Two bifunctional inositol pyrophosphate kinases/phosphatases control plant phosphate homeostasis

Elife. 2019 Aug 22;8:e43582. doi: 10.7554/eLife.43582.

Abstract

Many eukaryotic proteins regulating phosphate (Pi) homeostasis contain SPX domains that are receptors for inositol pyrophosphates (PP-InsP), suggesting that PP-InsPs may regulate Pi homeostasis. Here we report that deletion of two diphosphoinositol pentakisphosphate kinases VIH1/2 impairs plant growth and leads to constitutive Pi starvation responses. Deletion of phosphate starvation response transcription factors partially rescues vih1 vih2 mutant phenotypes, placing diphosphoinositol pentakisphosphate kinases in plant Pi signal transduction cascades. VIH1/2 are bifunctional enzymes able to generate and break-down PP-InsPs. Mutations in the kinase active site lead to increased Pi levels and constitutive Pi starvation responses. ATP levels change significantly in different Pi growth conditions. ATP-Mg2+ concentrations shift the relative kinase and phosphatase activities of diphosphoinositol pentakisphosphate kinases in vitro. Pi inhibits the phosphatase activity of the enzyme. Thus, VIH1 and VIH2 relay changes in cellular ATP and Pi concentrations to changes in PP-InsP levels, allowing plants to maintain sufficient Pi levels.

Keywords: A. thaliana; S. cerevisiae; biochemistry; chemical biology; human; inositol pyrophosphates; kinase; phosphatase; phosphate homeostasis; phosphate starvation; plant biology; plant nutrition.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Arabidopsis / enzymology*
  • Arabidopsis / metabolism*
  • Diphosphates / metabolism*
  • Gene Deletion
  • Homeostasis
  • Phosphotransferases (Phosphate Group Acceptor) / genetics
  • Phosphotransferases (Phosphate Group Acceptor) / metabolism*

Substances

  • Diphosphates
  • Adenosine Triphosphate
  • Phosphotransferases (Phosphate Group Acceptor)
  • diphosphoinositol pentakisphosphate kinase