VPS36-Mediated plasma membrane protein turnover is critical for Arabidopsis root gravitropism

The gravitropic response is an evolutionary adaptation for plants to cope with the altered gravitational field. It involves reestablishing the distribution of the phytohormone auxin by differential degradation of auxin influx and efflux carriers. This process includes the endosomal sorting complexes required for transport (ESCRT) machinery to recognize ubiquitinated proteins and deliver them to vacuoles for degradation, as evidenced by vps36-1 mutants. Here, we generated RNAi knockdown plants of Vacuolar Protein Sorting 36 (VPS36) that could survive to adulthood. VPS36-induced RNAi plants showed PIN FORMED1 (PIN1) accumulation in the intracellular compartment, reduced root length and small stature, as observed in vps36-1 mutants. After gravistimulation, the roots of VPS36-induced RNAi plants did not show the bending observed in wild-type plants. The VPS36-containing ESCRT machinery may have a role in the gravitropic response possibly associated with the degradation of auxin transporters.