Biology subjects

Holder, A. A.

Publications and source records attributed to Holder, A. A..

At least 19 recordsLinked to original sources

bioRxiv2026

Plasmodium rootlet SFA1 coordinates cell replication, apical polarity and cytoskeletal organisation during sexual development

Rootlet fibres are evolutionarily conserved cytoskeletal structures involved in basal body positioning and cytoskeletal organisation in diverse eukaryotes. Plasmodium spps, undergo complex developmental transitions that require precise coordination of cell polarity, cytoskeletal remodelling and nuclear division. In Plasmodium striated fibre assemblin1 (SFA1) and SFA2 have been implicated in linking the centriolar plaque to nascent apical poles during schizogony and sporogony. However, their role in sexual development is unclear. Here we show SFA1 is absent from the male basal body but is present in female gametocytes, where it marks the polarity initiation site during zygote-to-ookinete differentiation. We also identify associations between SFA1, SFA2 and pellicle-associated proteins. Loss of sfa1 disrupts apical polarity, pellicle organisation and subpellicular microtubules, producing abnormal immotile ookinetes and affecting further sporozoite development, leading to complete loss of parasite transmission. Together, these findings support an important role for SFA1 in organising the cytoskeletal architecture required for malaria transmission.

cell biology↗

bioRxiv2026

Plasmodium Protein Kinase 2 is required for ookinete to oocyst transition, and parasite transmission by the mosquito.

Plasmodium spp., the parasites that are the causative agents of malaria, encode a repertoire of divergent protein kinases that coordinate essential processes including cell division and host cell invasion, yet the functions of many kinases are poorly defined. Plasmodium Protein Kinase 2 (PK2) is essential for asexual blood-stage proliferation and has been implicated in P. falciparum merozoite invasion of red blood cells. However, its role in the sexual stages of the Plasmodium life cycle responsible for transmission is unknown. Here, using live cell imaging, functional analyses, ultrastructure microscopy and phosphoproteomics, we demonstrate that PK2 has a significant role in the Plasmodium berghei life cycle in the mosquito. We show that PK2 is expressed in merozoites, ookinetes and sporozoites - the invasive stages of the parasite life cycle. A conditional knockdown approach revealed that PK2 is required for the ookinete to oocyst transition in the mosquito midgut, potentially associated with altered microneme positioning. Using haemocoel injection to bypass the midgut barrier revealed that PK2 is also required for sporozoite development after midgut invasion. Following PK2 knockdown, global proteome abundance was largely unaffected at 24 h post activation, whereas phosphoproteomics identified changes in phosphorylation of proteins linked to midgut traversal, parasite architecture, and gene regulation. These studies provide insight into the importance of PK2 function in Plasmodium sexual stages and parasite transmission through the mosquito, highlighting its essential function during the three invasive stages of the parasites life cycle.

microbiology↗

bioRxiv2025

A divergent Plasmodium NEK4 acts as a key regulator driving the early events of meiosis

Meiosis is a conserved yet evolutionarily varied process underpinning sexual reproduction in eukaryotes. In the malaria parasite Plasmodium, meiosis is unconventional: it occurs immediately after fertilisation (post-zygotic) and must be coordinated with the transformation of the zygote into a motile ookinete. The mechanisms synchronising these meiotic and morphogenetic programmes remain unknown. Here, we identify the Plasmodium berghei NIMA-related kinase NEK4 as a key regulator that couples meiotic initiation with zygote morphogenesis. Using ultrastructure expansion microscopy, we show that NEK4 accumulates at the microtubule-organising centre (MTOC) and the apical polar complex (APC) shortly after fertilisation, preceding the assembly of perinuclear and cortical microtubules. We reveal that Plasmodium zygotes undergo MTOC-associated nuclear migration, analogous to the meiotic nuclear movement in fission yeast. Deletion of the Pbnek4 gene results in complete developmental arrest: MTOC duplication and microtubule formation are blocked, chromatin remains uncondensed, and nuclear migration and cell polarity fail to establish. Transcriptomic and phosphoproteomic analyses reveal that absence of NEK4 causes a collapse in transcriptional and phosphoregulatory networks governing meiosis and cytoskeletal organisation, leading to reduced expression and phosphorylation of important players, including HOP1, REC8, and AP2-O. These findings establish NEK4 as a key regulator driving meiotic entry and zygote maturation.

microbiology↗

bioRxiv2025

Apicortin defines the Plasmodium apical conoid body during transmission but is dispensable for the parasite life cycle

