identifier: traitmech:000324 label: RexAB system definition: An abortive infection system in which an organism possesses a bacteriophage-lambda Rex-family locus represented by the DefenseFinder RexAB__RexA and RexAB__RexB profiles and exemplified by the rexA and rexB two-component system that aborts lytic growth of bacterial viruses. definition_source: DOI:10.1101/gad.6.3.497 trait_category: GENOMICS term_kind: CLASS mapping_status: PROPOSED parent_traits: - traitmech:000214 synonyms: - synonym_text: RexAB synonym_type: RELATED_SYNONYM source: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md evidence: - reference: DOI:10.1101/gad.6.3.497 snippet: The rexA and rexB genes of bacteriophage lambda encode a two-component system that aborts lytic growth of bacterial viruses. notes: Parma et al. support RexA and RexB as a two-component Rex exclusion system. - reference: DOI:10.1101/gad.6.3.497 snippet: Rex exclusion is characterized by termination of macromolecular synthesis, loss of active transport, the hydrolysis of ATP, and cell death. notes: Parma et al. support Rex exclusion as an abortive-infection-like output with host-cell death. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: 'RexAB | 10\.1101/gad\.6\.3\.497 | The Rex system of bacteriophage lambda: tolerance and altruistic cell death' notes: The DefenseFinder article registry maps the named RexAB model namespace to the bacteriophage-lambda Rex system paper. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv snippet: "RexAB\tRexAB\t2\t2\tRexAB__RexA, RexAB__RexB" notes: The DefenseFinder rules table models RexAB as a two-component system requiring the RexA and RexB profiles. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md snippet: '| RexAB__RexA | RexAB__RexA | RexAB | PF15969.7 | 25 |' notes: The DefenseFinder HMM inventory records RexAB__RexA under RexAB. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md snippet: '| RexAB__RexB | RexAB__RexB | RexAB | PF15968.7 | 27 |' notes: The DefenseFinder HMM inventory records RexAB__RexB under RexAB. causal_graphs: - graph_id: rexab_locus_mediates_rex_exclusion title: RexAB loci mediate abortive Rex exclusion description: Conservative system-level sketch linking RexA/RexB locus possession to Rex exclusion and RexAB-system possession without asserting the direct phage trigger, RexA/RexB stoichiometry, membrane target, or bacteriophage-lambda self-protection route. scope_status: NONMECHANISTIC scope_notes: The graph captures RexAB as a named DefenseFinder two-profile abortive-infection system whose lambda prototype aborts lytic growth. It leaves the direct phage trigger, RexA/RexB molecular coupling, ion-channel activity, self-exclusion control, and phage escape routes unresolved. nodes: - node_id: rexab_locus label: RexAB locus node_type: GENETIC_ELEMENT description: A bacteriophage-lambda Rex-family abortive exclusion locus represented by the DefenseFinder RexAB__RexA and RexAB__RexB profiles. - node_id: rex_exclusion label: Rex exclusion node_type: BIOLOGICAL_PROCESS description: Abortive exclusion of sensitive bacteriophages in cells carrying RexA and RexB. - node_id: rexab_system_trait label: RexAB system node_type: TRAIT grounding: traitmech:000324 description: Possession of a genome-encoded RexAB abortive-infection phage-defense system. edges: - subject: rexab_locus predicate: contributes to predicate_id: RO:0002326 object: rex_exclusion description: The bacteriophage-lambda RexA/RexB system aborts lytic growth of bacterial viruses, and DefenseFinder represents RexAB with required RexA and RexB profiles. evidence: - reference: DOI:10.1101/gad.6.3.497 snippet: The rexA and rexB genes of bacteriophage lambda encode a two-component system that aborts lytic growth of bacterial viruses. notes: Parma et al. support RexA and RexB as the core genetic components of Rex exclusion. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/DefenseFinder_rules.tsv snippet: "RexAB\tRexAB\t2\t2\tRexAB__RexA, RexAB__RexB" notes: The DefenseFinder rules table models RexAB as a two-component system requiring the RexA and RexB profiles. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md snippet: '| RexAB__RexA | RexAB__RexA | RexAB | PF15969.7 | 25 |' notes: The DefenseFinder HMM inventory records RexAB__RexA under RexAB. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/Liste_hmm_system.md snippet: '| RexAB__RexB | RexAB__RexB | RexAB | PF15968.7 | 27 |' notes: The DefenseFinder HMM inventory records RexAB__RexB under RexAB. - subject: rex_exclusion predicate: confers predicate_id: METPO:2007700 object: rexab_system_trait description: RexA/RexB-dependent abortive exclusion realizes the RexAB system trait. evidence: - reference: DOI:10.1101/gad.6.3.497 snippet: Rex exclusion is characterized by termination of macromolecular synthesis, loss of active transport, the hydrolysis of ATP, and cell death. notes: Parma et al. connect Rex exclusion to host-cell shutdown and death. - reference: https://raw.githubusercontent.com/mdmparis/defense-finder-models/afb0e5a8b466be53586b13266f5d38d98c3ac268/List_system_article.md snippet: 'RexAB | 10\.1101/gad\.6\.3\.497 | The Rex system of bacteriophage lambda: tolerance and altruistic cell death' notes: The DefenseFinder article registry maps the named RexAB model namespace to the bacteriophage-lambda Rex system paper. discussions: - discussion_id: rexab-mechanism-gap prompt: Resolve the direct RexAB phage trigger, RexA and RexB molecular coupling, ion-channel activity, lambda self-exclusion control, and sensitive-phage escape routes before minting narrower RexAB mechanism children. kind: KNOWLEDGE_GAP status: OPEN rationale: Parma et al. support bacteriophage-lambda rexA and rexB as a two-component system that aborts lytic growth of bacterial viruses, and DefenseFinder maps RexAB to RexAB__RexA and RexAB__RexB profiles. The direct phage trigger, RexA/RexB molecular coupling, ion-channel output, lambda self-exclusion control, and sensitive-phage escape routes remain unresolved. attaches_to: - causal_graphs#rexab_locus_mediates_rex_exclusion posed_by: codex posed_date: '2026-09-21' curation_history: - timestamp: '2026-09-21T02:17:07Z' curator: codex action: MINTED_TRAITMECH_ID changes: Minted RexAB system as a DOI-backed GENOMICS TraitRecord under the abortive infection system parent after an ignored-and-hidden duplicate review found no exact live TraitMech, METPO, history, or prior proposal record; the replacement placeholder is reserved in proposals/metpo_traitmech_v201. llm_assisted: true - timestamp: '2026-09-21T02:17:08Z' curator: codex action: REVIEW_CANONICAL_EXAMPLE_EVIDENCE_GAP changes: 'Reviewed canonical example evidence while minting RexAB system and left canonical_examples empty: the bacteriophage-lambda prototype supports a prophage-encoded rexA and rexB exclusion system and the pinned DefenseFinder registry maps a two-profile RexAB namespace, but the available curation sources do not identify a natural organism instance with a directly observed RexAB locus. No paid research was used.' llm_assisted: true