The ARLA1A-NAC089 module coordinates ER phagy with the unfolded protein response to maintain cellular homeostasis in plants.

Abstract

The endoplasmic reticulum (ER) is a critical quality-control organelle for protein homeostasis within the cell. The accumulation of misfolded or unfolded proteins triggers ER stress, which can be alleviated through the unfolded protein response (UPR) and ER phagy. These processes work in concert to preserve ER homeostasis, yet the molecular interactions between them remain poorly understood in plants. In this study, we identify the ER-anchored transcription factor NAC089 as an ER-phagy receptor acting downstream of the ADP-ribosylation factor (ARF)-like (ARL) GTPase ARLA1A under carbon starvation. Furthermore, we demonstrate that active ARLA1A inhibits ER phagy by negatively regulating NAC089. Notably, the ARLA1A-NAC089 axis coordinates ER phagy with the UPR to balance cell survival and death. Our findings unveil a multi-layered regulatory network that is essential for maintaining cellular homeostasis and enhancing plant adaptation to environmental stresses.