Eat at the right time: Regulation of ER-phagy receptors in plant response to environmental stresses

Abstract

The endoplasmic reticulum (ER) is the site where proteins and lipids are made. Recent research has spotlighted ER-phagy, a selective autophagy of the ER, as an important player in plant adaptation to environmental stresses. Central to ER-phagy are diverse ER-phagy receptors in both mammalian and plant cells that not only facilitate the selective degradation of the ER but also participate in the formation of the ER under normal conditions. How do cells modulate these two actions of ER-phagy receptors? Recent studies suggest that three post-translational modifications: ubiquitination, phosphorylation and UFMylation, may act as switches for these dual roles. Given the importance of ER-phagy in plant stress responses, understanding the factors that govern these dual functions is crucial. Here we seek to integrate recent research in ER-phagy receptors in mammalian and plant cells. We hypothesize that ubiquitination and phosphorylation operate collaboratively in plant cells to determine action of ER-phagy receptors in tubular ER-phagy, while UFMylation acts in rough/sheet ER-phagy. We also suggest the need for further investigations into the specificity of ER-phagy receptors and signal pathways that relay environmental stresses to the two post-translational modifications of ER-phagy receptors.