Apicomplexan parasites such as Plasmodium spp. and Toxoplasma gondii possess unique tubulin-based structures, including subpellicular microtubules and apical polar rings, which are essential for parasite motility, host cell invasion, and replication. How the stability of these structures is maintained is poorly understood, but it may involve Apicortin, a microtubule-associated protein, so-far found only in apicomplexans and the placozoan Trichoplax adhaerens. Apicortin contains a doublecortin (DC) domain and a partial tubulin polymerisation-promoting protein (TPPP) domain, both implicated in microtubule binding and stabilization. In this study, we investigated the location and function of Apicortin in Plasmodium berghei. Live cell imaging of a transgenic parasite line expressing GFP-tagged Apicortin showed that it was present at the apical end of invasive parasites only during development of transmission stages within the mosquito vector. High-resolution imaging using super-resolution and expansion microscopy, revealed that Apicortin forms a distinct ring-like structure in the apical complex region at the apical end of ookinetes and sporozoites. However, deletion of the Apicortin gene had no effect on parasite development and transmission through the mosquito, indicating that this protein is not essential. This suggests that there may be redundancy or compensatory functions in the mechanisms that stabilise the apical complex.

cell biology↗

bioRxiv2025

Plasmodium ARK1 regulates spindle formation during atypical mitosis and forms a divergent chromosomal passenger complex

Mitosis in Plasmodium spp., the causative agent of malaria, is fundamentally different from model eukaryotes, proceeding via a bipartite microtubule organising centre (MTOC) and lacking canonical regulators such as Polo kinases. During schizogony, asynchronous nuclear replication produces a multinucleate schizont, while rapid male gametogony generates an octaploid nucleus before gamete formation. Here, we identify Aurora-related kinase 1 (ARK1) as a key component of inner MTOC and spindle formation, controlling kinetochore dynamics and driving mitotic progression. Conditional ARK1 depletion disrupts spindle biogenesis, kinetochore segregation, karyokinesis and cytokinesis in both stages, and affects parasite transmission. Interactome analysis shows that ARK1 forms the catalytic core of a non-canonical chromosomal passenger complex (CPC) containing two highly divergent inner centromere proteins (INCENPs), which we term INCENP-A and INCENP-B, and lacking the canonical chromatin-targeting subunits Survivin and Borealin. Comparative genomics suggests that apicomplexan INCENPs arose through recurrent lineage-specific duplications, reflecting an evolutionary rewiring of CPC architecture in this eukaryotic lineage. Together, these findings reveal key adaptations in Plasmodium mitosis involving ARK1 and its INCENP scaffolds, and identify the ARK1-INCENP interface as a potential multistage target for antimalarial intervention.

microbiology↗

bioRxiv2024

Non canonical Sun1-Allan complex orchestrates nuclear envelope remodelling and Basal Body/MTOC Segregation during rapid mitosis in Plasmodium

Mitosis in eukaryotes involves reorganization of the nuclear envelope (NE) and microtubule-organizing centres (MTOCs). During male gametogenesis in Plasmodium, the causative agent of malaria, mitosis is exceptionally rapid and highly divergent. Within 8 min, the haploid male gametocyte genome undergoes three replication cycles (1N to 8N), while maintaining an intact NE. Axonemes assemble in the cytoplasm and connect to a bipartite MTOC-containing nuclear pole (NP) and cytoplasmic basal body, producing eight flagellated gametes. The mechanisms coordinating NE remodelling, MTOC dynamics, and flagellum assembly remain poorly understood. We identify the SUN1-ALLAN complex as a novel mediator of NE remodelling and bipartite MTOC coordination during Plasmodium male gametogenesis. SUN1, a conserved NE protein, localizes to dynamic loops and focal points at the nucleoplasmic face of the spindle poles. ALLAN, a divergent allantoicase, has a location like that of SUN1, and these proteins form a unique complex, detected by live-cell imaging, ultrastructural expansion microscopy, and interactomics. Deletion of either SUN1 or ALLAN genes disrupts nuclear MTOC organization, leading to basal body mis-segregation, defective spindle assembly, and impaired spindle microtubule-kinetochore attachment, but axoneme formation remains intact. Ultrastructural analysis revealed nuclear and cytoplasmic MTOC miscoordination, producing aberrant flagellated gametes lacking nuclear material. These defects block development in the mosquito and parasite transmission, highlighting the essential functions of this complex.

