Characterization of SnROP9, a rhoptry protein homologue of Sarcocystis neurona that is expressed in lifecycle stages lacking rhoptry organelles.

Proteins released by the club-shaped, apically located, specialized secretory organelles called rhoptries play an essential role in host cell invasion and intracellular survival of apicomplexans. Sarcocystis neurona, the apicomplexan responsible for equine protozoal myeloencephalitis (EPM), lacks rhoptries in its asexual developmental stages, viz., merozoites and schizonts.