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

Abstract

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.

Keywords: Arabidopsis; PIN FORMED1; VPS36; endosomal sorting complexes required for transport (ESCRT); root gravitropism.

Figure 1.

VPS36 is involved in gravitropism. (A) Seven-day-old phenotype and qPCR analysis of 3 VPS36 RNAi lines under estrogen treatment. VPS36 RNAi plants were grown on half-strength MS medium containing DMSO or 8 µM estrogen for 7 d. Data are mean ± SD. (B) PIN1 accumulation in the intracellular compartment of VPS36 RNAi plants after 8 µM estrogen treatment. The cell wall was stained with propidium iodide, shown in red. (C) Root bending in wild-type and VPS36 RNAi plants after gravistimulation. Seeds of VPS36 RNAi were germinated on half-strength MS medium containing DMSO or 8 µM estrogen for 7 d. Seven-day-old seedlings were transferred to half-strength MS medium and grown vertically for another day.