Cargo receptors and adaptors for selective autophagy in plant cells

Abstract

Plant selective (macro)autophagy is a highly regulated process where eukaryotic cells spatiotemporally degrade some of their constituents that have become superfluous or harmful. The identification and characterization of the factors determining this selectivity make it possible to integrate selective (macro)autophagy into plant cell physiology and homeostasis. The specific cargo receptors and/or scaffold proteins involved in this pathway are generally not structurally conserved, as are the biochemical mechanisms underlying recognition and integration of a given cargo into the autophagosome in different cell types. This review discusses the few specific cargo receptors described in plant cells to highlight key features of selective autophagy in the plant kingdom and its integration with plant physiology, aiming to identify evolutionary convergence and knowledge gaps to be filled by future research.

Picky eaters: selective autophagy in plant cells

“…PEX3, PEX5, PEX6, PEX10, and PEX14 have been implicated in the autophagic degradation of peroxisomes and their interaction with ATG8 (Gonzalez et al., 2018; Xie et al., 2016; Young & Bartel, 2016). Although specific receptors for pexophagy in plants have not been reported, emerging candidates such as NBR1 have shown promise, potentially playing a dual role in regulating both proteaphagy and pexophagy (Luong et al., 2022). Ubiquitination has been implicated in peroxisome degradation, evidenced by the ubiquitination of 56 peroxisomal proteins associated with essential peroxisomal pathways related to photorespiration and ROS detoxification.…”

“…Nutrient starvation has also been shown to recruit specific ATG proteins associated with autophagy activation. In Arabidopsis, the recruitment of AtATG11 into the outer membrane of the mitochondria leads to ATG1 phosphorylation and degradation of the ATG activation complex, providing insights into the possible role of ATG11 in mitophagy and bulk autophagy (Li et al., 2014; Luong et al., 2022).…”

Autophagic degradation of membrane-bound organelles in plants

“…Here, unless otherwise specified, autophagy refers to macroautophagy, as in plants degradation of membrane-bound organelles, the focus of this review, generally occurs via macroautophagy. Selective autophagy of organelles in plants includes ER-phagy, mitophagy, pexophagy and chlorophagy, and requires specific recognition between receptors and their cargo [ 8 ]. ATG8 (called LC3 in mammals) is a critical factor that is recruited to and tethered on the membrane of autophagosomes via covalent conjugation to the membrane lipid phosphatidylethanolamine.…”

Plant autophagy and intracellular trafficking

“…Selectivity requires a receptor that specifically binds to a given cargo and also to the autophagosome protein ATG8, leading to selective incorporation of the cargo into the autophagosome [6]. Luong et al [7] describe the types of selective autophagy identified in plants, based on the cargo and receptors, including degradation of membrane-bound organelles, large protein structures, pathogens and individual proteins. They also compare the pathways and receptors for selective autophagy in plants with those known in yeast and mammals.…”

“…Luong et al. [7] describe the types of selective autophagy identified in plants, based on the cargo and receptors, including degradation of membrane‐bound organelles, large protein structures, pathogens and individual proteins. They also compare the pathways and receptors for selective autophagy in plants with those known in yeast and mammals.…”