Inositol Pyrophosphates and Phosphate Sensing in Plants

Abstract

Phosphate (Pi) is an essential nutrient for plants, required for plant growth and seed viability. Under Pi stress, plants undergo dynamic changes to leverage available Pi. One class of signaling molecules implicated in the Pi sensing pathway is the inositol pyrophosphates (PPx‐InsPs). PPx‐InsPs have high energy bonds, and have been linked to maintaining Pi and energy homeostasis in plants, yeast, and humans. In plants, PPx‐InsPs are thought to function in sensing Pi changes by binding to proteins containing an SPX domain. One particular SPX protein binds to PPx‐InsPs which prevents a transcription factor from activating transcription of the so‐called phosphate starvation response (PSR) genes. Plants are known to accumulate two common PPx‐InsPs, PP‐InsP5 (called InsP7) and PP2‐InsP4 (called InsP8), but the synthesis pathway has not yet been elucidated. We have identified and characterized the plant VIP kinases, enzymes that likely function as PP‐InsP5 kinases. The identity of a plant inositol kinase that can phosphorylate InsP6, resulting in PP‐InsP5, however, has remained elusive. We will describe our recent results in characterizing this pathway, and genetic mutants key for understanding inositol kinase gene function in plants. Our results support a model in which InsP7 and InsP8 function to turn off the PSR in plants.Support or Funding InformationThis work was supported by an award from the NSF to GG and IP:MCB 1615953This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.