Editorial: Celebrating Microbial Diversity: The Many Cell Cycles of Eukaryotic Microbes.

Editorial on the Research Topic Celebrating Microbial Diversity: The Many Cell Cycles of Eukaryotic MicrobesCM: ERC research grant ‘Plasmocycle’. ZL: NIH R01 grant AI101437. MB: Swiss National Science Foundation 31003A_179321

Habiter le dedans et le dehors : la maison ou l’Eden rêvé et recréé

Avec pour hypothèse commune que la montée actuelle de la « question habitante » dans les sociétés post industrielles oblige à mettre au centre de l’investigation : . le point de vue de l’individu habitant, à partir duquel il faut tenter de définir les « cultures de la nature », les représentations de la valeur des lieux, les catégories par lesquelles chaque sujet pense sa « géographicité » ; 2. les catégories de rural et d’urbain rendent possible la mise en évidence des propriétés et des qualités de chaque milieu quel que soit le pays d'Europe concerné. Les auteurs tentent de dégager des résultats transversaux des récits de lieux de vie obtenus dans leurs terrains spécifiques de recherche. Ils aboutissent à une problématique collective et à une méthodologie à mettre en place pour approfondir ce qu’habiter veut dire aujourd’hui dans les représentations et les pratiques des ruraux et des urbains. La contradiction entre le chez soi pensé et pratiqué comme « espace refuge » ou « dedans » et le chez soi vu comme appropriation de l’abord et intégration de la discontinuité du dehors est un principe de distinction fort pour aller vers une typologie des « modes d’habiter ».The authors base their reflection on the common assumption that the growing importance of the “living issue” in post-industrial societies compels them to focus their investigation on: 1) the point of view of the resident, from which they must try to define the “cultures of nature”, the representations of the value of the place and the categories through which each individual relates to his “geographicity”; 2) the categories of the rural and the urban whose confrontation is likely to evidence the qualities and properties of any European-based “milieu”. The authors then synthetise the data provided by the narratives collected in their own fields of investigation. They can thus formulate a common question and methodology in order to reflect on what “living” means today in the representations and practices of country people and city dwellers. The contradiction between the home considered and experienced as a shelter or “inside” and the home seen as an appropriation of the margins and integration of the discontinuity of the “outside” is a strong distinctive principle to head towards a typology of the “ways of living”

Habiter le dedans et le dehors : la maison ou l’Eden rêvé et recréé

Avec pour hypothèse commune que la montée actuelle de la « question habitante » dans les sociétés post industrielles oblige à mettre au centre de l’investigation : . le point de vue de l’individu habitant, à partir duquel il faut tenter de définir les « cultures de la nature », les représentations de la valeur des lieux, les catégories par lesquelles chaque sujet pense sa « géographicité » ; 2. les catégories de rural et d’urbain rendent possible la mise en évidence des propriétés et des qualités de chaque milieu quel que soit le pays d'Europe concerné. Les auteurs tentent de dégager des résultats transversaux des récits de lieux de vie obtenus dans leurs terrains spécifiques de recherche. Ils aboutissent à une problématique collective et à une méthodologie à mettre en place pour approfondir ce qu’habiter veut dire aujourd’hui dans les représentations et les pratiques des ruraux et des urbains. La contradiction entre le chez soi pensé et pratiqué comme « espace refuge » ou « dedans » et le chez soi vu comme appropriation de l’abord et intégration de la discontinuité du dehors est un principe de distinction fort pour aller vers une typologie des « modes d’habiter ».The authors base their reflection on the common assumption that the growing importance of the “living issue” in post-industrial societies compels them to focus their investigation on: 1) the point of view of the resident, from which they must try to define the “cultures of nature”, the representations of the value of the place and the categories through which each individual relates to his “geographicity”; 2) the categories of the rural and the urban whose confrontation is likely to evidence the qualities and properties of any European-based “milieu”. The authors then synthetise the data provided by the narratives collected in their own fields of investigation. They can thus formulate a common question and methodology in order to reflect on what “living” means today in the representations and practices of country people and city dwellers. The contradiction between the home considered and experienced as a shelter or “inside” and the home seen as an appropriation of the margins and integration of the discontinuity of the “outside” is a strong distinctive principle to head towards a typology of the “ways of living”

Plasmodium ARK2 and EB1 drive unconventional spindle dynamics, during chromosome segregation in sexual transmission stages

The Aurora family of kinases orchestrates chromosome segregation and cytokinesis during cell division, with precise spatiotemporal regulation of its catalytic activities by distinct protein scaffolds. Plasmodium spp., the causative agents of malaria, are unicellular eukaryotes with three unique and highly divergent aurora-related kinases (ARK1-3) that are essential for asexual cellular proliferation but lack most canonical scaffolds/activators. Here we investigate the role of ARK2 during sexual proliferation of the rodent malaria Plasmodium berghei, using a combination of super-resolution microscopy, mass spectrometry, and live-cell fluorescence imaging. We find that ARK2 is primarily located at spindle microtubules in the vicinity of kinetochores during both mitosis and meiosis. Interactomic and co-localisation studies reveal several putative ARK2-associated interactors including the microtubule-interacting protein EB1, together with MISFIT and Myosin-K, but no conserved eukaryotic scaffold proteins. Gene function studies indicate that ARK2 and EB1 are complementary in driving endomitotic division and thereby parasite transmission through the mosquito. This discovery underlines the flexibility of molecular networks to rewire and drive unconventional mechanisms of chromosome segregation in the malaria parasite.</p

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 8 min followed by karyokinesis to generate haploid gametes. Our previous Plasmodium berghei kinome screen identified 4 Nek genes, of which 2, 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 P. berghei NEK1 kinase is an important component of MTOC organisation and essential regulator of chromosome segregation during male gamete formation

Protein phosphatase 1 regulates atypical 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 livecell 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

Genome-wide functional analysis reveals key roles for kinesins in the mammalian and mosquito stages of the malaria parasite life cycle

Kinesins are microtubule (MT)-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 life cycle 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 8 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 MT dynamics during apical cell polarity formation, spindle assembly, and axoneme biogenesis. These findings help us to understand the importance of MT motors and may be exploited to discover new therapeutic interventions against malaria

A divergent cyclin/cyclin-dependent kinase complex controls the atypical replication of a malaria parasite during gametogony and 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

Ca2+ signals critical for egress and gametogenesis in malaria parasites depend on a multipass membrane protein that interacts with PKG.

Calcium signaling regulated by the cGMP-dependent protein kinase (PKG) controls key life cycle transitions in the malaria parasite. However, how calcium is mobilized from intracellular stores in the absence of canonical calcium channels in Plasmodium is unknown. Here, we identify a multipass membrane protein, ICM1, with homology to transporters and calcium channels that is tightly associated with PKG in both asexual blood stages and transmission stages. Phosphoproteomic analyses reveal multiple ICM1 phosphorylation events dependent on PKG activity. Stage-specific depletion of Plasmodium berghei ICM1 prevents gametogenesis due to a block in intracellular calcium mobilization, while conditional loss of Plasmodium falciparum ICM1 is detrimental for the parasite resulting in severely reduced calcium mobilization, defective egress, and lack of invasion. Our findings suggest that ICM1 is a key missing link in transducing PKG-dependent signals and provide previously unknown insights into atypical calcium homeostasis in malaria parasites essential for pathology and disease transmission