzoite growth and host invasion (PubMed:27932494). Loss of tubulin at the apical complex (PubMed:27932494). Abnormal conoid morphology characterized by a shorter and less rectangular structure a weaker or absent basket-weave stripe pattern (PubMed:27932494). Cortical microtubules, the mitotic spindle, spindle pole, and centrioles are normal (PubMed:27932494).