The Basal Complex Protein PfMORN1 Is Not Required for Asexual Replication of Plasmodium falciparum

Plasmodium falciparum parasites cause the most severe form of human malaria. During the clinically relevant blood stage of its life cycle, the parasites divide via schizogony.

A more complex basal complex: novel components mapped to the Toxoplasma gondii cytokinesis machinery portray an expanded hierarchy of its assembly and function

The basal complex (BC) of Toxoplasma gondii has an essential role in cell division but details on the mechanism are lacking. To promote insights in this process, reciprocal proximity based biotinylation was used to map the basal complex proteome. An assembled protein map was interrogated by spatiotemporal characterization of critical components as well as functionally by disrupting the expression of the components. Spatially, this revealed four proteins sub-complexes with distinct sub-structural BC localization. Temporally, several patterns were differentiated based on their first appearance and/or disappearance from the BC corresponding with different steps in BC development (initiation, expansion, constriction, maturation). We also identified a protein pre-ceding BC formation (BCC0) laid out in a 5-fold symmetry. This symmetry marks the apical annuli and site of alveolar suture formation. From here, it was determined that the apical cap is assembled in the apical direction, whereas the rest of the IMC expands in the basal direction, inspiring a new bi-directional daughter budding process. Furthermore, we discovered BCC4, an essential protein exclusively localizing to the BC during cell division. Although depletion of BCC4 did not prevent BC formation, it led to BC fragmentation at the mid-point of cell division. Based on these data, a model is presented wherein BCC4 and MORN1 stabilize each other and form a rubber band that implies an essential role for the BC in preventing the fraying of the basal end of the assembling daughter cytoskeleton scaffolds. Furthermore, one new component of the Myosin J and Centrin2 cluster was BCC1, a hypothetical protein whose depletion prevents the non-essential last step of BC constriction. Overall, the BC is a highly dynamic, multi-functional structure that is critical to the hierarchical assembly of the daughter parasites.

A dynamic basal complex modulates mammalian sperm movement

Reproductive success depends on efficient sperm movement driven by axonemal dynein-mediated microtubule sliding. Models predict sliding at the base of the tail – the centriole – but such sliding has never been observed. Centrioles are ancient organelles with a conserved architecture; their rigidity is thought to restrict microtubule sliding. Here, we show that, in mammalian sperm, the atypical distal centriole (DC) and its surrounding atypical pericentriolar matrix form a dynamic basal complex (DBC) that facilitates a cascade of internal sliding deformations, coupling tail beating with asymmetric head kinking. During asymmetric tail beating, the DC’s right side and its surroundings slide ~300 nm rostrally relative to the left side. The deformation throughout the DBC is transmitted to the head-tail junction; thus, the head tilts to the left, generating a kinking motion. These findings suggest that the DBC evolved as a dynamic linker coupling sperm head and tail into a single self-coordinated system.

The Ringleaders: Understanding the Apicomplexan Basal Complex Through Comparison to Established Contractile Ring Systems

The actomyosin contractile ring is a key feature of eukaryotic cytokinesis, conserved across many eukaryotic kingdoms. Recent research into the cell biology of the divergent eukaryotic clade Apicomplexa has revealed a contractile ring structure required for asexual division in the medically relevant genera Toxoplasma and Plasmodium; however, the structure of the contractile ring, known as the basal complex in these parasites, remains poorly characterized and in the absence of a myosin II homolog, it is unclear how the force required of a cytokinetic contractile ring is generated. Here, we review the literature on the basal complex in Apicomplexans, summarizing what is known about its formation and function, and attempt to provide possible answers to this question and suggest new avenues of study by comparing the Apicomplexan basal complex to well-studied, established cytokinetic contractile rings and their mechanisms in organisms such as S. cerevisiae and D. melanogaster. We also compare the basal complex to structures formed during mitochondrial and plastid division and cytokinetic mechanisms of organisms beyond the Opisthokonts, considering Apicomplexan diversity and divergence.

A dynamic basal complex modulates mammalian sperm movement

Reproductive success depends on efficient sperm movement driven by dynein-mediated microtubule sliding in the axoneme 1-3. Models predict sliding at the base of the tail – the centriole – but such sliding has never been observed 4,5. Centrioles are evolutionarily-ancient organelles with a conserved architecture 6-8, and their rigidity is thought to restrict microtubule sliding 1. Here, we show that, in mammalian sperm, the atypical distal centriole (DC) and its surrounding atypical pericentriolar matrix 9,10 form a dynamic basal complex (DBC) that facilitates a cascade of internal sliding deformations, coupling tail beating with asymmetric head kinking. During asymmetric tail beating, the DC’s right side and its surroundings slide ~300 nm rostrally relative to the left side. This deformation is transmitted through the DBC to the head-tail junction; as a result, the head tilts to the left, generating a kinking motion. These findings suggest that the DBC evolved to act as a mechanotransducer, coupling sperm head and tail into a single self-coordinated system. The DBC may act as a morphological computer 11, regulating tail beating from external feedback imparted to the head during sperm navigation. We anticipate our findings will enable studies of coordinated motion in sperm and cilia in many contexts.

