cyanelle

GO:0009842 · Membrane organelle · Membrane bounded organelle · Proposed

A plastid that contains unstacked, phycobilisome-bearing thylakoid membranes and is surrounded by a double membrane with a peptidoglycan layer in the intermembrane space between the two envelope membranes. Cyanelles are characteristic of algae in the class Glaucophyta, and may represent an ancestral form of plastid. [GO:0009842]

Synonyms: cyanoplast; muroplast

Has part: cyanelle envelope (GO:0033112); cyanelle inner membrane (GO:0036012); cyanelle outer membrane (GO:0036013); cyanelle intermembrane space (GO:0036014); cyanelle stroma (GO:0034060); cyanelle thylakoid (GO:0009843); cyanelle thylakoid lumen (GO:0033114); cyanelle thylakoid membrane (GO:0033115)

Xrefs: uniprot.location:SL-0082 — Cyanelle

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

Components

Component	Type	Part of / acts on	Grounding	Essential	Role
cyanelle outer membrane	Lipid	part of	`GO:0036013`	UNKNOWN	Cytoplasm-facing lipid bilayer of the double cyanelle envelope. `GO:0036013` GO:0036013 defines the cyanelle outer membrane as the cytoplasm-facing lipid bilayer of the cyanelle envelope. `DOI:10.1074/jbc.M116.746131` Kojima et al. 2016 studied Cyanophora paradoxa outer cyanelle membrane proteins positioned outside the peptidoglycan layer.
cyanelle inner membrane	Lipid	part of	`GO:0036012`	UNKNOWN	Stroma-facing lipid bilayer of the cyanelle envelope. `GO:0036012` GO:0036012 defines the cyanelle inner membrane as the lumen-facing cyanelle envelope membrane.
cyanelle thylakoid membrane	Lipid	part of	`GO:0033115`	UNKNOWN	Internal photosynthetic membrane of the cyanelle thylakoid system. `GO:0033115` GO:0033115 defines the cyanelle thylakoid membrane as the lipid bilayer of thylakoids inside a cyanelle. `DOI:10.1104/pp.71.2.409` Giddings et al. 1983 characterized Cyanophora paradoxa cyanelle thylakoid and envelope membrane ultrastructure.
cyanelle peptidoglycan layer	Peptidoglycan	part of	Reviewed label only (reviewed name; no accession asserted)	UNKNOWN	Peptidoglycan wall-like layer retained between the inner and outer membranes of the cyanelle envelope. `GO:0036014` GO:0036014 defines the cyanelle intermembrane space as including the peptidoglycan layer. `DOI:10.1128/jb.178.2.332-339.1996` Pfanzagl et al. 1996 characterized Cyanophora paradoxa cyanelle peptidoglycan as a prokaryotic cell wall retained within an organelle envelope.

Taxonomic distribution

NCBITaxon:38254 Glaucocystophyceae — COMMON: Glaucophytes are Archaeplastida whose plastids retain cyanobacteria-associated traits including peptidoglycan and phycobilisomes. [PMID:31098614]
NCBITaxon:2762 Cyanophora paradoxa — COMMON: Cyanophora paradoxa is a glaucophyte model whose cyanelles have double envelopes, thylakoids, and cyanelle peptidoglycan. [DOI:10.1128/jb.178.2.332-339.1996]

Canonical examples

NCBITaxon:2762 Cyanophora paradoxa — Model glaucophyte used for ultrastructural and biochemical studies of cyanelle thylakoids, envelope membranes, and peptidoglycan. [DOI:10.1104/pp.71.2.409]

Functions

photosynthesis GO:0015979 — Cyanelle thylakoid membranes house photosynthetic machinery in the glaucophyte plastid.
- GO:0009842 GO:0009842 defines the cyanelle as a plastid with phycobilisome-bearing thylakoid membranes.
- PMID:31098614 Price et al. 2019 describe peptidoglycan and phycobilisomes as retained cyanobacterial plastid traits in glaucophytes.

Mechanism graphs

Cyanelle envelope and thylakoid topology (FUNCTION)

The cyanelle is bounded by inner and outer envelope membranes with peptidoglycan in the intermembrane space, and it carries internal thylakoid membranes for photosynthesis.

