Cargo Recognition and Function of Selective Autophagy Receptors in Plants

Abstract

Autophagy is a major quality control system for degradation of unwanted or damaged cytoplasmic components to promote cellular homeostasis. Although non-selective bulk degradation of cytoplasm by autophagy plays a role during cellular response to nutrient deprivation, the broad roles of autophagy are primarily mediated by selective clearance of specifically targeted components. Selective autophagy relies on cargo receptors that recognize targeted components and recruit them to autophagosomes through interaction with lapidated autophagy-related protein 8 (ATG8) family proteins anchored in the membrane of the forming autophagosomes. In mammals and yeast, a large collection of selective autophagy receptors have been identified that mediate the selective autophagic degradation of organelles, aggregation-prone misfolded proteins and other unwanted or nonnative proteins. A substantial number of selective autophagy receptors have also been identified and functionally characterized in plants. Some of the autophagy receptors in plants are evolutionarily conserved with homologs in other types of organisms, while a majority of them are plant-specific or plant species-specific. Plant selective autophagy receptors mediate autophagic degradation of not only misfolded, nonactive and otherwise unwanted cellular components but also regulatory and signaling factors and play critical roles in plant responses to a broad spectrum of biotic and abiotic stresses. In this review, we summarize the research on selective autophagy in plants, with an emphasis on the cargo recognition and the biological functions of plant selective autophagy receptors.

Autophagy in Plant Abiotic Stress Management

“…Almost all autophagy-related receptors/adaptors identified to date have ATG8 interaction domains (AIMs/UIMs) or can directly interact with ATG8. These results imply sophisticated roles of ATG8 in autophagy and plant development or stress response, which were illustrated in detail in recent reviews [55][56][57].…”

“…Autophagy was initially defined as a bulk degradation process that causes massive degradation of cellular components; however, in recent years, cumulative evidence has indicated that the recruitment of cargo to autophagosomes is highly selective [56,93]. Several selective autophagy receptors have been characterized in plants.…”

Control of ABA Signaling and Crosstalk with Other Hormones by the Selective Degradation of Pathway Components

“…The selectivity of autophagy is achieved due to the involvement of selective autophagy cargo receptors. They recognize cargo and dock to the autophagosomes [ 129 , 130 ]. Autophagy, in contrast to the 26S proteasome, can not only degrade proteins and protein aggregates, but also entire organelles or their parts.…”

Role of autophagy in gastric carcinogenesis

“…There are three subtypes of autophagy depending on the mechanisms transporting the substrates in the lysosomes: macro-autophagy, micro-autophagy and chaperone-mediated autophagy (CMA). Macro-autophagy (the principal form of autophagy) is developed in response to stress and targets the release and degradation of every kind of aggregated protein and dysfunctional organelle by inducing a specific form of cytosolic vesicles, the autophagosomes[ 30 ]; the core machinery of autophagosome formation requires more than 40 largely conserved ATG[ 31 ]. Micro-autophagy, a non-selective procedure, is activated commonly to ingest senescent endoplasmic membranes by direct engulfment in the lysosome membrane[ 32 ]; it is the only constitutive autophagy mechanism that triggers small cytoplasmic debris engulfment into the lysosome for degradation[ 31 ].…”