The TOR–Auxin Connection Upstream of Root Hair Growth

The review discussed the intricate relationship between TARGET OF RAPAMYCIN (TOR) signaling and auxin distribution in regulating root hair growth in plants. High energy levels led to increased auxin biosynthesis, activating TOR signaling through RHO-RELATED PROTEIN FROM PLANTS 2 (ROP2), which promoted root hair cell priming and elongation. Conversely, low energy levels triggered the SNF1-RELATED KINASE 1 (SnRK1) complex, deactivating TOR and halting root growth. The auxin efflux carrier PIN-FORMED 2 (PIN2) was essential for transporting auxin to root hair cells. The review highlighted the dynamic interplay between TOR signaling, auxin distribution, and environmental conditions in root hair development, emphasizing the need for further research under natural growth conditions.