2.A.94 The Phosphate Permease (Pho1) Family

Pho1 of A. thaliana is a member of the PHO1 family (11 paralogues in A. thaliana). It functions in inorganic phosphate transport and homeostasis. Pho1 catalyzes efflux of phosphate from epidermal and cortical cells into the xylem (Quaghebeur and Rengel, 2004; Stefanovic et al., 2007). The SPX superfamily domain is an N-terminal soluble domain. These proteins belong to the EXS (Erd1/Xpr1/Syg1) superfamily. 

The generalized reaction catalyzed by Pho1 is:

Pi (cells) → Pi (xylem)

This family belongs to the IT Superfamily.

This family belongs to the IT Superfamily.



Hamburger, D., E. Rezzonico, J. MacDonald-Comber Petétot, C. Somerville, and Y. Poirier. (2002). Identification and characterization of the Arabidopsis PHO1 gene involved in phosphate loading to the xylem. Plant Cell 14: 889-902.

Quaghebeur, M., and Z. Rengel. (2004). Arsenic uptake, translocation and speciation in pho1 and pho2 mutants of Arabidopsis thaliana. Physiol. Plant. 120: 280-286.

Stefanovic, A., C. Ribot, H. Rouached, Y. Wang, J. Chong, L. Belbahri, S. Delessert, and Y. Poirier. (2007). Members of the PHO1 gene family show limited functional redundancy in phosphate transfer to the shoot, and are regulated by phosphate deficiency via distinct pathways. Plant J. 50: 982-994.


TC#NameOrganismal TypeExample

Putative phosphate transporter, Pho1 (one of ten paralogues) (782 aas; 7 - 12 TMSs) (Hamburger et al., 2002)


Pho1 of Arabidopsis thaliana (Q8S403)


Xenotropic and polytropic murine-leukemia virus receptor Xpr1 of 671 aas and 11 or 12 TMSs.


Xpr1 of Culex pipiens (XP_001850310)


Pho1 homologue of 396 aas and probably either 10 or 12 TMSs, ERD1.

ERD1 of Cercospora beticola


EXS-domain-containing protein of 565 aas and probably 10 TMSs.

EXS protein of Mortierella elongata


EXS family protein of 414 aas and ~ 8 TMSs.

EXS protein of Tetrahymena thermophila