Browsing by Author "Farmer, Lisa M."

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    Disrupting Autophagy Restores Peroxisome Function to an Arabidopsis lon2 Mutant and Reveals a Role for the LON2 Protease in Peroxisomal Matrix Protein Degradation
    (American Society of Plant Biologists, 2013) Farmer, Lisa M.; Rinaldi, Mauro A.; Young, Pierce G.; Danan, Charles H.; Burkhart, Sarah E.; Bartel, Bonnie
    Peroxisomes house critical metabolic reactions that are essential for seedling development. As seedlings mature, metabolic requirements change, and peroxisomal contents are remodeled. The resident peroxisomal protease LON2 is positioned to degrade obsolete or damaged peroxisomal proteins, but data supporting such a role in plants have remained elusive. Arabidopsis thaliana lon2 mutants display defects in peroxisomal metabolism and matrix protein import but appear to degrade matrix proteins normally. To elucidate LON2 functions, we executed a forward-genetic screen for lon2 suppressors, which revealed multiple mutations in key autophagy genes. Disabling core autophagy-related gene (ATG) products prevents autophagy, a process through which cytosolic constituents, including organelles, can be targeted for vacuolar degradation. We found that atg2, atg3, and atg7 mutations suppressed lon2 defects in auxin metabolism and matrix protein processing and rescued the abnormally large size and small number of lon2 peroxisomes. Moreover, analysis of lon2 atg mutants uncovered an apparent role for LON2 in matrix protein turnover. Our data suggest that LON2 facilitates matrix protein degradation during peroxisome content remodeling, provide evidence for the existence of pexophagy in plants, and indicate that peroxisome destruction via autophagy is enhanced when LON2 is absent.
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    Mutation of the Arabidopsis LON2 peroxisomal protease enhances pexophagy
    (Landes Bioscience, 2014) Bartel, Bonnie; Farmer, Lisa M.; Rinaldi, Mauro A.; Young, Pierce G.; Danan, Charles H.; Burkhart, Sarah E.
    Peroxisomes are critical organelles housing various, often oxidative, reactions. Pexophagy, the process by which peroxisomes are selectively targeted for destruction via autophagy, is characterized in yeast and mammals but had not been reported in plants. In this article, we describe how the peroxisome-related aberrations of a mutant defective in the LON2 peroxisomal protease are suppressed when autophagy is prevented by mutating any of several key autophagy-related (ATG) genes. Our results reveal that plant peroxisomes can be degraded by selective autophagy and suggest that pexophagy is accelerated when the LON2 protease is disabled.