prospore membrane

GO:0005628 · Spore · Membrane · Proposed

An ascospore-forming fungal double-membrane structure that grows from meiotic outer plaques to encapsulate meiotic nuclei and provide the foundation for spore-wall assembly. [GO:0005628]

Synonyms: ascospore-type prospore membrane; FSM; forespore membrane

Part of: GO:0042764 — ascospore-type prospore (no local record)

Has part: prospore membrane leading edge (GO:0070056); prospore membrane spindle pole body attachment site (GO:0070057)

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
prospore membrane lipid bilayer	Lipid	part of				ESSENTIAL	Double membrane that expands from the meiotic spindle-pole body region and surrounds haploid nuclei during ascospore formation. `GO:0005628` GO:0005628 defines the prospore membrane as a double-membraned structure that extends from the cytoplasmic face of spindle pole bodies during meiosis. `DOI:10.1083/jcb.140.1.29` Neiman 1998 analyzed prospore membrane formation in Saccharomyces cerevisiae as a sporulation-specific branch of post-Golgi secretion.
prospore membrane leading edge protein coat	Protein complex	part of	Reviewed label only (reviewed name; no accession asserted)	SSP1, ADY3, DON1		UNKNOWN	Protein coat at the lip of the growing prospore membrane that marks the leading edge before membrane closure. `GO:0070056` GO:0070056 defines the prospore membrane leading edge as the protein-coated region that extends to surround the spore nucleus. `DOI:10.1093/emboj/20.24.6946` Moreno-Borchart et al. 2001 linked formation of the Saccharomyces prospore membrane to leading-edge protein coat assembly.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast builds prospore membranes during the sporulation program; this species-level scope avoids asserting conservation of the membrane or leading-edge protein set across all ascospore-forming fungi. [DOI:10.1083/jcb.140.1.29]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model in which secretory trafficking, meiotic outer plaques, and leading-edge coat proteins were tied to prospore membrane assembly. [DOI:10.1093/emboj/20.24.6946]

Functions

ascospore-type prospore assembly GO:0031321 — Expansion and closure of the prospore membrane encapsulate haploid meiotic nuclei to create immature ascospores.
- GO:0031321 GO:0031321 defines ascospore-type prospore assembly as the encapsulation of each haploid nucleus by a double membrane.

Mechanism graphs

Secretory traffic and the leading edge build the prospore membrane (ASSEMBLY)

During budding-yeast sporulation, post-Golgi secretory traffic supplies membrane at meiotic outer plaques to generate prospore membranes, while leading-edge coat proteins track the open rim of the growing membrane before closure.

Subject	Predicate	Object	Evidence
post-Golgi secretory vesicles	supplies membrane for	prospore membrane	`DOI:10.1083/jcb.140.1.29` Neiman 1998 found that late secretory SEC1, SEC4 and SEC8 function is required for prospore membrane formation in Saccharomyces cerevisiae.
meiotic outer plaque	anchors initiation of	prospore membrane	`DOI:10.1093/emboj/19.14.3657` Knop and Strasser 2000 studied the spindle-pole-body role in assembling prospore membranes during meiosis. `GO:0032120` GO:0032120 defines prospore membrane formation as nascent membrane growth from the meiotic outer plaque.
prospore membrane leading edge protein coat	localizes to	prospore membrane leading edge	`DOI:10.1093/emboj/20.24.6946` Moreno-Borchart et al. 2001 tied LEP coat assembly to formation of the growing prospore membrane. `GO:0070056` GO:0070056 describes a protein-coated leading-edge region on the prospore membrane.
prospore membrane	encapsulates	haploid meiotic nucleus	`GO:0005628` GO:0005628 defines the prospore membrane as encompassing the nuclear lobes formed during meiosis. `GO:0031321` GO:0031321 defines ascospore-type prospore assembly as encapsulation of each haploid nucleus by a double membrane.

Discussions

CURATION_TODO (OPEN): Resolve exact source-neutral groundings and component boundaries for the prospore membrane leading-edge coat subunits. The initial record treats the leading-edge coat as one reviewed-label-only constituent and records Saccharomyces SSP1, ADY3 and DON1 as gene-symbol metadata. Exact family groundings for individual Ssp1, Ady3, Don1 and Irc10 components, and the boundary between stable coat proteins and Spo20/Sso1 fusion machinery, need a focused curation pass.
CURATION_TODO (RESOLVED): Should the meiotic spindle pole body or meiotic outer plaque be modeled as a prospore membrane component? The meiotic outer plaque nucleates and anchors prospore membrane formation, but it is a specialization of the spindle pole body rather than a molecular constituent of the membrane itself.

Evidence

GO:0005628 Gene Ontology cellular-component term for the prospore membrane.
GO:0042764 — ascospore-type prospore Gene Ontology cellular-component term for the ascospore-type prospore that has the prospore membrane as a part.
GO:0070056 Gene Ontology cellular-component term for the prospore membrane leading edge.
GO:0070057 Gene Ontology cellular-component term for the prospore membrane spindle pole body attachment site.
GO:0032120 Gene Ontology biological-process term for ascospore-type prospore membrane formation.
GO:0031321 Gene Ontology biological-process term for ascospore-type prospore assembly.
DOI:10.1083/jcb.140.1.29 Neiman 1998, Prospore Membrane Formation Defines a Developmentally Regulated Branch of the Secretory Pathway in Yeast, Journal of Cell Biology.
DOI:10.1093/emboj/19.14.3657 Knop and Strasser 2000, Role of the spindle pole body of yeast in mediating assembly of the prospore membrane during meiosis, The EMBO Journal.
DOI:10.1093/emboj/20.24.6946 Moreno-Borchart et al. 2001, Prospore membrane formation linked to the leading edge protein (LEP) coat assembly, The EMBO Journal.

Curation history

2026-09-12T09:20:45Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-12T09:21:47Z codex · EXPANDED_RECORD — Added exact and related GO synonymy, membrane parentage, ascospore-type prospore parthood, GO leading-edge and attachment-site parts, lipid bilayer and leading-edge-coat components, Saccharomyces scope, GO-grounded functions, DOI/GO evidence, a nonmechanistic assembly graph, a leading-edge-coat grounding TODO, and an SPB boundary decision.
2026-09-12T09:22:12Z codex · TIGHTENED_MODELING — Retargeted the prospore membrane encapsulation graph edge from the whole ascospore-type prospore to the haploid meiotic nucleus, which the membrane surrounds during ascospore assembly.
2026-09-12T09:30:17Z codex · ADDRESSED_PR_REVIEW — Resolved PR #621 review issues #622 and #623 by removing the self-assembly GO:0032120 process from functions and softening the post-Golgi vesicle graph edge from direct fusion to membrane supply.
2026-09-20T21:51:50Z codex · ADDRESSED_REVIEW — Retyped the prospore membrane leading-edge coat graph node as STRUCTURE.

Source: data/structures/spore/prospore_membrane.yaml