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microbial haustorium formation

traitmech:000663 · CLASS · PROPOSED

A morphological phenotype in which a fungus or oomycete forms specialized hyphal outgrowths, called haustoria, that establish intimate interfaces with living host cells.

Trait evidence (4)

  • DOI:10.1016/j.fgb.2014.08.006
    The haustorium is separated from the extrahaustorial membrane (em) by the extrahaustorial matrix (emx).

    Martinez-Cruz et al. (2014), PMID:25151531; primary PDF at https://powderymildew.ucr.edu/wp-content/uploads/2017/04/MPM14.pdf. Abstract, Introduction, Methods and main text were read; actual Figures 2-4 and complete pages 24-26 were visually inspected. The quote is from Figure 3's caption. Podosphaera xanthii isolate 2086 forms haustoria within melon epidermal cells. This supports the fungal formation phenotype and this interface anatomy, not a universal membrane arrangement. Callose correlates with maturity; functional partitioning of lobes and putative exosomes remains an interpretation. Remaining actual figures and supplements were not inspected. Initial natural-isolation provenance for 2086 was not established, so it is not used as a canonical example.

  • DOI:10.1080/00275514.1994.12026373
    A single micropore connected the cytoplasm of the haustorial filament with that of the host cell.

    Zugmaier, Bauer and Oberwinkler (1994), Mycologia 86:49-56; all eight pages and actual Figures 1-16 directly inspected at https://dr-franz.oberwinkler.de/wp-content/uploads/Tremella_mycoparasitism.pdf. The snippet is from the scientific abstract on page 49, visually checked because OCR is poor. Crossref confirms this DOI, title, authors and 1994 print date; its 2018 online date is not the study year. Field and culture observations distinguish tremelloid haustorial cells, filaments and host-dependent micropores. Membrane continuity was visible only under optimal sectioning; some captions say probably or presumed. Some tested hosts had attached filaments without an observed continuous micropore. Static microscopy is not a nutrient-flux assay, and formation does not guarantee a successful feeding connection.

  • DOI:10.1111/mpp.13072
    We transformed P. kernoviae to express green fluorescent protein (GFP) and demonstrated that it forms haustoria within infected N. benthamiana cells.

    Wang et al. (2021), PMID:34018655, PMC8295517; scientific abstract, Results 2.1, Figure 1 caption and Methods 4.1, 4.6 and 4.7 read in directly retrieved full-text XML. The quoted abstract sentence explicitly identifies transformation. Imaging used engineered GFP line PkGFP8 derived from SCRP1055 and transgenic Nicotiana benthamiana membrane markers. Results call the projections likely biotrophic haustoria; the caption says they appeared in natural hosts without membrane markers. Those hosts are not unmodified-pathogen controls. Actual figures, supplements and complete remaining Methods were not inspected. This supports oomycete scope with engineering qualifiers, not a natural canonical example or a requirement for lifelong obligate biotrophy.

  • DOI:10.1104/pp.18.00979
    Biotrophic and hemibiotrophic oomycetes form intimate associations with their hosts using haustoria

    Judelson and Ah-Fong (2019), PMID:30538168, PMC6446794; publisher HTML at https://academic.oup.com/plphys/article/179/4/1198/6116504 read directly after PMC and Europe PMC access failed. The clause precedes a figure citation in HAUSTORIA REPRESENT A SPECIALIZED INTERFACE. This is a review, not another formation experiment. Its interface and nutrient-acquisition passages distinguish demonstrated effector secretion from then-unproven nutritional importance in oomycetes. Neither a universal transport mechanism nor a present-day absence of such evidence is inferred. Actual figures and cited underlying experiments were not inspected.

Provenance

Identifier source
TraitMech local identifier
Definition source
DOI:10.1016/j.fgb.2014.08.006

Parent traits (1)

kg-microbe context

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

Canonical examples (1)

Organisms cited as exemplars of this trait. Taxon ids are NCBITaxon and link out to the NCBI record.

