Protein PHOSPHATE STARVATION RESPONSE 2; Transcription factor involved in phosphate starvation signaling. Binds to P1BS, an imperfect palindromic sequence 5'-GNATATNC-3', to promote the expression of inorganic phosphate (Pi) starvation-responsive genes. Functionally redundant with PHR1 and PHR3 in regulating Pi starvation response and Pi homeostasis. Involved in both systematic and local Pi-signaling pathways. Regulates several Pi transporters. Regulates the expression of PT2. Directly up-regulates SPX1 and SPX2 expression, but PHR2 binding to DNA is repressed redundantly by SPX1 and S [...]

SPX domain-containing protein 1; Involved in plant adaptation to phosphate starvation. Inhibits PHR2 DNA-binding activity via a Pi- dependent protein interaction. Suppresses the regulation on expression of PT2 by PHR2 and accumulation of shoot Pi. Optimizes growth under phosphate-limited conditions through a negative feedback loop of the PSI (phosphate starvation- induced) signaling pathway. Regulates the expression of SPX2, SPX3 and SPX5. May be an important link between signal transduction pathways related to phosphate starvation and cold stress.

Putrescine hydroxycinnamoyltransferase 1; Hydroxycinnamoyl transferase that catalyzes the transfer of an acyl from p-coumaryol-CoA to putrescine, to produce coumaroyl putrescine; Belongs to the plant acyltransferase family.

SPX domain-containing protein 2; Inhibits PHR2 DNA-binding activity via a Pi-dependent protein interaction.

SPX domain-containing protein 4; Inositol polyphosphate sensor that associates with transcription factors to regulate Pi starvation responses. The SPX domain provides a basic binding surface for inositol polyphosphate signaling molecules. Interacts with PHR2 to inhibits its translocation to the nucleus and repress its DNA-binding activity, and then negatively regulate Pi signaling.

SPX domain-containing protein 3; Functional repressor of PHR2. Involved in maintaining cellular Pi homeostasis when plants are exposed to an external change in Pi. Negatively regulates root-to- shoot Pi translocation redundantly with SPX3. Downregulates the non-coding RNA IPS1 (At3g09922) and suppresses the responses of miR399 and PHO2 to Pi-starvation.

Phosphate transporter PHO1-2; Involved in the transfer of inorganic phosphate (Pi) from roots to shoots.

SPX domain-containing protein 5; Functional repressor of PHR2. Involved in maintaining cellular Pi homeostasis when plants are exposed to an external change in Pi. Negatively regulates root-to- shoot Pi translocation redundantly with SPX3.

SPX domain-containing protein 6; May be involved in maintaining cellular Pi homeostasis when plants are exposed to an external change in Pi.