Control of plant phosphate homeostasis by inositol pyrophosphates and the SPX domain

Curr Opin Biotechnol. 2018 Feb;49:156-162. doi: 10.1016/j.copbio.2017.08.012. Epub 2017 Sep 8.


Proteins containing a SPX domain are involved in phosphate (Pi) homeostasis, including Pi transport and adaptation to Pi deficiency. The SPX domain harbors a basic surface binding Pi at low affinity and inositol pyrophosphates (PP-InsPs) at high affinity. Genetic and biochemical studies revealed that PP-InsPs serve as ligands for the SPX domain. Residues in the PHO1 SPX domain involved in PP-InsPs binding are critical for its Pi export activity, and the interaction between SPX proteins and the PHR1 transcription factor, which results in PHR1 inactivation, is promoted by PP-InsPs. Changes in PP-InsPs levels in response to Pi deficiency may thus contribute to the adaptation of plants to stress via the modulation of the activity of SPX-containing proteins and their interactors. Modulating PP-InsP levels or the affinity/specificity of the SPX domain for PP-InsP could potentially be used to engineer crops to maintain high yield under reduced Pi fertilizer input.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Biological Transport
  • Homeostasis
  • Inositol Phosphates / metabolism*
  • Phosphates / metabolism
  • Plants / chemistry*
  • Plants / metabolism
  • Transcription Factors / metabolism


  • Inositol Phosphates
  • Phosphates
  • Transcription Factors