Giardia trophozoite stage- GO terms/localizations/cellular components
Cytoskeletal
Due to the asymmetric nature of the Giardia trophozoite, the following terms are defined spatially as
the trophozoite is viewed from the dorsal side, with the two nuclei dorsal to the ventral disc, and the
ventral disc toward the anterior.
1. ventral disc [1-3] –attachment organelle characterized by a spiral microtubule array and
microtubule-associated structures including the dorsal microribbons and crossbridges.
1. ventral disc lateral crest – fibrillar repetitive structure surrounding the ventral disc
edge.
2. ventral disc overlap zone – overlapping region of ventral disc microtubule array
3. ventral disc microribbons – trilaminar structures extending perpendicularly into the
cytoplasm along the length of ventral disc microtubules.
4. ventral disc crossbridges – structures horizontally linking adjacent microribbons of the
ventral disc.
5. ventral disc microtubules –microtubules of the ventral disc forming a right-handed
spiral conformation.
2. supernumerary microtubule array [2] – a partial left-handed microtubule spiral array that lies
generally dorsal to the main ventral disc microtubule array
3. flagella/cilia [1, 2, 4]
1. left tetrad – set of four basal bodies located to the right of the left nucleus of the
trophozoite when viewed dorsally.
1. left lateral basal body pair
1. left anterior basal body
2. left ventral basal body
2. left middle basal body pair
1. left caudal basal body
2. left posteriolateral basal body
2. right tetrad - set of four basal bodies located to the left of the right nucleus of the
trophozoite when viewed dorsally.
1. right lateral basal body pair
1. right anterior basal body
2. right ventral basal body
2. right middle basal body pair
1. right caudal basal body
2. right posteriolateral basal body
3. left anterior flagellum – originates at the left anterior basal body, extends laterally through
the cytoplasm, crosses the right anterior axoneme, and exits as a membrane-bound
flagellum on the anterior left side of the cell.
1. left anterior basal body – basal body nucleating the left anterior flagellum.
2. left anterior axoneme transition zone – portion of the left anterior axoneme proximal
to the left anterior basal body
3. left anterior cytoplasmic axoneme – non-membrane bound, cytoplasmic portion of the
left anterior axoneme.
4. left anterior membrane-bound axoneme – extracellular, membrane-bound portion of
the left anterior flagellum.
5. left anterior flagellar pore – structure surrounding the left anterior cytoplasmic
axoneme where it exits the cell body; defines the transition from the left anterior
cytoplasmic axoneme and the left anterior membrane-bound flagellum.
4. right anterior flagellum - originates at the right anterior basal body, extends laterally
through the cytoplasm, crosses the left anterior axoneme, and exits as a membrane-bound
flagellum on the anterior right side of the cell
1. right anterior basal body– basal body nucleating the right anterior flagellum
2. right anterior axoneme transition zone – portion of the right anterior axoneme
proximal to the right anterior basal body
3. right anterior cytoplasmic axoneme – non-membrane bound, cytoplasmic portion of
the right anterior axoneme.
4. right anterior membrane bound axoneme – extracellular, membrane-bound portion of
the right anterior flagellum
5. right anterior flagellar pore – structure surrounding the right anterior cytoplasmic
axoneme where it exits the cell body; defines the transition from the right anterior
cytoplasmic axoneme and the right anterior membrane-bound flagellum.
5. left posteriolateral flagellum – nucleated by the left posteriolateral basal body and extends
cytoplasmically toward the cell posterior, marking the left anterior boundary of the lateral
shield and the left lateral region of the funis before exiting at the left lateral region of the
cell body
1. left posteriolateral basal body– basal body nucleating the left posteriolateral flagellum.
2. left posteriolateral axoneme transition zone– portion of the left posteriolateral
axoneme proximal to the left posteriolateral basal body
3. left posteriolateral cytoplasmic axoneme – non-membrane bound, cytoplasmic portion
of the left posteriolateral axoneme.
4. left posteriolateral membrane-bound axoneme– extracellular, membrane-bound
portion of the left posteriolateral flagellum
5. left posteriolateral flagellar pore – structure surrounding the left posteriolateral
cytoplasmic axoneme where it exits the cell body; defines the transition from the left
posteriolateral cytoplasmic axoneme and the left posteriolateral membrane-bound
flagellum.
6. right posteriolateral flagellum – nucleated by the right posteriolateral basal body and
extends cytoplasmically toward the cell posterior, marking the right anterior boundary of
the lateral shield and the right lateral region of the funis before exiting at the right lateral
region of the cell body
1. right posteriolateral basal body– basal body nucleating the right posteriolateral
flagellum.
2. right posteriolateral axoneme transition zone – portion of the right posteriolateral
axoneme proximal to the right posteriolateral basal body
3. right posteriolateral cytoplasmic axoneme – non-membrane bound, cytoplasmic
portion of the right posteriolateral axoneme
4. right posteriolateral membrane bound axoneme – extracellular, membrane-bound
portion of the right posteriolateral flagellum
5. right posteriolateral flagellar pore– structure surrounding the right posteriolateral
cytoplasmic axoneme where it exits the cell body; defines the transition from the right
posteriolateral cytoplasmic axoneme and the right posteriolateral membrane-bound
flagellum.
7. left ventral flagellum – nucleated by the left ventral basal body exits the cell body
proximally and dorsal to the ventral disc.
1. left ventral basal body– basal body that nucleates the left ventral flagellum.