cell biology↗

bioRxiv2024

Divergent Plasmodium protein kinases drive MTOC, kinetochore and axoneme organisation in male gametogenesis

Sexual development and male gamete formation of the malaria parasite in the mosquito midgut is governed by rapid endomitosis in the activated male gametocyte. This process is highly regulated by protein phosphorylation, specifically by three divergent male-specific protein kinases (PKs): CDPK4, SRPK1 and MAP2. Here, we localise each PK during rapid male gamete formation using live-cell imaging, identify their putative substrates by immunoprecipitation, and determine the morphological consequences of their absence using ultrastructure expansion and transmission electron microscopy. Each PK has a distinct location in either the nuclear or cytoplasmic compartment. Protein interaction studies revealed that CDPK4 and MAP2 interact with key drivers of rapid DNA replication, while SRPK1 is involved in RNA translation. The absence of each PK results in severe defects in either microtubule organising centre (MTOC) organisation, kinetochore segregation or axoneme formation. This study reveals the crucial role of these PKs during endomitosis in formation of the flagellated male gamete and uncovers some of their potential substrates that drive this process. Summary blurbThis study reveals how Plasmodium kinases regulate MTOC, axoneme and kinetochore organisation in male gametogenesis, providing key insights into potential targets for malaria transmission control.

microbiology↗

bioRxiv2024

Plasmodium NEK1 coordinates MTOC organisation and kinetochore attachment during rapid mitosis in male gamete formation

Mitosis is an important process in the cell cycle required for cells to divide. Never in mitosis (NIMA)-like kinases (NEKs) are regulators of mitotic functions in diverse organisms. Plasmodium spp, the causative agent of malaria is a divergent unicellular haploid eukaryote with some unusual features in terms of its mitotic and nuclear division cycle that presumably facilitate proliferation in varied environments. For example, during the sexual stage of male gametogenesis that occurs within the mosquito host, an atypical rapid closed endomitosis is observed. Three rounds of genome replication from 1N to 8N and successive cycles of multiple spindle formation and chromosome segregation occur within eight minutes followed by karyokinesis to generate haploid gametes. Our previous Plasmodium berghei kinome screen identified four Nek genes, of which two, NEK2 and NEK4, are required for meiosis. NEK1 is likely to be essential for mitosis in asexual blood stage schizogony in the vertebrate host, but its function during male gametogenesis is unknown. Here, we study NEK1 location and function, using live cell imaging, ultrastructure expansion microscopy (U-ExM) and electron microscopy, together with conditional gene knockdown and proteomic approaches. We report spatiotemporal NEK1 location in real-time, coordinated with microtubule organising centre (MTOC) dynamics during the unusual mitoses at various stages of the Plasmodium spp. life cycle. Knockdown studies reveal NEK1 to be an essential component of the MTOC in male cell differentiation, associated with rapid mitosis, spindle formation and kinetochore attachment. These data suggest that Plasmodium berghei NEK1 kinase is an important component of MTOC organisation and essential regulator of chromosome segregation during male gamete formation.

cell biology↗

bioRxiv2023

PfAP2-MRP DNA-binding protein is a master regulator of parasite pathogenesis during malaria parasite blood stages

Malaria pathogenicity results from the parasites ability to invade, multiply within and then egress from the host red blood cell (RBC). Infected RBCs are remodeled, expressing antigenic variant proteins (such as PfEMP1, coded by the var gene family) for immune evasion and survival. These processes require the concerted actions of many proteins, but the molecular regulation is poorly understood. We have characterized an essential Plasmodium specific Apicomplexan AP2 (ApiAP2) transcription factor in Plasmodium falciparum (PfAP2-MRP; Master Regulator of Pathogenesis) during the intraerythrocytic developmental cycle (IDC). An inducible gene knockout approach showed that PfAP2-MRP is essential for development during the trophozoite stage, and critical for var gene regulation, merozoite development and parasite egress. ChIP-seq experiments performed at 16 hour post invasion (h.p.i.) and 40 h.p.i. matching the two peaks of PfAP2-MRP expression, demonstrate binding of PfAP2-MRP to the promoters of genes controlling trophozoite development and host cell remodeling at 16 h.p.i. and antigenic variation and pathogenicity at 40 h.p.i. Using single-cell RNA-seq and fluorescence-activated cell sorting, we show de-repression of most var genes in{Delta} pfap2-mrp parasites that express multiple PfEMP1 proteins on the surface of infected RBCs. In addition, the{Delta} pfap2-mrp parasites overexpress several early gametocyte marker genes at both 16 and 40 h.p.i., indicating a regulatory role in the sexual stage conversion. Using the Chromosomes Conformation Capture experiment (Hi-C), we demonstrate that deletion of PfAP2-MRP results in significant reduction of both intra-chromosomal and inter-chromosomal interactions in heterochromatin clusters. We conclude that PfAP2-MRP is a vital upstream transcriptional regulator controlling essential processes in two distinct developmental stages during the IDC that include parasite growth, chromatin structure and var gene expression.

