mating projection septin ring

GO:0032175 · Cytoskeleton · Filament · Proposed

A septin ring, i.e. a ring-shaped structure composed of septins and septin-associated proteins, located at the neck of a shmoo (mating projection). The septin ring in the neck of a shmoo may act as a barrier to localize mating factors in the shmoo tip. [GO:0032175]

Part of: mating projection (GO:0005937)

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
septin proteins	Protein	part of	Reviewed label only (reviewed name; no accession asserted)			UNKNOWN	Septin GTPases that assemble into the ring-shaped structure at the neck of the mating projection. `GO:0032175` GO:0032175 defines the mating projection septin ring as composed of septins and septin-associated proteins. `DOI:10.1091/mbc.8.6.987` Giot and Konopka 1997 linked the Cdc12p septin with Afr1p during pheromone-induced Saccharomyces morphogenesis, supporting the open shmoo-neck accessory-boundary question.

Functions

shmoo-neck mating-factor barrier — The mating projection septin ring can act at the shmoo neck as a barrier that helps retain mating factors in the projection tip.
- GO:0032175 GO:0032175 defines the shmoo-neck septin ring and its barrier role in localizing mating factors to the shmoo tip.
- DOI:10.1128/EC.4.9.1503-1512.2005 Douglas et al. 2005 reviewed septin functions in yeast model systems and pathogenic fungi.

Mechanism graphs

Shmoo-neck septin ring topology (FUNCTION)

The mating projection septin ring is a localized septin ring that assembles at the neck of the pheromone-induced mating projection.

Subject	Predicate	Object	Evidence
mating projection septin ring	is a	septin ring	`GO:0032175` GO:0032175 identifies a mating-projection-localized septin ring. `GO:0005940` GO:0005940 identifies the broader septin ring.
mating projection septin ring	is part of	mating projection	`GO:0032175` GO:0032175 places the septin ring at the neck of a mating projection.
septin proteins	assemble into	mating projection septin ring	`GO:0032175` GO:0032175 defines the structure as a ring composed of septins and septin-associated proteins.

Discussions

CURATION_TODO (OPEN): Resolve which Afr1 and additional shmoo-neck-associated proteins should be curated as mating-projection septin-ring constituents, and separate ring-shaped GO:0032175 examples from diffuse septin-band GO:0032162 examples. GO:0032175 includes septin-associated proteins in the ring definition, and Giot and Konopka 1997 connected Afr1p with Cdc12p in pheromone-induced morphogenesis. Douglas et al. 2005 distinguish S. cerevisiae shmoo-neck septins from tight mitotic rings as a diffuse ring or series of bars, so this record deliberately avoids using S. cerevisiae as a ring-specific canonical example until the GO:0032175 ring versus GO:0032162 band boundary is resolved from primary evidence.

Evidence

GO:0032175 Gene Ontology cellular-component term for the mating projection septin ring.
GO:0005940 Gene Ontology cellular-component parent for the septin ring.
GO:0005937 Gene Ontology cellular-component term for the mating projection.
DOI:10.1091/mbc.8.6.987 Giot and Konopka 1997, 'Functional analysis of the interaction between Afr1p and the Cdc12p septin, two proteins involved in pheromone-induced morphogenesis', Molecular Biology of the Cell.
DOI:10.1128/EC.4.9.1503-1512.2005 Douglas et al. 2005, 'Septin function in yeast model systems and pathogenic fungi', Eukaryotic Cell.

Curation history

2026-09-28T15:48:55Z codex · CREATED_RECORD — Scaffolded by scripts/new_record.py
2026-09-28T15:50:12Z codex · EXPANDED_RECORD — Added septin-ring parentage, mating-projection parthood, a label-only septin constituent, Saccharomyces distribution and example evidence, a shmoo-neck barrier function, GO and DOI evidence, a nonmechanistic shmoo-neck septin-ring topology graph, and a septin-accessory boundary TODO.
2026-09-28T16:32:20Z codex · ADDRESSED_REVIEW — Resolved #1732 by removing the over-specific S. cerevisiae distribution and canonical example, narrowing Giot and Konopka evidence to Cdc12/Afr1 boundary context, and documenting the GO:0032175 ring versus GO:0032162 band distinction.

Source: data/structures/cytoskeleton/mating_projection_septin_ring.yaml