Subject	Predicate	Object	Evidence
cyanelle outer membrane	bounds	cyanelle	`GO:0036013` GO:0036013 defines the cyanelle outer membrane as the cytoplasm-facing envelope membrane.
cyanelle inner membrane	bounds	cyanelle stroma	`GO:0036012` GO:0036012 defines the cyanelle inner membrane as the envelope bilayer that faces the cyanelle stroma.
cyanelle peptidoglycan layer	resides in	cyanelle intermembrane space	`GO:0036014` GO:0036014 defines the cyanelle intermembrane space as including the peptidoglycan layer. `DOI:10.1128/jb.178.2.332-339.1996` Pfanzagl et al. 1996 biochemically characterized Cyanophora paradoxa cyanelle peptidoglycan.
cyanelle thylakoid membrane	is part of	cyanelle thylakoid	`GO:0033115` GO:0033115 defines the cyanelle thylakoid membrane as the bilayer of cyanelle thylakoids.
cyanelle thylakoid membrane	supports	photosynthesis	`GO:0009842` GO:0009842 defines cyanelles as plastids with phycobilisome-bearing thylakoid membranes. `PMID:31098614` Price et al. 2019 describe peptidoglycan and phycobilisomes as retained cyanobacterial plastid traits in glaucophytes.

Discussions

CURATION_TODO (OPEN): Resolve an exact source-neutral grounding for the peptidoglycan layer in the cyanelle intermembrane space. GO provides exact terms for the cyanelle intermembrane space and the envelope membranes, while the peptidoglycan layer itself is represented as a reviewed-label component backed by biochemical evidence.

Evidence

GO:0009842 Gene Ontology cellular-component term for cyanelle.
GO:0009536 Gene Ontology cellular-component term for plastid.
GO:0033112 Gene Ontology cellular-component term for cyanelle envelope.
GO:0036012 Gene Ontology cellular-component term for cyanelle inner membrane.
GO:0036013 Gene Ontology cellular-component term for cyanelle outer membrane.
GO:0036014 Gene Ontology cellular-component term for cyanelle intermembrane space.
GO:0034060 Gene Ontology cellular-component term for cyanelle stroma.
GO:0009843 Gene Ontology cellular-component term for cyanelle thylakoid.
GO:0033114 Gene Ontology cellular-component term for cyanelle thylakoid lumen.
GO:0033115 Gene Ontology cellular-component term for cyanelle thylakoid membrane.
uniprot.location:SL-0082 — Cyanelle UniProt Subcellular Location entry SL-0082 maps Cyanelle to GO:0009842.
DOI:10.1104/pp.71.2.409 Giddings, Wasmann and Staehelin 1983, Structure of the Thylakoids and Envelope Membranes of the Cyanelles of Cyanophora paradoxa, Plant Physiology.
DOI:10.1128/jb.178.2.332-339.1996 Pfanzagl et al. 1996, Primary structure of cyanelle peptidoglycan of Cyanophora paradoxa: a prokaryotic cell wall as part of an organelle envelope, Journal of Bacteriology.
DOI:10.1074/jbc.M116.746131 Kojima, Muramoto and Kusano 2016, Outer Membrane Proteins Derived from Non-cyanobacterial Lineage Cover the Peptidoglycan of Cyanophora paradoxa Cyanelles and Serve as a Cyanelle Diffusion Channel, Journal of Biological Chemistry.
PMID:31098614 Price et al. 2019, Analysis of an improved Cyanophora paradoxa genome assembly, DNA Research.

Curation history

2026-09-12T15:33:30Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-12T15:34:39Z codex · EXPANDED_RECORD — Added plastid parentage, exact cyanelle membrane, stroma and thylakoid part terms, GO synonyms, the UniProt Subcellular Location xref, membrane and peptidoglycan components, Glaucocystophyceae and Cyanophora paradoxa scope, a photosynthesis function, a cyanelle topology graph, and a peptidoglycan-layer grounding TODO.
2026-09-12T15:45:14Z codex · ADDRESS_REVIEW — Resolved #668 by adding a cyanelle stroma node and retargeting the inner-membrane boundary edge to the stroma. Resolved #669 by replacing ultrastructure-only photosynthesis evidence with GO and Jackson et al. 2015 support.
2026-09-21T10:04:10Z codex · REPLACED_UNREADABLE_EVIDENCE — Replaced unreadable Jackson et al. 2015 Glaucophyta evidence with reachable cyanelle evidence for #1231.

Source: data/structures/membrane_organelle/cyanelle.yaml