  • Tremella mesenterica NCBITaxon:5217 DOI:10.1080/00275514.1994.12026373 Field-collected material in Zugmaier et al. (1994), Methods page 51, field Results page 53 and Figures 1-9. Collections from Haldenwald near Sonnenberg, Stuttgart, Germany, on Carpinus betulus adjacent to Peniophora laeta include 8 June 1987 and 20 November 1989, W. Zugmaier 97 and 158. The authors observed tremelloid haustorial cells and filaments in contact with P. laeta and micropore connections. Figures are not assigned individually to one voucher; no such match is invented. Their separate laboratory culture was obtained by crossing monospore cultures from different basidiomata and is not equated to an unmodified field isolate. NCBI Taxonomy confirms ID 5217, label and species rank; the field material is not identified as NCBI type strain CBS 6973. The directly inspected primary PDF is https://dr-franz.oberwinkler.de/wp-content/uploads/Tremella_mycoparasitism.pdf.

Discussions and Knowledge Gaps (2)

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

Resolve a closer parent and the haustorium/arbuscule boundary.

CURATION TODO OPEN microbial-haustorium-scope-and-hierarchy · raised by codex · 2026-10-07

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.

Use phenotype METPO:1000059. Fungal appressorium formation traitmech:000659 concerns surface-associated penetration structures, not this intimate host-cell interface. Plant pathogen METPO:1004003 is not a required parent because fungal hosts are supported. Mycorrhization METPO:1000198 is obsolete. Direct QuickGO authority checks resolve GO:0085035 haustorium as a cellular component and GO:0052094 formation of haustorium for nutrient acquisition as a biological process, not exact organism-level phenotypes. GO:0085041 arbuscule is an is_a child of GO:0085035, whereas literature often distinguishes arbuscules from parasitic haustoria. Preserve that attributed umbrella usage: the definition is not restricted to pathogenicity, but arbuscule formation is not asserted as an exact synonym or given a new hierarchy here. The GO membrane-invagination definition does not describe every tremelloid micropore interface. No xrefs or SSSOM equivalences are asserted. Parasitic-plant haustorial organs are outside this microbial hyphal scope; fungi and oomycetes are both included. Fungal arbuscule formation now has its own source-bounded phenotype record, traitmech:000664. This resolves the missing record reference, not the umbrella hierarchy question; no subclass or disjointness relationship between these two phenotypes is asserted.

Separate observed formation from feeding and formation mechanisms.

KNOWLEDGE GAP OPEN microbial-haustorium-formation-and-function · raised by codex · 2026-10-07

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.

Haustorium formation alone does not demonstrate nutrient flux, effector delivery, pathogenicity, a universal shape or a shared membrane topology. Keep tremelloid cytoplasmic connections distinct from plant-pathogen extrahaustorial compartments. Attached filaments without an observed micropore are not proven successful feeding sites. Oomycete transformed imaging and source-specific likely/appeared language must remain visible; natural host means the host species, not an unmodified pathogen. Formation regulation requires direct perturbation evidence and authority-verified protein examples. The protein-resolved causal graph is deferred, not claimed to be biologically absent.

Curation history

  1. · MINTED_TRAITMECH_ID · codex

    Added microbial haustorium formation with four source-backed snippets, a field-qualified Tremella example and explicit interface, engineering and ontology limits. Ignored-and-hidden novelty checks found no exact record. Reserved METPO:1061600 in v539, avoiding pending v538. Existing traits unchanged; protein-level formation graph deferred.

  2. · LINK_ARBUSCULE_DISCUSSION · codex

    Linked the existing arbuscule boundary discussion to traitmech:000664; retained OPEN status and deferred subclass, equivalence and disjointness. No haustorium identity, evidence, examples or parent changed.

Recorded curation sessions

  • · codex
    • CREATE — Add source-qualified microbial haustorium formation

      Added traitmech:000663 with four directly inspected DOI-backed source spans, a field-observed Tremella mesenterica example, and explicit fungal/oomycete, membrane, engineering, ontology and functional limits. Reserved METPO:1061600 in v539 while pending PR 1783 holds traitmech:000662 and v538. Existing traits are unchanged. The guarded writer dry run and 20 focused tests passed before application; full corpus, proposal, taxonomy, snippet, rendered artifact and PR checks remain pending at this event. No independent review or merge is claimed.

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  • · codex
    • EDIT — Link arbuscule phenotype in the haustorium boundary discussion

      Appended traitmech:000664 as the explicit arbuscule formation reference without closing the hierarchy question or asserting subclass, equivalence or disjointness. Identity, parents, evidence and examples are unchanged. Full semantic preimage guarded; mutation uses write_validated_trait and record_curation_event. Writer dry run and 27 focused tests passed; broad validation remains pending.

    Read this curation session