Autophagy Contributes to the Quality Control of Leaf Mitochondria

Abstract

In autophagy, cytoplasmic components of eukaryotic cells are transported to lysosomes or the vacuole for degradation. Autophagy is involved in plant tolerance to the photooxidative stress caused by ultraviolet B (UVB) radiation, but its roles in plant adaptation to UVB damage have not been fully elucidated. Here, we characterized organellar behavior in UVB-damaged Arabidopsis (Arabidopsis thaliana) leaves and observed the occurrence of autophagic elimination of dysfunctional mitochondria, a process termed mitophagy. Notably, Arabidopsis plants blocked in autophagy displayed increased leaf chlorosis after a 1-h UVB exposure compared to wild-type plants. We visualized autophagosomes by labeling with a fluorescent protein-tagged autophagosome marker, AUTOPHAGY8 (ATG8), and found that a 1-h UVB treatment led to increased formation of autophagosomes and the active transport of mitochondria into the central vacuole. In atg mutant plants, the mitochondrial population increased in UVB-damaged leaves due to the cytoplasmic accumulation of fragmented, depolarized mitochondria. Furthermore, we observed that autophagy was involved in the removal of depolarized mitochondria when mitochondrial function was disrupted by mutation of the FRIENDLY gene, which is required for proper mitochondrial distribution. Therefore, autophagy of mitochondria functions in response to mitochondrion-specific dysfunction as well as UVB damage. Together, these results indicate that autophagy is centrally involved in mitochondrial quality control in Arabidopsis leaves.

The core autophagy machinery is not required for chloroplast singlet oxygen-mediated cell death in the Arabidopsis thaliana plastid ferrochelatase two mutant

“…The vector containing the UBQ10 :: GFP-ATG8a construct (At4g21980.1 [ 72 ]) was transformed into the A. tumefaciens strain GV3101, which was subsequently used to transform Arabidopsis via the floral dip method. T 1 plants were selected for their ability to grow on Basta-soaked soil and propagated to the next generation.…”

Contribution of Massive Mitochondrial Fusion and Subsequent Fission in the Plant Life Cycle to the Integrity of the Mitochondrion and Its Genome

“…What is implied here is that in the cell cycle is a type of surveillance mechanism for mitophagy. However, mitophagy and its regulation have been predominantly investigated in the context of a range of stressors, such as UV light [ 80 ], and senescence [ 76 , 77 , 78 , 79 ]. Interestingly, recent work has implicated the FRIENDLY protein, linked to mitochondrial fusion because of its clustering role, in mitophagy.…”

How Lipids Contribute to Autophagosome Biogenesis, a Critical Process in Plant Responses to Stresses

“…During their life cycle, plants are also subjected to longer or shorter photoperiods depending on the seasons but also to variable light spectral qualities including visible light (400–700 nm) and ultraviolet-B (UV-B; 280–315 nm), the most energetic wavelength light reaching the surface of the Earth [ 66 , 67 ]. A strong and prolonged exposure to either visible light or UV-B can lead to large damage of plants macromolecules (DNA, proteins and lipids).…”

“…A strong and prolonged exposure to either visible light or UV-B can lead to large damage of plants macromolecules (DNA, proteins and lipids). Recently it was shown that the atg2 , atg5 , atg7 , atg10 , atg12a, and atg18a mutants were hypersensitive to a treatment with UV-B leading to a half reduction in the activity of PSII in comparison with the WT [ 66 , 67 ]. A high visible light treatment also induced a necrosis phenotype in the atg2-1 mutant [ 60 ].…”