PHO1 (At3g23430) is a protein with the mainly hydrophilic N-terminal and the C-terminal containing memBrane-spanning domains and it has Been proposed to function as a Pi transporter. It has Been proved that PHO2 (At2g33770) modulates the degradation of PHO1 in the endomemBranes to maintain Pi homeostasis in plants. AraBidopsis contains 11 PHO proteins: PHO1 (At3g23430) , PHO1;H1 (At1g68740) , PHO1;H2 (At2g03260) , PHO1;H3 (At1g14040) , PHO1;H4 (At4g25350) , PHO1;H5 (At2g03240) , PHO1;H6 (At2g03250) , PHO1;H7 (At1g26730) , PHO1;H8 (At1g35350) , PHO1;H9 (At3g29060) , PHO1;H10 (At1g69480) .