mononeme

GO:0070074 · Membrane organelle · Membrane bounded organelle · Proposed

A small, threadlike secretory organelle that forms part of the apical complex and lies close to the subpellicular microtubules. [GO:0070074]

Part of: apical complex (GO:0020007)

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
PfROM1 rhomboid-1 protease	Protein	part of	Reviewed label only (reviewed name; no accession asserted)	PfROM1		UNKNOWN	Plasmodium falciparum rhomboid-1 protease that resides in the mononeme before merozoite release and redistributes to the merozoite surface with apical and posterior enrichment after release. `DOI:10.1073/pnas.0709999104` Singh et al. 2007 identified PfROM1 as a rhomboid protease in the newly named mononeme and followed its redistribution after merozoite release.

Taxonomic distribution

NCBITaxon:5833 Plasmodium falciparum — COMMON: Mononemes are directly evidenced in mature Plasmodium falciparum segmenter-stage merozoites; released merozoites are cited only as evidence for PfROM1 redistribution after leaving the mononeme. [DOI:10.1073/pnas.0709999104]

Canonical examples

NCBITaxon:5833 Plasmodium falciparum — Human malaria parasite in which HA-tagged PfROM1 revealed a single thread-like mononeme running along one side of mature segmenter-stage merozoites close to the subpellicular microtubules. [DOI:10.1073/pnas.0709999104]

Functions

rhomboid-1 compartmentalization — The mononeme stores PfROM1 in a compartment distinct from micronemes, rhoptries and dense granules in mature Plasmodium falciparum merozoites, before PfROM1 redistributes to the merozoite surface after erythrocyte rupture.
- DOI:10.1073/pnas.0709999104 Singh et al. 2007 separated PfROM1 from microneme, rhoptry and dense-granule markers and proposed that mononeme sequestration keeps PfROM1 apart from micronemal substrates before merozoite release.

Mechanism graphs

PfROM1 marks a threadlike mononeme before merozoite release (FUNCTION)

PfROM1 resides in the single thread-like mononeme next to the subpellicular microtubules in mature P. falciparum merozoites; after erythrocyte rupture, PfROM1 redistributes to the merozoite surface with apical and posterior enrichment.

Subject	Predicate	Object	Evidence
PfROM1 rhomboid-1 protease	resides in	mononeme	`DOI:10.1073/pnas.0709999104` Singh et al. 2007 localized HA-PfROM1 to a single thread-like structure in mature P. falciparum segmenters and named that organelle the mononeme.
mononeme	lies close to	subpellicular microtubule	`DOI:10.1073/pnas.0709999104` Singh et al. 2007 found HA-PfROM1 in close proximity to the longitudinal subpellicular microtubules. `GO:0070074` Gene Ontology defines the mononeme as a thread-like apical-complex organelle located close to the subpellicular microtubules.
mononeme	is distinct from	microneme	`DOI:10.1073/pnas.0709999104` Singh et al. 2007 found that HA-PfROM1 did not colocalize with the AMA1 microneme marker.
mononeme	is distinct from	rhoptry	`DOI:10.1073/pnas.0709999104` Singh et al. 2007 found that HA-PfROM1 did not colocalize with rhoptry neck or rhoptry bulb markers.
mononeme	is distinct from	apicomplexan dense granule	`DOI:10.1073/pnas.0709999104` Singh et al. 2007 found that HA-PfROM1 did not colocalize with a RESA dense-granule marker.
PfROM1 rhomboid-1 protease	redistributes to	post-release merozoite surface	`DOI:10.1073/pnas.0709999104` Singh et al. 2007 tracked HA-PfROM1 relocalization to apical and posterior poles after merozoite release.

Discussions

CURATION_TODO (OPEN): Resolve the mononeme membrane boundary and any conserved cargo or accessory proteins beyond PfROM1. The first mononeme paper establishes PfROM1 localization in a distinct thread-like apical organelle, but this record does not yet curate an exact mononeme membrane, lumen, motor, or pan-apicomplexan cargo cohort.
INTERPRETATION (RESOLVED): Avoid asserting a microtubule-based mononeme transport mechanism until direct motor or route evidence is curated. Singh et al. noted that the mononeme might move along microtubules and that testing this would require exact localization of the mononeme and candidate motors. The causal graph therefore records only observed topology and PfROM1 relocalization.

Evidence

GO:0070074 Gene Ontology cellular-component term for the mononeme.
GO:0043231 Gene Ontology places mononemes under intracellular membrane-bounded organelles.
GO:0020007 Gene Ontology models mononemes as part of the apical complex.
DOI:10.1073/pnas.0709999104 Singh et al. 2007, Mononeme: A new secretory organelle in Plasmodium falciparum merozoites identified by localization of rhomboid-1 protease, Proceedings of the National Academy of Sciences of the United States of America.

Curation history

2026-09-22T12:33:57Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-22T12:35:28Z codex · EXPANDED_RECORD — Added GO apical-complex parentage, PfROM1 as a reviewed label-only component, Plasmodium falciparum scope, DOI/GO evidence, a nonmechanistic PfROM1 relocalization graph, and curation discussions for unresolved mononeme boundaries and microtubule-motor restraint.
2026-09-22T12:36:12Z codex · FIXED_CITATION_METADATA — Corrected the Singh et al. 2007 mononeme citation title and journal.
2026-09-22T12:49:02Z codex · ADDRESSED_REVIEW — Addressed PR #1280 review issues #1281 and #1282 by narrowing the P. falciparum taxonomic note to pre-release segmenter mononeme evidence and adding rhoptry and dense-granule distinctness edges to the PfROM1 relocalization graph.
2026-09-22T12:49:36Z codex · TIGHTENED_CANONICAL_SCOPE — Narrowed the Plasmodium falciparum canonical example to segmenter-stage merozoites for consistency with PR #1280 review issue #1281.

Source: data/structures/membrane_organelle/mononeme.yaml