Upper panel: Asymmetric organization of organelles confers a lateral polarity in P. falciparum merozoites. Staining with antibodies against different subcellular organelle markers is shown in the left-hand column. (A) a-Tubulin antibodies staining the merozoite subpellicular microtubules. (B) Bip, an ER marker. (C) ERD2, a cis-Golgi marker. (D) ACP, an apicoplast marker. (E) Cytochrome c, a mitochondrial marker. Corresponding costaining with rat anti-HA mAb 3F10 (A and C–E) or mouse anti-HA mAb 2C16 (B) together with nuclear staining with DAPI (blue) and an overlay of all channels is shown in subsequent columns. The right-hand column shows a digital zoom of merozoites showing that the red and green staining occurs on the same side of the nucleus. (Scale bar, 1 mm.) HA-PfROM1 was observed to be localized in close proximity to longitudinal subpellicular microtubules of the merozoite.

Lower panel: HA-PfROM1 is secreted on the merozoite surface and concentrates at the posterior pole of the merozoite. Staining of free merozoites with antibodies against a micronemal marker (A) or with a rhoptry marker at the apical end (B) is shown in the left-hand column (red). Corresponding costaining with rat anti-HA mAb 3F10 (green) together with the overlay between the red and green channels is shown in subsequent columns. The right-hand column shows the corresponding DIC image. Arrow heads point to the merozoite posterior pole. (Scale bar, 1 mm.)

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. Copyright 2009 National Academy of Sciences, U.S.A.