Abstract
Peroxisomes are essential organelles that are characterized by the possession of enzymes that produce hydrogen peroxide (H2O2) as part of their normal catalytic cycle. During the metabolic process, peroxisomal proteins are inevitably damaged by H2O2 and the integrity of the peroxisomes is impaired. Here, we show that autophagy, an intracellular process for vacuolar degradation, selectively degrades dysfunctional peroxisomes. Marked accumulation of peroxisomes was observed in the leaves but not roots of autophagy-related (ATG)-knockout Arabidopsis thaliana mutants. The peroxisomes in leaf cells contained markedly increased levels of catalase in an insoluble and inactive aggregate form. The chemically inducible complementation system in ATG5-knockout Arabidopsis provided the evidence that these accumulated peroxisomes were delivered to vacuoles for degradation by autophagy. Interestingly, autophagosomal membrane structures specifically recognized the abnormal peroxisomes at the site of the aggregates. Thus, autophagy is essential for the quality control of peroxisomes in leaves and for proper plant development under natural growth conditions.
Highlights
Peroxisomes are essential organelles characterized by the possession of enzymes that produce hydrogen peroxide (H2O2) as part of their normal catalytic cycle (De Duve and Baudhuin, 1966)
We investigated the behavior of peroxisomes in ATGknockout Arabidopsis thaliana expressing green fluorescent protein (GFP) fused with PTS1 (Mano et al, 2002), a peroxisomal targeting signal
The number of peroxisomes was increased in the leaves of all atg mutants examined (Fig. 1A, upperright panel; Fig. 1B; supplementary material Fig. S1A,B)
Summary
Peroxisomes are essential organelles characterized by the possession of enzymes that produce hydrogen peroxide (H2O2) as part of their normal catalytic cycle (De Duve and Baudhuin, 1966). The number of peroxisomes was increased in the leaves of all atg mutants examined (Fig. 1A, upperright panel; Fig. 1B; supplementary material Fig. S1A,B). There was no obvious difference in the number of peroxisomes in roots between wild-type plants and atg mutants (Fig. 1A, lower panels; supplementary material Fig. S1C,D).
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