genomics↗

bioRxiv2023

Plasmodium ARK2-EB1 axis drives the unconventional spindle dynamics, scaffold formation, and chromosome segregation of sexual transmission stages

Mechanisms of cell division are remarkably diverse, suggesting the underlying molecular networks among eukaryotes differ extensively. The Aurora family of kinases orchestrates the process of chromosome segregation and cytokinesis during cell division through precise spatiotemporal regulation of their catalytic activities by distinct scaffolds. Plasmodium spp., the causative agents of malaria, are unicellular eukaryotes that have three divergent aurora-related kinases (ARKs) and lack most canonical scaffolds/activators. The parasite uses unconventional modes of chromosome segregation during endomitosis and meiosis in sexual transmission stages within mosquito host. This includes a rapid threefold genome replication from 1N to 8N with successive cycles of closed mitosis, spindle formation and chromosome segregation within eight minutes (termed male gametogony). Kinome studies had previously suggested likely essential functions for all three Plasmodium ARKs during asexual mitotic cycles; however, little is known about their location, function, or their scaffolding molecules during unconventional sexual proliferative stages. Using a combination of super-resolution microscopy, mass spectrometry, and live-cell fluorescence imaging, we set out to investigate the role of the atypical Aurora paralog ARK2 to proliferative sexual stages using rodent malaria model Plasmodium berghei. We find that ARK2 primarily localises to the spindle apparatus in the vicinity of kinetochores during both mitosis and meiosis. Interactomics and co-localisation studies reveal a unique ARK2 scaffold at the spindle including the microtubule plus end-binding protein EB1, lacking conserved Aurora scaffold proteins. Gene function studies indicate complementary functions of ARK2 and EB1 in driving endomitotic divisions and thereby parasite transmission. Our discovery of a novel Aurora kinase spindle scaffold underlines the emerging flexibility of molecular networks to rewire and drive unconventional mechanisms of chromosome segregation in the malaria parasite Plasmodium.

cell biology↗

bioRxiv2021

Plasmodium SAS4/CPAP is a flagellum basal body component during male gametogenesis but is not essential for parasite transmission

The centriole/basal body (CBB) is an evolutionarily conserved organelle acting as a microtubule organising centre (MTOC) to nucleate cilia, flagella and the centrosome. SAS4/CPAP is a conserved component associated with BB biogenesis in many model flagellated cells. Plasmodium, a divergent unicellular eukaryote and causative agent of malaria, displays an atypical closed mitosis with an MTOC, reminiscent of the acentriolar MTOC, embedded in the nuclear membrane at most proliferative stages. Mitosis during male gamete formation is accompanied by flagellum formation: within 15 minutes, genome replication (from 1N to 8N) and three successive rounds of mitosis without nuclear division occur, with coordinated axoneme biogenesis in the cytoplasm resulting in eight flagellated gametes. There are two MTOCs in male gametocytes. An acentriolar MTOC located with the nuclear envelope and a centriolar MTOC (basal body) located within the cytoplasm that are required for flagellum assembly. To study the location and function of SAS4 during this rapid process, we examined the spatial profile of SAS4 in real time by live cell imaging and its function by gene deletion. We show its absence during asexual proliferation but its presence and coordinated association and assembly of SAS4 with another basal body component, kinesin8B, which is involved in axoneme biogenesis. In contrast its separation from the nuclear kinetochore marker NDC80 suggests that SAS4 is part of the basal body and outer centriolar MTOC residing in the cytoplasm. However, deletion of the SAS4 gene produced no phenotype, indicating that it is not essential for male gamete formation or parasite transmission through the mosquito.

cell biology↗

bioRxiv2021

Location and function of all Plasmodium kinesins: key roles in parasite proliferation, polarity, and transmission

