Anti-HA antibodies specifically recognize the HA-PfROM1 protein in transgenic HA-PfROM1 3D7 parasites. (B) IFA analysis of HA-PfROM1 in a developing schizont (4 nuclei stage). (C) Merozoites in a segmenter probed with anti-HA rat mAb 3F10 (green) and the nuclear stain (blue, Upper) or with anti-AMA1 (red, Lower). Note in the individual merozoites anti-HA mAb staining appears to be localized on one side of the nucleus, with characteristic bulbous region (arrowheads) that is toward the apical end of the merozoites. The stalk region runs along one side of the nucleus. PfROM1 was not found associated with micronemes, rhoptries, or dense granules, the three identified secretory organelles of invasion. Release of merozoites from schizonts resulted in the movement of PfROM1 from the lateral asymmetric localization to the merozoite apical pole and the posterior pole. We have named this single thread-like organelle in merozoites, the mononeme.

Singh S, Plassmeyer M, Gaur D, Miller LH. Mononeme: a new secretory organelle in Plasmodium falciparum merozoites identified by localization of rhomboid-1 protease. Proc Natl Acad Sci U S A. 2007 104:20043-8