pyrenoid tubule

GO:0160223 · Membrane organelle · Membrane · Proposed

A specialized membranous structure that extends from the photosynthetic thylakoid membrane into and transverses the matrix of a pyrenoid. [GO:0160223]

Part of: pyrenoid (GO:1990732)

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
pyrenoid tubule lipid bilayer	Lipid	part of	Reviewed label only (reviewed name; no accession asserted)			ESSENTIAL	Generic thylakoid-derived lipid bilayer that forms a membrane tubule traversing the pyrenoid matrix. `GO:0160223` GO:0160223 defines the pyrenoid tubule as a specialized membranous structure extending from the photosynthetic thylakoid membrane into the pyrenoid matrix. `DOI:10.7554/eLife.04889` Engel et al. 2015 resolved pyrenoid-crossing membrane tubules in native Chlamydomonas chloroplasts by in situ cryo-electron tomography.

Taxonomic distribution

NCBITaxon:2759 Eukaryota — RARE: Pyrenoid-traversing membranes occur in pyrenoid-containing photosynthetic eukaryotes, a lineage-restricted subset of Eukaryota. [DOI:10.1111/nph.70669]
NCBITaxon:3055 Chlamydomonas reinhardtii — COMMON: Chlamydomonas reinhardtii has pyrenoid-traversing thylakoid membrane tubules continuous with the surrounding chloroplast thylakoid network. [DOI:10.7554/eLife.04889]

Canonical examples

NCBITaxon:3055 Chlamydomonas reinhardtii — Green alga in which cryo-electron tomography resolved parallel minitubules inside pyrenoid tubules. [DOI:10.7554/eLife.04889]

Functions

pyrenoid inorganic carbon delivery — Pyrenoid tubules are thylakoid-membrane continuities that traverse the Rubisco-rich pyrenoid matrix and are thought to support delivery of concentrated inorganic carbon to the pyrenoid.
- DOI:10.1093/plcell/koad157 He, Crans and Jonikas 2023 review the pyrenoid as a eukaryotic CO2-concentrating organelle whose matrix is traversed by membranes in many lineages.
- DOI:10.1111/nph.70669 Franklin et al. 2026 describe pyrenoid-traversing membranes as membranes thought to supply concentrated CO2 to pyrenoids.

Mechanism graphs

Pyrenoid tubules traverse the Rubisco matrix (FUNCTION)

Pyrenoid tubules are specialized thylakoid-derived membranes continuous with the chloroplast thylakoid network and traversing the pyrenoid matrix.

Subject	Predicate	Object	Evidence
pyrenoid tubule	is part of	pyrenoid	`GO:0160223` GO:0160223 identifies the pyrenoid tubule as a membranous structure that extends into the matrix of a pyrenoid. `DOI:10.1093/plcell/koad157` He, Crans and Jonikas 2023 review pyrenoid ultrastructure and matrix-traversing membranes.
pyrenoid tubule	is continuous with	thylakoid membrane	`GO:0160223` GO:0160223 defines pyrenoid tubules as extending from the photosynthetic thylakoid membrane. `DOI:10.7554/eLife.04889` Engel et al. 2015 resolved native Chlamydomonas pyrenoid tubules continuous with stromal thylakoids.
pyrenoid tubule	traverses	pyrenoid matrix	`GO:0160223` GO:0160223 defines the pyrenoid tubule by its extension into and traversal across a pyrenoid matrix. `DOI:10.1111/nph.70669` Franklin et al. 2026 enriched and proteomically analyzed Chlamydomonas pyrenoid-traversing membranes.

Discussions

CURATION_TODO (OPEN): Resolve an exact source-neutral grounding for the lipid constituent of the pyrenoid tubule. The record is exactly grounded to GO:0160223, but no exact source-neutral lipid CURIE was curated for the generic constituent of this specialized thylakoid-derived membrane.
INTERPRETATION (RESOLVED): Keep pyrenoid tubules as a standalone exact record rather than a mandatory part of every pyrenoid. GO:0160223 exactly denotes matrix-traversing pyrenoid tubules, but the existing broad pyrenoid record cannot assert them as universal parts because pyrenoid ultrastructure varies among lineages.

Evidence

GO:0160223 Gene Ontology cellular-component term for the pyrenoid tubule.
GO:0016020 Gene Ontology cellular-component parent term for membrane.
GO:1990732 Gene Ontology cellular-component term for the pyrenoid.
GO:0042651 Gene Ontology cellular-component term for thylakoid membrane.
DOI:10.7554/eLife.04889 Engel et al. 2015, Native architecture of the Chlamydomonas chloroplast revealed by in situ cryo-electron tomography, eLife.
DOI:10.1093/plcell/koad157 He, Crans, and Jonikas 2023, The pyrenoid: the eukaryotic CO2-concentrating organelle, Plant Cell.
DOI:10.1111/nph.70669 Franklin et al. 2026, Proteomic analysis of the pyrenoid-traversing membranes of Chlamydomonas reinhardtii reveals novel components, New Phytologist.

Curation history

2026-09-13T13:45:26Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-13T13:46:04Z codex · EXPANDED_RECORD — Added membrane parentage, pyrenoid parthood, a label-only pyrenoid-tubule lipid-bilayer component, Eukaryota/Chlamydomonas scope, an inorganic-carbon-delivery function, GO/DOI evidence, a nonmechanistic pyrenoid-tubule topology graph, a lipid-grounding TODO, and a resolved tubule-presence interpretation.
2026-09-13T13:49:50Z codex · FIXED_GROUNDING_LABEL — Aligned the GO:0042651 causal-graph node label with the GO canonical label.

Source: data/structures/membrane_organelle/pyrenoid_tubule.yaml