Kinesins are microtubule-based motors important in cell division, motility, polarity, and intracellular transport in many eukaryotes. However, they are poorly studied in the divergent eukaryotic pathogens- Plasmodium spp., the causative agents of malaria, which manifest atypical aspects of cell division and plasticity of morphology throughout the lifecycle in both mammalian and mosquito hosts. Here we describe a genome-wide screen of Plasmodium kinesins, revealing diverse subcellular locations and functions in spindle assembly, axoneme formation and cell morphology. Surprisingly, only kinesin-13 is essential for growth in the mammalian host while the other eight kinesins are required during the proliferative and invasive stages of parasite transmission through the mosquito vector. In-depth analyses of kinesin-13 and kinesin-20 revealed functions in microtubule dynamics during apical cell polarity formation, spindle assembly, and axoneme biogenesis. These findings help us to understand the importance of microtubule motors and may be exploited to discover new therapeutic interventions against malaria.

cell biology↗

bioRxiv2021

Protein Phosphatase 1 regulates atypical chromosome segregation and cell polarity during mitotic and meiotic division in Plasmodium sexual stages

PP1 is a conserved eukaryotic serine/threonine phosphatase that regulates many aspects of mitosis and meiosis, often working in concert with other phosphatases, such as CDC14 and CDC25. The proliferative stages of the malaria parasite life cycle include sexual development within the mosquito vector, with male gamete formation characterized by an atypical rapid mitosis, consisting of three rounds of DNA synthesis, successive spindle formation with clustered kinetochores, and a meiotic stage during zygote to ookinete development following fertilization. It is unclear how PP1 is involved in these unusual processes. Using real-time live-cell and ultrastructural imaging, conditional gene knockdown, RNA-seq and proteomic approaches, we show that Plasmodium PP1 is implicated in both mitotic exit and, potentially, establishing cell polarity during zygote development in the mosquito midgut, suggesting that small molecule inhibitors of PP1 should be explored for blocking parasite transmission.

cell biology↗

bioRxiv2020

Inhibition of protein N-myristoylation blocks Plasmodium falciparum intraerythrocytic development, egress, and invasion

We have combined chemical biology and genetic modification approaches to investigate the importance of protein myristoylation in the human malaria parasite, Plasmodium falciparum. Parasite treatment during schizogony in the last ten to fifteen hours of the erythrocytic cycle with IMP-1002, an inhibitor of N-myristoyl transferase (NMT), led to a significant blockade in parasite egress from the infected erythrocyte. Two rhoptry proteins were mislocalized in the cell, suggesting that rhoptry function is disrupted. We identified sixteen NMT substrates for which myristoylation was significantly reduced by NMT inhibitor treatment, and of these, six proteins were substantially reduced in abundance. In a viability screen, we showed that for four of these proteins replacement of the N-terminal glycine with alanine to prevent myristoylation had a substantial effect on parasite fitness. In detailed studies of one NMT substrate, glideosome associated protein 45 (GAP45), loss of myristoylation had no impact on protein location or glideosome assembly, in contrast to the disruption caused by GAP45 gene deletion, but GAP45 myristoylation was essential for erythrocyte invasion. Therefore, there are at least three mechanisms by which inhibition of NMT can disrupt parasite development and growth: early in parasite development, leading to the inhibition of schizogony and formation of pseudoschizonts, which has been described previously; at the end of schizogony, with disruption of rhoptry formation, merozoite development and egress from the infected erythrocyte; and at invasion, when impairment of motor complex function prevents invasion of new erythrocytes. These results underline the importance of P. falciparum NMT as a drug target because of the pleiotropic effect of its inhibition.

microbiology↗

bioRxiv2020

MRE11 is crucial for malaria transmission and its absence affects expression of interconnected networks of key genes essential for life

The Meiotic Recombination 11 protein (MRE11) plays a key role in DNA damage response and maintenance of genome stability. However, little is known about its function during development of the malaria parasite Plasmodium. Here, we present a functional, ultrastructural and transcriptomic analysis of Plasmodium MRE11 during its life-cycle in both mammalian and mosquito vector hosts. Genetic disruption of Plasmodium berghei mre11 (PbMRE11) results in significant retardation of oocyst development in the mosquito midgut associated with cytoplasmic and nuclear degeneration, along with concomitant ablation of sporogony and subsequent parasite transmission. Further, absence of PbMRE11 results in significant transcriptional downregulation of genes involved in key interconnected biological processes that are fundamental to all eukaryotic life including ribonucleoprotein biogenesis, spliceosome function and iron-sulphur cluster assembly. Overall, our study provides a comprehensive functional analysis of MRE11s role in Plasmodium development during the mosquito stages and offers a potential target for therapeutic intervention during malaria parasite transmission.

