Three-dimensional ultrastructure of Plasmodium falciparum throughout cytokinesis

Abstract

New techniques for obtaining electron microscopy data through the cell volume are being increasingly utilized to answer cell biologic questions. Here, we present a three-dimensional atlas of Plasmodium falciparum ultrastructure throughout parasite cell division. Multiple wild type schizonts at different stages of segmentation, or budding, were imaged and rendered, and the 3D structure of their organelles and daughter cells are shown. Our high-resolution volume electron microscopy both confirms previously described features in 3D and adds new layers to our understanding of Plasmodium nuclear division. Interestingly, we demonstrate asynchrony of the final nuclear division, a process that had previously been reported as synchronous. Use of volume electron microscopy techniques for biological imaging is gaining prominence, and there is much we can learn from applying them to answer questions about Plasmodium cell biology. We provide this resource to encourage readers to consider adding these techniques to their cell biology toolbox.

Plasmodium berghei Kinesin-5 Associates With the Spindle Apparatus During Cell Division and Is Important for Efficient Production of Infectious Sporozoites

“…The first type of mitosis occurs during asexual proliferation, with multiple asynchronous nuclear divisions producing up to 32 nuclei (during schizogony in the blood of the vertebrate host) or more than 1,000 nuclei (during schizogony in the liver of the vertebrate host and sporogony in the mosquito gut), with cytokinesis occurring only after nuclear division is complete, to produce haploid progeny cells ( Sinden et al., 1976 ; Sinden, 1991 ; Gerald et al., 2011 ; Francia and Striepen, 2014 ). It is important to note that the final round of nuclear division is asynchronous, in contrast to what was thought previously ( Rudlaff et al., 2020 ). The second type of mitosis is during male gametogony (part of the sexual stage in the mosquito gut) where there are three rapid rounds of DNA replication from 1N to 8N within 10 to 15 min, followed by karyokinesis and cytokinesis to produce eight flagellate haploid male gametes ( Sinden et al., 1976 ; Zeeshan et al., 2019a ).…”

“…A very low and diffuse expression of kinesin-5 throughout the cytoplasm was observed in older trophozoites, a stage similar to G1 phase in higher eukaryotes ( Arnot and Gull, 1998 ; Arnot et al., 2011 ) when preparation for DNA replication begins. Late trophozoites mark the transition into early S phase when DNA synthesis starts ( Arnot et al., 2011 ) and schizogony is marked by the presence of three or more nuclei ( Rudlaff et al., 2020 ). Kinesin-5 was observed as strong foci adjacent to the Hoechst-stained DNA in early schizonts when nuclear division had commenced, and representing the first M phase of the cell cycle ( Arnot and Gull, 1998 ; Arnot et al., 2011 ) ( Figure 2A ).…”

Dispensable Role of Mitochondrial Fission Protein 1 (Fis1) in the Erythrocytic Development of Plasmodium falciparum

“…Unlike many cells that divide via binary fission, the malaria parasite replicates its nuclear DNA for 3 to 5 rounds without concurrent cytokinesis, resulting in the formation of 8 to 32 daughter cells (merozoites). This unique mechanism of division starts at the very end of the asexual life cycle and is termed schizogony (2). In mosquito and liver stages, the parasite's nuclear DNA undergoes 13 to 14 rounds of replication without cytokinesis, producing up to 10,000 progeny all at once (3); this process is termed sporogony in the mosquito and exoerythrocytic schizogony in the liver.…”

Rapid kinetics of lipid second messengers controlled by a cGMP signalling network coordinates apical complex functions inToxoplasmatachyzoites

“…Curiously, DGK2 is absent in Plasmodium, and this may indicate differences in its egress regulation compared to Toxoplasma (Figure S11). The major difference between the acute asexual stages of the two parasites is that Plasmodium asexual blood stages must undergo a developmental change into a motile zoite prior to egress in order to escape (Wang et al 2020;Absalon et al 2018;Rudlaff et al 2020). It might be that Plasmodium has lost DGK2 because there is no requirement to signal to rings or trophozoites that have not yet developed into invasion-ready merozoites so instead Plasmodium possibly relies on internal metabolic cues for egress.…”