ApiLoc - A database of published protein sub-cellular localisation in Apicomplexa

version 3 (curated until May 28, 2011)

A cluster of four surface antigen genes specifically expressed in bradyzoites, SAG2CDXY, plays an important role in Toxoplasma gondii persistence.

Saeij, J. P., Arrizabalaga, G., Boothroyd, J. C. (2008 Jun, Infect Immun)

Toxoplasma gondii is one of the most successful protozoan parasites of warm-blooded animals. Stage-specific expression of its surface molecules is thought to be key to its ability to establish chronic infection in immunocompetent animals. The rapidly dividing tachyzoite stage displays a different subset of family of surface antigen 1 (SAG1)-related sequences (SRSs) from that displayed by the encysted bradyzoite stage. It is possible that this switch is necessary to protect the bradyzoites against an immune response raised against the tachyzoite stage. Alternatively, it might be that bradyzoite SRSs evolved to facilitate invasion of different cell types, such as those found in the brain, where cysts develop, or the small intestine, where bradyzoites must enter after oral infection. Here we studied the function of a cluster of four tandem genes, encoding bradyzoite SRSs called SAG2C, -D, -X, and -Y. Using bioluminescence imaging of mice infected with parasites expressing firefly luciferase (FLUC) driven by the SAG2D promoter, we show stage conversion for the first time in living animals. A truncated version of the SAG2D promoter (SAG2Dmin) gave efficient expression of FLUC in both tachyzoites and bradyzoites, indicating that the bradyzoite specificity of the complete SAG2D promoter is likely due to an element(s) that normally suppresses expression in tachyzoites. Comparing mice infected with the wild type or a mutant where the SAG2CDXY cluster of genes has been deleted (DeltaSAG2CDXY), we demonstrate that whereas DeltaSAG2CDXY parasites are less capable of maintaining a chronic infection in the brain, they do not show a defect in oral infectivity.

PubMed: 18347037, full text

Localisation information

TGME49_007130 (SAG2Y) SRS49A (= SAG2Y)

Experimental localisation: parasite plasma membrane during bradyzoite, not tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: "Parasites were switched to bradyzoites by use of pH 8.1 switch medium for 4 days. Coverslips were fixed, permeabilized, and stained with a polyclonal rabbit antibody against SAG2Y (red), with Dolichos agglutinin-FITC (green) reacting with the cyst wall, and with the nuclear stain Hoechst (blue)."
  • Microscopy type: Light
  • Microscopy method: polyclonal antibody directly to protein
  • Strain: Pru
  • Gene model mapping comments: Taken directly from 18347037
  • Localisation record: surface during bradyzoite, not during tachyzoite

TGME49_108020 (SAG3, P43) SRS57 (= SAG3, P43)

Experimental localisation: host cell plasma membrane during tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: ""
  • Microscopy type:
  • Microscopy method:
  • Strain:
  • Gene model mapping comments: inferred from another publication
  • Localisation record: host cell plasma membrane during tachyzoite

TGME49_033450 (SRS1) SRS29A (= SRS1)

Experimental localisation: host cell plasma membrane during tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: ""
  • Microscopy type:
  • Microscopy method:
  • Strain:
  • Gene model mapping comments: inferred from another publication
  • Localisation record: host cell plasma membrane during tachyzoite

TGME49_033480 (SRS2) SRS29C (= SRS2, P35)

Experimental localisation: host cell plasma membrane during tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: ""
  • Microscopy type:
  • Microscopy method:
  • Strain:
  • Gene model mapping comments: inferred from another publication
  • Localisation record: host cell plasma membrane during tachyzoite

TGME49_108840 (SRS3) SRS51 (= SRS3)

Experimental localisation: host cell plasma membrane during tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: ""
  • Microscopy type:
  • Microscopy method:
  • Strain:
  • Gene model mapping comments: inferred from another publication
  • Localisation record: host cell plasma membrane during tachyzoite

TGME49_007160 (SAG2C) SRS49D (= SAG2C)

Experimental localisation: host cell plasma membrane during bradyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: ""
  • Microscopy type:
  • Microscopy method:
  • Strain:
  • Gene model mapping comments: inferred from another publication
  • Localisation record: host cell plasma membrane during bradyzoite

TGME49_112270 (ROP13) hypothetical protein

Experimental localisation: rhoptry body during tachyzoite
  • Species: Toxoplasma gondii
  • Quote inferring localisation: ""
  • Microscopy type:
  • Microscopy method:
  • Strain:
  • Gene model mapping comments: inferred from another publication
  • Localisation record: rhoptry body during tachyzoite