Limits...
A cell-body groove housing the new flagellum tip suggests an adaptation of cellular morphogenesis for parasitism in the bloodstream form of Trypanosoma brucei.

Hughes L, Towers K, Starborg T, Gull K, Vaughan S - J. Cell. Sci. (2013)

Bottom Line: We suggest that the groove has a similar function to the flagella connector.The groove is a mobile junction located alongside the microtubule quartet (MtQ) and occurred within a gap in the subpellicular microtubule corset, causing significant modification of microtubules during elongation of the new flagellum.It appears likely that this novel form of morphogenetic structure has evolved to withstand the hostile immune response in the mammalian blood.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Medical Sciences, Faculty of Health and Life Science, Oxford Brookes University, Oxford OX3 0BP, UK.

ABSTRACT
Flagella are highly conserved organelles present in a wide variety of species. In Trypanosoma brucei the single flagellum is necessary for morphogenesis, cell motility and pathogenesis, and is attached along the cell body. A new flagellum is formed alongside the old during the cell division cycle. In the (insect) procyclic form, the flagella connector (FC) attaches the tip of the new flagellum to the side of the old flagellum, ensuring faithful replication of cell architecture. The FC is not present in the bloodstream form of the parasite. We show here, using new imaging techniques including serial block-face scanning electron microscopy (SBF-SEM), that the distal tip of the new flagellum in the bloodstream form is embedded within an invagination in the cell body plasma membrane, named the groove. We suggest that the groove has a similar function to the flagella connector. The groove is a mobile junction located alongside the microtubule quartet (MtQ) and occurred within a gap in the subpellicular microtubule corset, causing significant modification of microtubules during elongation of the new flagellum. It appears likely that this novel form of morphogenetic structure has evolved to withstand the hostile immune response in the mammalian blood.

Show MeSH

Related in: MedlinePlus

Morphogenetic characteristics of the groove revealed by SBF-SEM. (A) Surface volume rendering of SBF-SEM data shows the posterior (P) end of a cell containing the old flagellum (OF, purple) and a short new flagellum (NF, red), emerging from the flagellar pocket (green), basal bodies are also indicated (BB). The new flagellum has its distal tip embedded in a groove (arrow) of plasma membrane (yellow). The anterior end (a) of the section of cell shown is indicated. (B) Surface volume of segmented whole cell. The new flagellum is located in a groove within the body of the cell (arrow). Nuclei (N) are indicated. (C) Cell with a long new flagellum that has extended beyond the anterior tip of the cell (arrow) and lacks evidence of a groove. (D) Chart showing the relative positions (means±s.d.) of the new flagellum tip (1–4 in the diagram and along the x-axis of the graph) during flagellum elongation. A statistically significant increase (*, **, *** P<0.001) in the length of flagellar tip completely surrounded by the cell body plasma membrane is observed with respect to flagellum length (n≥4 for each position). Scale bars: ∼500 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3860315&req=5

f05: Morphogenetic characteristics of the groove revealed by SBF-SEM. (A) Surface volume rendering of SBF-SEM data shows the posterior (P) end of a cell containing the old flagellum (OF, purple) and a short new flagellum (NF, red), emerging from the flagellar pocket (green), basal bodies are also indicated (BB). The new flagellum has its distal tip embedded in a groove (arrow) of plasma membrane (yellow). The anterior end (a) of the section of cell shown is indicated. (B) Surface volume of segmented whole cell. The new flagellum is located in a groove within the body of the cell (arrow). Nuclei (N) are indicated. (C) Cell with a long new flagellum that has extended beyond the anterior tip of the cell (arrow) and lacks evidence of a groove. (D) Chart showing the relative positions (means±s.d.) of the new flagellum tip (1–4 in the diagram and along the x-axis of the graph) during flagellum elongation. A statistically significant increase (*, **, *** P<0.001) in the length of flagellar tip completely surrounded by the cell body plasma membrane is observed with respect to flagellum length (n≥4 for each position). Scale bars: ∼500 nm.

Mentions: Morphogenetic characteristics of the groove were investigated using SBF-SEM. The technique provides 3D data from large numbers of whole cells at slightly lower resolution than tomography. Volumes containing adjacent serial sections (100-nm thick) of individual trypanosomes with a new flagellum of different lengths were extracted from SBF-SEM datasets and modeled. The morphology was comparable to that obtained by conventional SEM (compare Fig. 5A–C and Fig. 1A,B) and also revealed the internal ultrastructure of the cells. This technique permitted unequivocal identification of the distal tip of the new flagellum and full three-dimensional analysis of the cells and the groove. Analysis of cells with a very short new flagellum that had just exited the flagellar pocket demonstrated that the groove was first located at the point where the distal tip of the new flagellum exited the flagellar pocket. This is best illustrated by viewing supplementary material Movie 4 of the cell shown in Fig. 5A. A groove was observed in all whole-cell reconstructions where the cell possessed a new flagellum that had exited the flagellar pocket, but had not reached the anterior end of the cell. This is best illustrated by viewing supplementary material Movie 5 of the cell imaged in Fig. 5B. In cells where the new flagellum had extended to the anterior end of the cell but had not extended beyond it, a groove structure was evident. However, in cells where the new flagellum was beyond the anterior tip of the cell (Fig. 5C) or had begun cytokinesis no groove was observed.


