---
layout: rule
id: GORULE:0000015
title: "Dual species taxon check"
type: report
fail_mode: soft
status: implemented
contact: "go-quality@lists.stanford.edu"
examples:
  fail:
    - comment: fails because GO:0005886 plasma membrane is not a child of "GO:0018995 host cellular component"
      format: gaf
      input: "UniProtKB	O56786	hol187		GO:0005886	PMID:10419939	IDA		C	Holin protein Hol187	hol187	protein	taxon:55511|taxon:9696	20170423	CACAO"
    - comment: fails because "neutrophil chemotaxis" is not a child of "GO:0044419 interspecies interaction between organisms"
      format: gaf
      input: "UniProtKB	A0A0K2S4Q6	CD300H		GO:0030593	PMID:26221034	IDA		P	Protein CD300H	CD300H	protein	taxon:9606|taxon:55511	20160428	UniProt"
  pass:
    - comment: Should pass because "defense response to Gram-positive bacterium" is a child of "GO:0044419 interspecies interaction between organisms"
      format: gaf
      input: "UniProtKB	A0A0B5JW41	cd59		GO:0050830	PMID:23707788	IDA		P	UPAR/Ly6 domain-containing protein	cd59	protein	taxon:7955|taxon:90370	20130923	ZFIN"
    - comment: Should pass because "host cell plasma membrane" is a child of "GO:0018995 host cellular component"
      format: gaf
      input: "UniProtKB	O56786	hol187		GO:0020002	PMID:10419939	IDA		C	Holin protein Hol187	hol187	protein	taxon:55511|taxon:9696	20170423	CACAO"
---
For background: dual (or multiple) species annotations are used to capture information about multi-species interactions. The first taxon ID should be that of the species encoding the gene product annotated, and the second (and further) IDs should be the taxon of the other species in the interaction. 

* Each value in the Taxon column (GAF column 13) should be unique. 

This rule applies to annotations to either these terms of their is_a descendants: 
* GO:0044419 biological process involved in interspecies interaction between organisms
* GO:0043903 regulation of biological process involved in symbiotic interaction, or
* GO:0018995 host cellular component

* Annotations to other terms should have a single value in the Taxon column (GAF column 13).