ascospore wall

GO:0005619 · Spore · Envelope layer · Proposed

The specialized cell wall of the ascospore (spore), which is the product of meiotic division. Examples of this component are found in Fungi. [GO:0005619]

Synonyms: fungal-type spore wall

Has part: inner layer of spore wall (GO:0005632); chitosan layer of spore wall (GO:0005631); dityrosine layer of spore wall (GO:0005630); Isp3 layer of spore wall (GO:1990916)

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

Components

Component	Type	Part of / acts on	Grounding	Essential	Role
ascospore inner-wall mannan and beta-glucan polymers	Polysaccharide	part of	Reviewed label only (reviewed name; no accession asserted)	UNKNOWN	Innermost mannan- and beta-glucan-rich polysaccharide material underneath the chitosan and dityrosine-rich outer layers. `GO:0005632` GO:0005632 identifies the two innermost Saccharomyces spore-wall layers. `DOI:10.1128/MMBR.69.4.565-584.2005` Neiman 2005 reviews assembly of the multilaminar Saccharomyces cerevisiae ascospore wall.
chitosan	Polysaccharide	part of	`CHEBI:16261`	UNKNOWN	Chitosan polymer material in the Saccharomyces ascospore wall, positioned below the dityrosine-rich surface. `CHEBI:16261` ChEBI term for chitosan. `GO:0005631` GO:0005631 identifies the complete chitosan layer as the second outermost Saccharomyces spore-wall layer. `DOI:10.1016/S0014-5793(99)01334-4` Christodoulidou et al. 1999 studied Saccharomyces Cda1/Cda2 chitin deacetylases and their role in ascospore-wall assembly.
ascospore wall dityrosine-rich outer layer	Other	part of	Reviewed label only (reviewed name; no accession asserted)	UNKNOWN	Outermost dityrosine-containing layer of the Saccharomyces ascospore wall that contributes to the resistant spore surface. `GO:0005630` GO:0005630 identifies the dityrosine layer as the outermost Saccharomyces spore-wall layer. `DOI:10.1371/journal.pgen.1003700` Lin et al. 2013 analyzed assembly of the Saccharomyces outer spore wall, including the dityrosine layer.

Taxonomic distribution

NCBITaxon:4932 Saccharomyces cerevisiae — COMMON: Budding yeast builds an ascospore wall around each haploid spore during meiosis and sporulation; this species-level scope avoids asserting that Saccharomyces layer chemistry is identical across all ascospore-forming fungi. [DOI:10.1128/MMBR.69.4.565-584.2005]

Canonical examples

NCBITaxon:4932 Saccharomyces cerevisiae — Budding-yeast model for prospore-membrane closure, spore-wall polymer deposition, and chitosan/dityrosine outer-wall assembly. [DOI:10.1128/MMBR.69.4.565-584.2005]

Functions

ascospore environmental stress barrier — The mature ascospore wall surrounds the spore plasma membrane and protects the dormant spore from environmental stresses.
- DOI:10.1128/MMBR.69.4.565-584.2005 Neiman 2005 reviews the mature Saccharomyces spore wall as a multilaminar wall that provides environmental stress resistance.
- DOI:10.1371/journal.pone.0002873 Coluccio et al. 2008 tested Saccharomyces ascospore survival after passage through the Drosophila digestive tract.

Mechanism graphs

Inner polysaccharides and outer layers build a resistant ascospore wall (ASSEMBLY)

In budding yeast, mannan- and beta-glucan-rich inner layers are covered by a chitosan layer and a dityrosine-rich outer layer to build a multilaminar ascospore wall that surrounds the spore plasma membrane and protects the dormant spore.

Subject	Predicate	Object	Evidence
prospore membrane	templates deposition of	ascospore wall	`GO:0030476` GO:0030476 defines ascospore wall assembly as deposition of wall components in the lumenal space between the outer and inner prospore-membrane leaflets.
ascospore inner-wall mannan and beta-glucan polymers	forms	inner layer of spore wall	`GO:0005632` GO:0005632 denotes either of the two innermost Saccharomyces spore-wall layers. `DOI:10.1128/MMBR.69.4.565-584.2005` Neiman 2005 reviews Saccharomyces ascospore-wall layers and their deposition after prospore-membrane closure.
inner layer of spore wall	is layer of	ascospore wall	`GO:0005632` GO:0005632 defines the inner layer as part of the Saccharomyces spore wall. `GO:0005619` GO places GO:0005632 as part of the ascospore wall.
chitosan	forms	chitosan layer of spore wall	`CHEBI:16261` ChEBI term for chitosan. `GO:0005631` GO:0005631 identifies the complete chitosan layer as the second outermost Saccharomyces spore-wall layer. `DOI:10.1128/MMBR.69.4.565-584.2005` Neiman 2005 reviews chitosan as the Saccharomyces ascospore-wall layer beneath the dityrosine layer.
chitosan layer of spore wall	overlies	inner layer of spore wall	`GO:0005631` GO:0005631 defines the chitosan layer as the second outermost Saccharomyces spore-wall layer. `GO:0005632` GO:0005632 defines the inner layers as the two innermost Saccharomyces spore-wall layers.
ascospore wall dityrosine-rich outer layer	overlies	chitosan layer of spore wall	`GO:0005630` GO:0005630 defines the dityrosine layer as the outermost Saccharomyces spore-wall layer. `GO:0005631` GO:0005631 places the chitosan layer immediately under the outermost Saccharomyces dityrosine layer. `DOI:10.1371/journal.pgen.1003700` Lin et al. 2013 studied genes controlling Saccharomyces outer spore-wall assembly.
ascospore wall	provides	spore environmental stress resistance	`DOI:10.1128/MMBR.69.4.565-584.2005` Neiman 2005 reviews the mature spore wall as a source of environmental stress resistance. `DOI:10.1371/journal.pone.0002873` Coluccio et al. 2008 showed that the yeast spore wall enables survival through the Drosophila digestive tract.