A cell-body groove housing the new flagellum tip suggests an adaptation of cellular morphogenesis for parasitism in the bloodstream form of Trypanosoma brucei.

Hughes L, Towers K, Starborg T, Gull K, Vaughan S - J. Cell. Sci. (2013)

Morphogenetic characteristics of the groove revealed by SBF-SEM. (A) Surface volume rendering of SBF-SEM data shows the posterior (P) end of a cell containing the old flagellum (OF, purple) and a short new flagellum (NF, red), emerging from the flagellar pocket (green), basal bodies are also indicated (BB). The new flagellum has its distal tip embedded in a groove (arrow) of plasma membrane (yellow). The anterior end (a) of the section of cell shown is indicated. (B) Surface volume of segmented whole cell. The new flagellum is located in a groove within the body of the cell (arrow). Nuclei (N) are indicated. (C) Cell with a long new flagellum that has extended beyond the anterior tip of the cell (arrow) and lacks evidence of a groove. (D) Chart showing the relative positions (means±s.d.) of the new flagellum tip (1–4 in the diagram and along the x-axis of the graph) during flagellum elongation. A statistically significant increase (*, **, *** P<0.001) in the length of flagellar tip completely surrounded by the cell body plasma membrane is observed with respect to flagellum length (n≥4 for each position). Scale bars: ∼500 nm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3860315&req=5

f05: Morphogenetic characteristics of the groove revealed by SBF-SEM. (A) Surface volume rendering of SBF-SEM data shows the posterior (P) end of a cell containing the old flagellum (OF, purple) and a short new flagellum (NF, red), emerging from the flagellar pocket (green), basal bodies are also indicated (BB). The new flagellum has its distal tip embedded in a groove (arrow) of plasma membrane (yellow). The anterior end (a) of the section of cell shown is indicated. (B) Surface volume of segmented whole cell. The new flagellum is located in a groove within the body of the cell (arrow). Nuclei (N) are indicated. (C) Cell with a long new flagellum that has extended beyond the anterior tip of the cell (arrow) and lacks evidence of a groove. (D) Chart showing the relative positions (means±s.d.) of the new flagellum tip (1–4 in the diagram and along the x-axis of the graph) during flagellum elongation. A statistically significant increase (*, **, *** P<0.001) in the length of flagellar tip completely surrounded by the cell body plasma membrane is observed with respect to flagellum length (n≥4 for each position). Scale bars: ∼500 nm.
Mentions: Morphogenetic characteristics of the groove were investigated using SBF-SEM. The technique provides 3D data from large numbers of whole cells at slightly lower resolution than tomography. Volumes containing adjacent serial sections (100-nm thick) of individual trypanosomes with a new flagellum of different lengths were extracted from SBF-SEM datasets and modeled. The morphology was comparable to that obtained by conventional SEM (compare Fig. 5A–C and Fig. 1A,B) and also revealed the internal ultrastructure of the cells. This technique permitted unequivocal identification of the distal tip of the new flagellum and full three-dimensional analysis of the cells and the groove. Analysis of cells with a very short new flagellum that had just exited the flagellar pocket demonstrated that the groove was first located at the point where the distal tip of the new flagellum exited the flagellar pocket. This is best illustrated by viewing supplementary material Movie 4 of the cell shown in Fig. 5A. A groove was observed in all whole-cell reconstructions where the cell possessed a new flagellum that had exited the flagellar pocket, but had not reached the anterior end of the cell. This is best illustrated by viewing supplementary material Movie 5 of the cell imaged in Fig. 5B. In cells where the new flagellum had extended to the anterior end of the cell but had not extended beyond it, a groove structure was evident. However, in cells where the new flagellum was beyond the anterior tip of the cell (Fig. 5C) or had begun cytokinesis no groove was observed.

Bottom Line: We suggest that the groove has a similar function to the flagella connector.The groove is a mobile junction located alongside the microtubule quartet (MtQ) and occurred within a gap in the subpellicular microtubule corset, causing significant modification of microtubules during elongation of the new flagellum.It appears likely that this novel form of morphogenetic structure has evolved to withstand the hostile immune response in the mammalian blood.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological and Medical Sciences, Faculty of Health and Life Science, Oxford Brookes University, Oxford OX3 0BP, UK.

ABSTRACT
Flagella are highly conserved organelles present in a wide variety of species. In Trypanosoma brucei the single flagellum is necessary for morphogenesis, cell motility and pathogenesis, and is attached along the cell body. A new flagellum is formed alongside the old during the cell division cycle. In the (insect) procyclic form, the flagella connector (FC) attaches the tip of the new flagellum to the side of the old flagellum, ensuring faithful replication of cell architecture. The FC is not present in the bloodstream form of the parasite. We show here, using new imaging techniques including serial block-face scanning electron microscopy (SBF-SEM), that the distal tip of the new flagellum in the bloodstream form is embedded within an invagination in the cell body plasma membrane, named the groove. We suggest that the groove has a similar function to the flagella connector. The groove is a mobile junction located alongside the microtubule quartet (MtQ) and occurred within a gap in the subpellicular microtubule corset, causing significant modification of microtubules during elongation of the new flagellum. It appears likely that this novel form of morphogenetic structure has evolved to withstand the hostile immune response in the mammalian blood.

Show MeSH
Related in: MedlinePlus