Protein Quality Control in Plant Organelles: Current Progress and Future Perspectives

• Published in: Molecular plant Vol. 14; no. 1; pp. 95 - 114
• Main Authors: Sun, Jing-Liang, Li, Jin-Yu, Wang, Mei-Jing, Song, Ze-Ting, Liu, Jian-Xiang
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 04.01.2021
• Subjects: autophagy; chloroplast-associated protein degradation; chloroplasts; cytosol; endoplasmic reticulum; energy; ER-associated protein degradation; homeostasis; imports; mitochondria; mitochondria-associated protein degradation; photosynthesis; plant growth; protein degradation; protein folding; protein quality control; protein value; proteinases; proteins; quality control; stress tolerance; unfolded protein response; protein quality control; unfolded protein response; chloroplast-associated protein degradation; mitochondria-associated protein degradation; autophagy; ER-associated protein degradation
• ISSN: 1674-2052; 1752-9867; 1752-9867
• DOI: 10.1016/j.molp.2020.10.011

The endoplasmic reticulum, chloroplasts, and mitochondria are major plant organelles for protein synthesis, photosynthesis, metabolism, and energy production. Protein homeostasis in these organelles, maintained by a balance between protein synthesis and degradation, is essential for cell functions during plant growth, development, and stress resistance. Nucleus-encoded chloroplast- and mitochondrion-targeted proteins and ER-resident proteins are imported from the cytosol and undergo modification and maturation within their respective organelles. Protein folding is an error-prone process that is influenced by both developmental signals and environmental cues; a number of mechanisms have evolved to ensure efficient import and proper folding and maturation of proteins in plant organelles. Misfolded or damaged proteins with nonnative conformations are subject to degradation via complementary or competing pathways: intraorganelle proteases, the organelle-associated ubiquitin–proteasome system, and the selective autophagy of partial or entire organelles. When proteins in nonnative conformations accumulate, the organelle-specific unfolded protein response operates to restore protein homeostasis by reducing protein folding demand, increasing protein folding capacity, and enhancing components involved in proteasome-associated protein degradation and autophagy. This review summarizes recent progress on the understanding of protein quality control in the ER, chloroplasts, and mitochondria in plants, with a focus on common mechanisms shared by these organelles during protein homeostasis. Accumulation of misfolded proteins in plant organelles can cause dysfunctions that lead to developmental defects and impaired environmental stress tolerance. This review summarizes recent advances in the understanding of the mechanisms that safeguard protein quality in the ER, chloroplasts, and mitochondria, and highlights common mechanisms shared by these organelles that ensure protein homeostasis in plant cells.