bipolar mating system

traitmech:000616 · CLASS · PROPOSED

A fungal mating phenotype in which compatibility between partners is governed by a single segregating mating-type factor.

Trait evidence (2)

DOI:10.1073/pnas.91.15.7085
A bipolar system is defined by a single genetic locus (MAT) that can have two or multiple alleles.

Bakkeren and Kronstad (1994), PMID:7913746, PMC44343. Exact scientific-abstract sentence directly retrieved from Europe PMC core metadata. The abstract reports cloning of Ustilago hordei a1 and physical linkage of a and b into a complex MAT region, contrasted with genetically unlinked loci in U. maydis. The compatibility factor is not necessarily one gene. This supports definition and a reported linkage architecture, not a fresh verification of native crossing assays. Full text, figures, methods, supplements and natural strain provenance remain uninspected; no canonical strain is inferred.
DOI:10.1534/genetics.105.051128
All of the 24 collections displayed a bipolar mating system with only two mating types among all progeny of a collection.

James et al. (2006), PMID:16461425, PMC1456265. Exact sentence in the first Results subsection on p. 1881, visually checked in the published PDF at https://public.websites.umich.edu/~mycology/resources/Publications/james2006.genetics.pdf; not an abstract quote. Native Coprinellus disseminatus single-spore crosses support the compatibility phenotype. Two types per collection does not mean only two across the species. Methods score clamps and dikaryotization, not automatically completed fertile sex; poor-mating progeny were excluded when choosing population testers. Table 3 shows segregation in 13 TJ00/38 progeny: MIP tracks mating type, whereas CDSTE3.1-.3 do not. Its plus/minus states are PCR-RFLP genotypes, not gene presence or absence; CDSTE3.4 lacks segregation data. The abstract reports heterologous sexual responses, not loss of all pheromone-receptor function. PDF pp. 1877-1882 and actual Tables 1-3 were read; pp. 1883-1884 were text-extracted only. Actual figures, later Results/Discussion and supplements remain uninspected. Natural North Carolina fruit-body provenance is described in Methods, but active taxon authority and the intersterile Japanese group remain unresolved; no canonical taxon assertion is made.

Provenance

Identifier source: TraitMech local identifier
Definition source: DOI:10.1073/pnas.91.15.7085

Parent traits (1)

phenotype METPO:1000059

kg-microbe context

No kg-microbe node embedding matched this record in the 2026-04-25 deepwalk.

Discussions and Knowledge Gaps (2)

Open questions attached to this trait. Seeded by just knowledge-gap-scan and curated; see the corpus-wide index.

Keep genetic compatibility distinct from locus inventory and partner dependence.

CURATION TODO OPEN bipolar-mating-scope-and-hierarchy · raised by codex · 2026-10-05

Not yet attached to a section of this record — a curator sets attaches_to (e.g. causal_graphs#some_edge) so the gap shows beside the mechanism it concerns.

A single segregating compatibility factor need not be one gene, exactly two specificities across a species, or fused pheromone/receptor and homeodomain loci. Bakkeren describes recognition in heterothallic basidiomycetes, but its examples do not establish universal separate-partner dependence under the organism-level definition of traitmech:000610. The functional compatibility axis differs from self-fertility and from tetrapolar mating (traitmech:000615), which requires differences at two independently segregating factors. Use released phenotype METPO:1000059 in record and proposal; do not assert disjointness with homothallism, universal self-sterility or a sufficient guarantee of fertility. Resolve unifactorial terminology and external equivalences before adding synonyms or xrefs. PHYSIOLOGY is a filesystem category, not a narrower ontology parent.

Resolve native mechanisms and taxon authority before adding graphs or examples.

CURATION TODO OPEN bipolar-mating-mechanism-and-examples · raised by codex · 2026-10-05

Not yet attached to a section of this record — a curator sets attaches_to (e.g. causal_graphs#some_edge) so the gap shows beside the mechanism it concerns.

Complete unread source sections and inspect actual figures and supplements before extending mechanistic claims. Loss of mating-type specificity is not absence of receptor genes or loss of every cellular function. Keep native compatibility assays, genetic segregation, heterologous responses and completed fertile reproduction distinct. Resolve NCBI taxon authority and strain scope before canonical examples, and native protein accessions plus tested dependencies before causal edges. No NONMECHANISTIC graph bypasses grounding. Manual full-text checks do not replace the abstract resolver's actual verdict.

Curation history

2026-10-05T08:34:00Z · MINTED_TRAITMECH_ID · codex
Added bipolar mating system with two primary DOI-backed sources and verbatim snippets. Kept single-factor compatibility distinct from gene inventory, globally two mating types, one molecular architecture and partner dependence. Ignored-and-hidden novelty and allocation searches found no exact record or ID collision. Reserved METPO:1057000 in v493 under released phenotype. Deferred canonical taxon assertions, lexical mappings, native protein graphs and explicitly unread source material.
2026-10-05T08:39:00Z · CORRECTED_EVIDENCE_LOCATOR · codex
Corrected the James p. 1881 locator: the verbatim quote is in the first Results subsection, not its first sentence (#1706). The quotation and biological interpretation are unchanged.