Abstract
Autophagy is an evolutionarily conserved process that occurs in yeast, plants, and animals. Despite many years of research, some aspects of autophagy are still not fully explained. This mostly concerns the final stages of autophagy, which have not received as much interest from the scientific community as the initial stages of this process. The final stages of autophagy that we take into consideration in this review include the formation and degradation of the autophagic bodies as well as the efflux of metabolites from the vacuole to the cytoplasm. The autophagic bodies are formed through the fusion of an autophagosome and vacuole during macroautophagy and by vacuolar membrane invagination or protrusion during microautophagy. Then they are rapidly degraded by vacuolar lytic enzymes, and products of the degradation are reused. In this paper, we summarize the available information on the trafficking of the autophagosome towards the vacuole, the fusion of the autophagosome with the vacuole, the formation and decomposition of autophagic bodies inside the vacuole, and the efflux of metabolites to the cytoplasm. Special attention is given to the formation and degradation of autophagic bodies and metabolite salvage in plant cells.
Highlights
Autophagy, which literally means “self-eating”, plays a crucial role in the degradation of useless or damaged cell components such as macromolecules, protein complexes, and organelles
References activation of protease and hydrolase cascades by proteolytic processing degradation of autophagic body, decomposition and recycling of autophagic body membrane, proaminopeptidase I maturation tonoplast protein with limited homology to permeases, putative vacuolar transporter involved in the efflux of metabolites from the vacuole to the cytoplasm probably degradation of the autophagic body vacuolar efflux transporters potentially involved in the efflux of leucine and other amino acids derived from the degradation of the autophagic body probably autocatalytically converted into a smaller active form, which, like yeast’s Pep4, might be involved in proteolytically downstream processes that are responsible for the degradation of various vacuolar constituents vacuolar efflux transporter potentially involved in the efflux of metabolites derived from the degradation of the autophagic body
The events occurring in the final stages of autophagy have been explored only marginally and require a lot of research to be fully understood
Summary
Autophagy, which literally means “self-eating”, plays a crucial role in the degradation of useless or damaged cell components such as macromolecules, protein complexes, and organelles. Only the involvement of protein VTI12 has been confirmed in the fusion of autophagosome and vacuole in plants (Figure 3, Table 1). This protein belongs to the complex named. In Arabidopsis mutants with T-DNA VTI12 insertion, growing in rich-nutrient conditions, presented a normal phenotype, whereas under nutrient-poor conditions accelerated aging was observed, confirming that VTI12 is involved in autophagy in plants [25,74,75,76,77] This protein participates in the transport of storage proteins from the cytoplasm to the vacuole [76]. Function autophagosome trafficking and fusion autophagosome formation, autophagosome-vacuole fusion retrograde transport, vacuole homotypic fusion, vesicles and vacuole fusion endosome-autophagosome fusion, autophagosome maturation, autophagosome-vacuole docking and fusion autophagosome-vacuole fusion autophagosome-vacuole fusion autophagosome-vacuole fusion probably autophagosome-vacuole fusion probably autophagosome formation, docking, and autophagosome-vacuole fusion, storage protein transport from cytoplasm to vacuole autophagy enhancement during xylem development and pathogen-induced cell death, probably autophagosome formation and autophagosome-vacuole fusion probably autophagic trafficking, autophagosome-vacuole fusion, release of autophagic body
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