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Organizational changes of the daughter basal complex during the parasite replication of Toxoplasma gondii.

Hu K - PLoS Pathog. (2008)

Bottom Line: This study focuses on key events during the biogenesis of the basal complex using high resolution light microscopy, and reveals that daughter basal complexes are established around the duplicated centrioles independently of the structural integrity of the daughter cortical cytoskeleton, and that they are dynamic "caps" at the growing ends of the daughters.This correlates with the constriction of the basal complex, a process that can be artificially induced by increasing cellular calcium concentration.The basal complex is therefore likely to be a new kind of centrin-based contractile apparatus.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Indiana University, Bloomington, Indiana, United States of America. kehu@indiana.edu

ABSTRACT
The apicomplexans are a large group of parasitic protozoa, many of which are important human and animal pathogens, including Plasmodium falciparum and Toxoplasma gondii. These parasites cause disease only when they replicate, and their replication is critically dependent on the proper assembly of the parasite cytoskeletons during cell division. In addition to their importance in pathogenesis, the apicomplexan parasite cytoskeletons are spectacular structures. Therefore, understanding the cytoskeletal biogenesis of these parasites is important not only for parasitology but also of general interest to broader cell biology. Previously, we found that the basal end of T. gondii contains a novel cytoskeletal assembly, the basal complex, a cytoskeletal compartment constructed in concert with the daughter cortical cytoskeleton during cell division. This study focuses on key events during the biogenesis of the basal complex using high resolution light microscopy, and reveals that daughter basal complexes are established around the duplicated centrioles independently of the structural integrity of the daughter cortical cytoskeleton, and that they are dynamic "caps" at the growing ends of the daughters. Compartmentation and polarization of the basal complex is first revealed at a late stage of cell division upon the recruitment of an EF-hand containing calcium binding protein, TgCentrin2. This correlates with the constriction of the basal complex, a process that can be artificially induced by increasing cellular calcium concentration. The basal complex is therefore likely to be a new kind of centrin-based contractile apparatus.

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Related in: MedlinePlus

The Establishment, Construction, and Maturation of the Basal Complex throughout the Cell CycleA collection of the enlarged insets from (left) Figure 3B; Figure S3; Figure 8A–8C and Figure 1D (right) for side-by-side comparison of morphological and molecular composition differences among basal complexes at different stages of construction and maturation. For ease of comparison, all images are oriented such that the posterior end of the parasite is closer to the bottom. Scale bar = 0.5 μm
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ppat-0040010-g009: The Establishment, Construction, and Maturation of the Basal Complex throughout the Cell CycleA collection of the enlarged insets from (left) Figure 3B; Figure S3; Figure 8A–8C and Figure 1D (right) for side-by-side comparison of morphological and molecular composition differences among basal complexes at different stages of construction and maturation. For ease of comparison, all images are oriented such that the posterior end of the parasite is closer to the bottom. Scale bar = 0.5 μm

Mentions: Interestingly, although TgCentrin2 is hardly detectable in the basal ring complex earlier during cell division (cf. Figure 3B and Figure S3), it is clearly localized to the daughter basal complex as a ring at a late stage when the daughter basal complex appears to be constricted (Figure 8A). Its ring-like localization in the basal complex is also pronounced during cytokinesis when the daughters start to take over mother's plasma membrane (Figure 8B), and after cytokinesis when the basal complex is still open at both ends (Figure 8C). In all cases, the TgCentrin2 basal ring is located to the posterior of the TgMORN1 ring (Figures 8 and 9). The compartmentation and polarization of the basal complex are thus revealed upon the recruitment of TgCentrin2 prior to the closure of the basal complex.


Organizational changes of the daughter basal complex during the parasite replication of Toxoplasma gondii.

Hu K - PLoS Pathog. (2008)

The Establishment, Construction, and Maturation of the Basal Complex throughout the Cell CycleA collection of the enlarged insets from (left) Figure 3B; Figure S3; Figure 8A–8C and Figure 1D (right) for side-by-side comparison of morphological and molecular composition differences among basal complexes at different stages of construction and maturation. For ease of comparison, all images are oriented such that the posterior end of the parasite is closer to the bottom. Scale bar = 0.5 μm
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2211554&req=5

ppat-0040010-g009: The Establishment, Construction, and Maturation of the Basal Complex throughout the Cell CycleA collection of the enlarged insets from (left) Figure 3B; Figure S3; Figure 8A–8C and Figure 1D (right) for side-by-side comparison of morphological and molecular composition differences among basal complexes at different stages of construction and maturation. For ease of comparison, all images are oriented such that the posterior end of the parasite is closer to the bottom. Scale bar = 0.5 μm
Mentions: Interestingly, although TgCentrin2 is hardly detectable in the basal ring complex earlier during cell division (cf. Figure 3B and Figure S3), it is clearly localized to the daughter basal complex as a ring at a late stage when the daughter basal complex appears to be constricted (Figure 8A). Its ring-like localization in the basal complex is also pronounced during cytokinesis when the daughters start to take over mother's plasma membrane (Figure 8B), and after cytokinesis when the basal complex is still open at both ends (Figure 8C). In all cases, the TgCentrin2 basal ring is located to the posterior of the TgMORN1 ring (Figures 8 and 9). The compartmentation and polarization of the basal complex are thus revealed upon the recruitment of TgCentrin2 prior to the closure of the basal complex.

Bottom Line: This study focuses on key events during the biogenesis of the basal complex using high resolution light microscopy, and reveals that daughter basal complexes are established around the duplicated centrioles independently of the structural integrity of the daughter cortical cytoskeleton, and that they are dynamic "caps" at the growing ends of the daughters.This correlates with the constriction of the basal complex, a process that can be artificially induced by increasing cellular calcium concentration.The basal complex is therefore likely to be a new kind of centrin-based contractile apparatus.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Indiana University, Bloomington, Indiana, United States of America. kehu@indiana.edu

ABSTRACT
The apicomplexans are a large group of parasitic protozoa, many of which are important human and animal pathogens, including Plasmodium falciparum and Toxoplasma gondii. These parasites cause disease only when they replicate, and their replication is critically dependent on the proper assembly of the parasite cytoskeletons during cell division. In addition to their importance in pathogenesis, the apicomplexan parasite cytoskeletons are spectacular structures. Therefore, understanding the cytoskeletal biogenesis of these parasites is important not only for parasitology but also of general interest to broader cell biology. Previously, we found that the basal end of T. gondii contains a novel cytoskeletal assembly, the basal complex, a cytoskeletal compartment constructed in concert with the daughter cortical cytoskeleton during cell division. This study focuses on key events during the biogenesis of the basal complex using high resolution light microscopy, and reveals that daughter basal complexes are established around the duplicated centrioles independently of the structural integrity of the daughter cortical cytoskeleton, and that they are dynamic "caps" at the growing ends of the daughters. Compartmentation and polarization of the basal complex is first revealed at a late stage of cell division upon the recruitment of an EF-hand containing calcium binding protein, TgCentrin2. This correlates with the constriction of the basal complex, a process that can be artificially induced by increasing cellular calcium concentration. The basal complex is therefore likely to be a new kind of centrin-based contractile apparatus.

Show MeSH
Related in: MedlinePlus