A dynamic basal complex modulates mammalian sperm movement

Reproductive success depends on efficient sperm movement driven by dynein-mediated microtubule sliding in the axoneme 1-3. Models predict sliding at the base of the tail – the centriole – but such sliding has never been observed 4,5. Centrioles are evolutionarily-ancient organelles with a conserved architecture 6-8, and their rigidity is thought to restrict microtubule sliding 1. Here, we show that, in mammalian sperm, the atypical distal centriole (DC) and its surrounding atypical pericentriolar matrix 9,10 form a dynamic basal complex (DBC) that facilitates a cascade of internal sliding deformations, coupling tail beating with asymmetric head kinking. During asymmetric tail beating, the DC’s right side and its surroundings slide ~300 nm rostrally relative to the left side. This deformation is transmitted through the DBC to the head-tail junction; as a result, the head tilts to the left, generating a kinking motion. These findings suggest that the DBC evolved to act as a mechanotransducer, coupling sperm head and tail into a single self-coordinated system. The DBC may act as a morphological computer 11, regulating tail beating from external feedback imparted to the head during sperm navigation. We anticipate our findings will enable studies of coordinated motion in sperm and cilia in many contexts.

A dynamic basal complex modulates mammalian sperm movement

Reproductive success depends on efficient sperm movement driven by dynein-mediated microtubule sliding in the axoneme 1-3. Models predict sliding at the base of the tail – the centriole – but such sliding has never been observed 4,5. Centrioles are evolutionarily-ancient organelles with a conserved architecture 6-8, and their rigidity is thought to restrict microtubule sliding 1. Here, we show that, in mammalian sperm, the atypical distal centriole (DC) and its surrounding atypical pericentriolar matrix 9,10 form a dynamic basal complex (DBC) that facilitates a cascade of internal sliding deformations, coupling tail beating with asymmetric head kinking. During asymmetric tail beating, the DC’s right side and its surroundings slide ~300 nm rostrally relative to the left side. This deformation is transmitted through the DBC to the head-tail junction; as a result, the head tilts to the left, generating a kinking motion. These findings suggest that the DBC evolved to act as a mechanotransducer, coupling sperm head and tail into a single self-coordinated system. The DBC may act as a morphological computer 11, regulating tail beating from external feedback imparted to the head during sperm navigation. We anticipate our findings will enable studies of coordinated motion in sperm and cilia in many contexts.

Arquitectura estratigráfica, paleogeografía y proveniencia sedimentaria de las rocas cenozoicas del sur de Perú (Tacna, 18° S)

The Cenozoic rocks lying in the Province of Tacna (18° S), southern Perú, represent approximately 600 m of stratigraphic thickness. This stacking groups the Sotillo (Paleocene), Moquegua Inferior (Eocene), Moquegua Superior (Oligocene), Huaylillas (Miocene) and Millo formations (Pliocene), and these are the sedimentary fill of the Moquegua Basin. The sediments of the three latter formations are organized into nine sedimentary facies and five architectural elements. Their facies associations suggest the existence of an ancient highly channelized multi-lateral fluvial braided system, with upward increase of pyroclastic and conglomeratic depositions. The heavy mineral spectra make each lithostratigraphic unit unique and distinguishable, being the sediments of the Moquegua Superior Formation rich in garnets, titanites and zircons; while the sediments of the Huaylillas and Millo formations in clinopyroxenes. This mineral arrangement becomes an excellent tool for stratigraphic correlations between outcrops and subsurface stratigraphy (by means of well cores studies) and allow to sketch out a new stratigraphic framework and a complex of rocky blocks bounded by normal faults, often tilted. The sediment mineralogy also suggests that the rocks conforming the Western Cordillera were the main source of sediments for the Moquegua Basin in Tacna. In this context, the detritus of the Moquegua Superior Formation derives mainly from the erosion of the rocks forming the Coastal Basal Complex (Proterozoic), the Ambo Group (Carboniferous) and the Junerata/Chocolate Formation (Early Jurassic). The Huaylillas Formation is a pyroclastic and sedimentary unit which components derived mainly from the Huaylillas volcanism (Miocene) and partly from the denudation of the Toquepala Group (Late Cretaceous). The Huaylillas Formation widely contrasts to the underlying Moquegua Superior Formation due its mineralogy and facies. Finally, the detritus of the Millo Formation derived mostly from the rocks forming the Barroso Formation (Pliocene), and their facies represent a higher contrast in relation to the underlying units due its notorious conglomerate facies.

Tectono-metamorphic evolution of shallow crustal levels within active volcanic arcs. Insights from the exhumed Basal Complex of Basse-Terre (Guadeloupe, French West Indies)

In order to decipher the tectono-metamorphic evolution of shallow crustal levels of the active volcanic arc of the Guadeloupe archipelago (Lesser Antilles) we present new geochemical, geochronological, mineralogical and structural investigations of the so-called Basal Complex, the oldest and most eroded volcanic complex of Basse-Terre in Guadeloupe. Based on geochemical and mineralogical criteria we propose an updated geological map of this northern area of Basse-Terre. Using 40Ar–39Ar geochronology we demonstrate first that the eroded “Gros Morne” of Deshaies belong to the Basal Complex, and second that this complex is characterized by 4.3 to 2 Ma old volcanism. Structural analysis reveals a long-lived deformation history with the development through time of N80-N100 schistose zones; N110-N140 and N160-N10 oriented hydrothermal breccias and N140-N150 brittle normal faults. The boundary between the Basal Complex and the southernmost Septentrional Chain corresponds to a series of faults with N 150° and N 50° main directions. Detailed mineralogical and petrological investigations, including thermodynamic modeling, allow the identification of three phases of post-magmatic mineralogical transformations with first a high-temperature stage under Greenschist to sub-Greenschist facies conditions (0.6–2 kbar for 250–300 °C), a re-equilibration under Zeolite facies conditions and finally a sub-surface alteration. The consistency between P–T conditions of metamorphism and the present day measured geothermal gradient demonstrates that the metamorphic pattern is the record of hydrothermal fluids circulation during building and cooling of the Lesser Antilles magmatic arc. The tectono-metamorphic evolution recognized in the Basal Complex enables us to propose a conceptual model for heat and fluid transport within shallow crustal levels of the Guadeloupe active volcanic arc.