Discussions

INTERPRETATION (RESOLVED): Split Saccharomyces ascospore-wall layers into standalone records. GO has exact cellular-component terms for the Saccharomyces inner, chitosan, and dityrosine spore-wall layers; GO:1990916 separately denotes the Schizosaccharomyces pombe Isp3 layer.
CURATION_TODO (OPEN): Resolve exact source-neutral component groundings for the ascospore-wall polysaccharides and dityrosine-rich outer material. The remaining ungrounded mannan/glucan and dityrosine-rich material labels are reviewed but ungrounded until exact CHEBI or polymer identifiers can be confirmed; the chitosan polymer component is now grounded to CHEBI:16261.

Evidence

GO:0005619 Gene Ontology cellular-component term for ascospore wall.
GO:0009277 Gene Ontology cellular-component term for the broader fungal-type cell wall.
GO:0005632 Gene Ontology cellular-component term for inner layers of the Saccharomyces spore wall.
GO:0005631 Gene Ontology cellular-component term for the Saccharomyces spore-wall chitosan layer.
GO:0005630 Gene Ontology cellular-component term for the Saccharomyces spore-wall dityrosine layer.
GO:1990916 Gene Ontology cellular-component term for the Schizosaccharomyces pombe Isp3 spore-wall layer.
DOI:10.1128/MMBR.69.4.565-584.2005 Neiman 2005, Ascospore Formation in the Yeast Saccharomyces cerevisiae, Microbiology and Molecular Biology Reviews.
DOI:10.1128/EC.3.6.1464-1475.2004 Coluccio et al. 2004, Morphogenetic pathway of spore wall assembly in Saccharomyces cerevisiae, Eukaryotic Cell.
DOI:10.1371/journal.pgen.1003700 Lin et al. 2013, A Highly Redundant Gene Network Controls Assembly of the Outer Spore Wall in S. cerevisiae, PLOS Genetics.
DOI:10.1371/journal.pone.0002873 Coluccio et al. 2008, The Yeast Spore Wall Enables Spores to Survive Passage through the Digestive Tract of Drosophila, PLOS ONE.

Curation history

2026-09-22T08:12:08Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-22T08:14:23Z codex · EXPANDED_RECORD — Added fungal cell-wall parentage, Saccharomyces spore-wall layer parts, reviewed-label-only wall-polymer components, Saccharomyces scope, a stress-barrier function, a nonmechanistic layer topology graph, DOI/GO evidence, and layer/component grounding TODOs.
2026-09-23T01:10:09Z codex · UPDATED_PARENT_RELATION — Added GO:1990916 to ascospore wall has_part after creating a standalone Isp3 layer record and narrowed the open layer-splitting TODO to the remaining Saccharomyces spore-wall layers.
2026-09-23T01:20:29Z codex · ADDRESS_REVIEW — Resolved PR #1340 review issue #1341 by adding GO:1990916 record-level evidence to support the new ascospore wall has_part link to the Isp3 layer.
2026-09-23T01:41:48Z codex · UPDATED_CHILD_RECORD_BOUNDARY — Removed GO:0005630 from the open ascospore layer-splitting TODO after creating a standalone dityrosine layer record.
2026-09-23T02:13:19Z codex · UPDATED_CHILD_RECORD_BOUNDARY — Removed GO:0005631 from the open ascospore layer-splitting TODO after creating a standalone chitosan layer record and grounded the parent chitosan polymer component to CHEBI:16261.
2026-09-23T02:22:03Z codex · NORMALIZED_COMPONENT_LABEL — Renamed the parent ascospore-wall chitosan component to the CHEBI:16261 canonical label after grounding it to chitosan during standalone GO:0005631 curation.
2026-09-23T02:32:50Z codex · ADDRESS_REVIEW — Resolved PR #1344 review issue #1346 by adding an explicit GO:0005631 structure node to the ascospore wall layer graph and rewiring topology edges to the chitosan layer rather than the CHEBI-grounded polymer node.
2026-09-23T02:56:26Z codex · UPDATED_CHILD_RECORD_BOUNDARY — Resolved the ascospore layer-splitting TODO after creating a standalone GO:0005632 inner layer record and rewired parent topology edges to an explicit inner spore-wall layer structure node.
2026-09-23T03:10:48Z codex · ADDRESS_REVIEW — Resolved PR #1347 review issue #1348 by adding GO:0005632 and Neiman 2005 support to the parent polymer-grounding TODO that tracks the unresolved inner-wall mannan/beta-glucan component.

Source: data/structures/spore/ascospore_wall.yaml