cell biology↗

bioRxiv2020

Plasmodium berghei kinesin-5 associates with the spindle apparatus during cell division but is dispensable for parasite proliferation

Kinesin-5 motors play essential roles in spindle apparatus assembly during cell division, by generating forces to establish and maintain the spindle bipolarity essential for proper chromosome segregation. Kinesin-5 is largely conserved structurally and functionally in model eukaryotes, but its role is unknown in the Plasmodium parasite, an evolutionarily divergent organism with several atypical features of both mitotic and meiotic cell division. We have investigated the function and subcellular location of kinesin-5 during cell division throughout the Plasmodium berghei life cycle. Deletion of kinesin-5 had little visible effect at any proliferative stage except sporozoite production in oocysts, resulting in a significant decrease in the number of motile sporozoites in mosquito salivary glands, which were able to infect a new vertebrate host. Live-cell imaging showed kinesin-5-GFP located on the spindle and at spindle poles during both atypical mitosis and meiosis. Fixed-cell immunofluorescence assays revealed kinesin-5 co-localized with -tubulin and centrin-2 and a partial overlap with kinetochore marker NDC80 during early blood stage schizogony. Dual-colour live-cell imaging showed that kinesin-5 is closely associated with NDC80 during male gametogony, but not with kinesin-8B, a marker of the basal body and axonemes of the forming flagella. Treatment of gametocytes with microtubule-specific inhibitors confirmed kinesin-5 association with nuclear spindles and not cytoplasmic axonemal microtubules. Altogether, our results demonstrate that kinesin-5 is associated with the spindle apparatus, expressed in proliferating parasite stages, and important for efficient production of infectious sporozoites.

cell biology↗

bioRxiv2020

A 3-hydroxyacyl-CoA dehydratase (DEH) involved in very long chain fatty acid synthesis is crucial for oocyst mitotic division but not cell size during parasite transmission in Plasmodium

Cells use fatty acids (FAs) for membrane biosynthesis, energy storage and the generation of signaling molecules. 3-hydroxyacyl-CoA dehydratase - DEH - is a key component of very long chain FA (VLCFA) synthesis. Here, we further characterized in-depth the location and function of DEH, applying in silico analysis, live cell imaging, reverse genetics and ultrastructure analysis using the mouse malaria model Plasmodium berghei. DEH is evolutionarily conserved across eukaryotes, with a single DEH in Plasmodium spp. and up to three orthologs in the other eukaryotes studied. DEH-GFP live-cell imaging showed strong GFP fluorescence throughout the life-cycle, with areas of localized expression in the cytoplasm and a circular ring pattern around the nucleus that colocalized with ER markers. {Delta}deh mutants showed a small but significant reduction in oocyst size compared to WT controls from day 10 post-infection onwards and endomitotic cell division and sporogony were completely ablated, blocking parasite transmission from mosquito to vertebrate host. Ultrastructure analysis confirmed degeneration of {Delta}deh oocysts, and a complete lack of sporozoite budding. Overall, DEH is evolutionarily conserved, localizes to the ER and plays a crucial role in sporogony.

cell biology↗

bioRxiv2020

A divergent cyclin/cyclin-dependent kinase complex controls the atypical replication of Plasmodium berghei during gametogony and parasite transmission.

Cell cycle transitions are generally triggered by variation in the activity of cyclin-dependent kinases (CDKs) bound to cyclins. Malaria-causing parasites have a life cycle with unique cell-division cycles, and a repertoire of divergent CDKs and cyclins of poorly understood function and interdependency. We show that Plasmodium berghei CDK-related kinase 5 (CRK5), is a critical regulator of atypical mitosis in the gametogony and is required for mosquito transmission. It phosphorylates canonical CDK motifs of components in the pre-replicative complex and is essential for DNA replication. During a replicative cycle, CRK5 stably interacts with a single Plasmodium-specific cyclin (SOC2), although we obtained no evidence of SOC2 cycling by transcription, translation or degradation. Our results provide evidence that during Plasmodium male gametogony, this divergent cyclin/CDK pair fills the functional space of other eukaryotic cell-cycle kinases controlling DNA replication.

microbiology↗