ARSK1 activates TORC1 signaling to adjust growth to phosphate availability in Arabidopsis

Nutrient sensing and signaling are essential for adjusting growth and development to available resources. Deprivation of the essential mineral phosphorus (P) inhibits root growth.1 The molecular processes that sense P limitation to trigger early root growth inhibition are not known yet. Target of rapamycin (TOR) kinase is a central regulatory hub in eukaryotes to adapt growth to internal and external nutritional cues.2,3 How nutritional signals are transduced to TOR to control plant growth remains unclear. Here, we identify Arabi-dopsis-root-specific kinase 1 (ARSK1), which attenuates initial root growth inhibition in response to P limita-tion. We demonstrate that ARSK1 phosphorylates and stabilizes the regulatory-associated protein of TOR 1B (RAPTOR1B), a component of the TOR complex 1, to adjust root growth to P availability. These findings uncover signaling components acting upstream of TOR to balance growth to P availability.

Automated summary

Nutrient sensing and signaling play a crucial role in adapting growth to available resources. However, the molecular processes involved in sensing and responding to phosphorus (P) limitation to inhibit root growth are still unclear. In this study, the researchers identified a kinase called ARSK1 that attenuates early root growth inhibition under P limitation. They also discovered that ARSK1 phosphorylates and stabilizes RAPTOR1B, a component of TOR complex 1, to regulate root growth in response to P availability. These findings provide insights into the signaling components that regulate growth in relation to P availability.