median body

GO:0097568 · Cytoskeleton · Other · Proposed

A non-membrane bound, semi-organized microtubule array of unknown function found in Giardia species (trophozoite stage). It is located on the dorsal side of the trophozoite, slightly posterior to the ventral disc. [GO:0097568]

Synonyms: parabasal body

Part of: GO:0005856 — cytoskeleton (no local record)

Has part: microtubule (GO:0005874)

UniProt location names: UniProt Consortium, CC BY 4.0. Reference label and route sources.

Components

Component	Type	Part of / acts on	Grounding	Genes	Stoichiometry	Essential	Role
alpha- and beta-tubulins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Tubulin constituents that polymerize into the Giardia median-body microtubule array. `GO:0005874` Gene Ontology defines microtubules as tubes of polymeric tubulin. `DOI:10.1016/j.biolcel.2004.05.006` Piva and Benchimol 2004 showed that Giardia median-body microtubules react with anti-tubulin antibodies.
Giardia Kinesin-13	Protein	acts on	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Microtubule-dynamics regulator that localizes to the Giardia median body and whose dominant-negative perturbation changes median-body volume. `DOI:10.1128/EC.00128-07` Dawson et al. 2007 localized Giardia Kinesin-13 and EB1 to the median body and observed altered median-body volume after expression of a Kinesin-13 rigor mutant.

Taxonomic distribution

NCBITaxon:5741 Giardia intestinalis — COMMON: Giardia intestinalis trophozoites carry a median-body microtubule array whose ultrastructure and Kinesin-13-associated dynamics have been studied experimentally. [DOI:10.1016/j.biolcel.2004.05.006]

Canonical examples

NCBITaxon:5741 Giardia intestinalis — Diplomonad parasite model in which median-body ultrastructure and Kinesin-13/EB1 localization to the median-body microtubule array were experimentally characterized. [DOI:10.1128/EC.00128-07]

Mechanism graphs

Tubulin microtubules and Kinesin-13 shape the Giardia median body (REGULATION)

In Giardia trophozoites, alpha- and beta-tubulins polymerize into a semi-organized median-body microtubule array. Kinesin-13 and EB1 localize to the median body, and dominant-negative Kinesin-13 changes median-body volume.

Subject	Predicate	Object	Evidence
alpha- and beta-tubulins	polymerize into	microtubule	`GO:0005874` Gene Ontology defines microtubules as polymeric tubulin tubes.
microtubule	assemble into	median body	`GO:0097568` Gene Ontology defines the median body as a semi-organized Giardia microtubule array. `DOI:10.1083/jcb.29.2.317` Friend 1966 observed the Giardia median body as an aggregate of curved microtubules by electron microscopy.
Giardia Kinesin-13	localizes to	median body	`DOI:10.1128/EC.00128-07` Dawson et al. 2007 detected GFP-tagged Kinesin-13 and EB1 at the Giardia median body.
Giardia Kinesin-13	modulates volume of	median body	`DOI:10.1128/EC.00128-07` Dawson et al. 2007 found decreased median-body volume after expression of a Kinesin-13 S280N rigor mutant.

Discussions

CURATION_TODO (OPEN): Resolve exact component boundaries and source-neutral groundings for Giardia median-body tubulins, Kinesin-13, beta-giardin-reactive material, and additional median-body-associated proteins. The median body is a tubulin microtubule array and Kinesin-13/EB1 localize to it, but this pass did not curate exact protein-family boundaries for all alpha/beta tubulins, beta-giardin-reactive material, or regulators associated with this Giardia-specific array.
CURATION_TODO (OPEN): Resolve the cellular function of the Giardia median body before asserting a biological-process function. GO:0097568 explicitly describes the median body as a Giardia microtubule array of unknown function. The first record therefore captures microtubule composition and Kinesin-13-associated dynamics but avoids assigning a specific physiological function.

Evidence

GO:0097568 Gene Ontology cellular-component term for the Giardia median body.
GO:0005856 — cytoskeleton Gene Ontology places the median body under the cytoskeleton.
GO:0005874 Gene Ontology records microtubules as parts of the median body.
DOI:10.1083/jcb.29.2.317 Friend 1966, The fine structure of Giardia muris, Journal of Cell Biology.
DOI:10.1016/j.biolcel.2004.05.006 Piva and Benchimol 2004, The median body of Giardia lamblia: an ultrastructural study, Biology of the Cell.
DOI:10.1128/EC.00128-07 Dawson et al. 2007, Kinesin-13 regulates flagellar, interphase, and mitotic microtubule dynamics in Giardia intestinalis, Eukaryotic Cell.
DOI:10.1016/bs.apar.2019.11.001 Microtubule organelles in Giardia, Advances in Parasitology.

Curation history

2026-09-22T08:43:32Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-22T08:44:44Z codex · EXPANDED_RECORD — Added median-body synonymy, cytoskeleton parthood, a microtubule has_part link, alpha/beta tubulin and Kinesin-13 components, Giardia intestinalis scope, DOI evidence, a nonmechanistic Kinesin-13 dynamics graph, and open TODOs for component boundaries and median-body function.

Source: data/structures/cytoskeleton/median_body.yaml