2. left ventral axoneme transition zone – portion of the left ventral axoneme proximal to
the left ventral basal body
3. left ventral cytoplasmic axoneme – non-membrane bound, cytoplasmic portion of the
left ventral axoneme
4. left ventral membrane bound axoneme – extracellular, membrane-bound portion of the
left ventral flagellum
5. left ventral flagellar pore– structure surrounding the left ventral cytoplasmic axoneme
where it exits the cell body; defines the transition from the left ventral cytoplasmic
axoneme and the left ventral membrane-bound flagellum.
8. right ventral flagellum– nucleated by the right ventral basal body exits the cell body
proximally and dorsal to the ventral disc.
1. right ventral flagella basal body– basal body that nucleates the right ventral flagellum.
2. right ventral axoneme transition zone – portion of the right ventral axoneme proximal
to the right ventral basal body
3. right ventral cytoplasmic axoneme – non-membrane bound, cytoplasmic portion of the
right ventral axoneme
4. right ventral membrane bound axoneme – extracellular, membrane-bound portion of
the right ventral flagellum
5. right ventral flagellar pore– structure surrounding the right ventral cytoplasmic
axoneme where it exits the cell body; defines the transition from the right ventral
cytoplasmic axoneme and the right ventral membrane-bound flagellum.
9. left caudal flagellum – nucleated by the left caudal basal body, extending cytoplasmically
and exiting at the posterior end of the cell body
1. left caudal basal body– basal body which nucleates the left caudal flagella.
2. left caudal axoneme microtubule root – region of basal body nucleating the ventral
disc.
3. left caudal axoneme transition zone – portion of the left caudal axoneme proximal to
the left caudal basal body
4. left caudal cytoplasmic axoneme – non-membrane bound, cytoplasmic portion of the
left caudal axoneme
5. left caudal membrane bound axoneme– extracellular, membrane-bound portion of the
left caudal flagellum
6. left caudal flagellar pore– structure surrounding the left caudal cytoplasmic axoneme
where it exits the cell body; defines the transition from the left caudal cytoplasmic
axoneme and the left caudal membrane-bound flagellum.
10. right caudal flagellum – nucleated by the right caudal basal body, extending cytoplasmically
and exiting at the posterior end of the cell body
1. right caudal flagella basal body– basal body which nucleates the right caudal flagella.
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2. right caudal microtubule root
3. right caudal axoneme transition zone– portion of the right caudal axoneme proximal to
the right caudal basal body
4. right caudal cytoplasmic axoneme – non-membrane bound, cytoplasmic portion of the
right caudal axoneme
5. right caudal membrane bound axoneme– extracellular, membrane-bound portion of
the right caudal flagellum
6. right caudal flagellar pore– structure surrounding the right caudal cytoplasmic axoneme
where it exits the cell body; defines the transition from the right caudal cytoplasmic
axoneme and the right caudal membrane-bound flagellum.
caudal complex / funis [2, 5] – ventral and dorsal microtubule sheets (funis) and associated
structures surrounding the caudal axonemes that also includes the central microtubules
located between the caudal axonemes. This complex begins between the two nuclei near the
basal bodies, and extends to the caudal flagellar pores
median body (also parabasal body) [1]– the non-membrane bound, semi-organized
microtubule array of unknown function present on the dorsal side of a trophozoite, slightly
posterior to the ventral disc.
marginal plate [2, 6] – two striated lamellae originating at the left and right anterior basal
bodies, that associate with the cytoplasmic regions of the right and left anterior axonemes.
1. left anterior marginal plate - striated lamellae associated with the cytoplasmic axoneme
region of the left anterior flagellum; originates at the left anterior basal body.
2. right anterior marginal plate - striated lamellae associated with the cytoplasmic axoneme
region of the right anterior flagellum; originates at the right anterior basal body.
striated fibers [2] – striated fibers originating at both the left and right anterior basal bodies
that extend anteriorly from the curved cytoplasmic regions of the right and left anterior
axonemes
1. left anterior flagella striated fiber
2. right anterior flagella striated fiber
Other
1. marginal groove [1, 2] – open channel in the anterior ventral plasma membrane lying between
the lateral crest and the ventrolateral flange
2. ventrolateral flange [1] [2]– edge of the anterior ventral plasma membrane that surrounds the
lateral margins of the ventral disc .
3. lateral shield [2]– regions of the ventral side of the cell body posterior on either side of the
ventral groove; the upper boundary is the ventral disc, and the lower boundary is marked by
the posteriolateral flagella.
4. ventral groove [2]– ventral channel dorsal to the ventral disc where the membrane bound
regions of the ventral flagella exit and extend. This regions is demarcated by the cytoplasmic
regions of the posteriolateral axonemes before they exit the trophozoite cell body.
5. peripheral vesicles [7]- flattened vacuoles present close to the dorsal plasma membrane.
6. bare area vesicles [7]– vesicles located in the bare area region of the ventral plasma
membrane.
7. encystation specific vesicles (ESV) [8]– cytoplasmic vesicles that transport cyst wall protein to
the cell membrane prior to encystation
8. cyst wall [8]– a proteinaceous wall surrounding the plasma membrane in the cyst form.
9. mitosomes [9]– cytoplasmic vesicles sometimes present between to the nuclei
10. fimbrae [2] –finger-like projections of the ventral plasma membrane
11. left nucleus [7]– the nucleus on the left side of the cell when viewed from the dorsal side
12. right nucleus [7]– the nucleus on the right side of the cell when viewed from the dorsal side
References
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