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Title: Disparate peroxisome‐related defects in Arabidopsis pex6 and pex26 mutants link peroxisomal retrotranslocation and oil body utilization

Catabolism of fatty acids stored in oil bodies is essential for seed germination and seedling development in Arabidopsis. This fatty acid breakdown occurs in peroxisomes, organelles that sequester oxidative reactions. Import of peroxisomal enzymes is facilitated by peroxins includingPEX5, a receptor that delivers cargo proteins from the cytosol to the peroxisomal matrix. After cargo delivery, a complex of thePEX1 andPEX6ATPases and thePEX26 tail‐anchored membrane protein removes ubiquitinatedPEX5 from the peroxisomal membrane. We identified Arabidopsispex6andpex26mutants by screening for inefficient seedling β‐oxidation phenotypes. The mutants displayed distinct defects in growth, response to a peroxisomally metabolized auxin precursor, and peroxisomal protein import. The lowPEX5 levels in these mutants were increased by treatment with a proteasome inhibitor or by combiningpex26with peroxisome‐associated ubiquitination machinery mutants, suggesting that ubiquitinatedPEX5 is degraded by the proteasome when the function ofPEX6 orPEX26 is reduced. Combiningpex26with mutations that increasePEX5 levels either worsened or improvedpex26physiological and molecular defects, depending on the introduced lesion. Moreover, elevatingPEX5 levels via a35S:PEX5transgene exacerbatedpex26defects and ameliorated the defects of only a subset ofpex6alleles, implying that decreasedPEX5 is not the sole molecular deficiency in these mutants. We found peroxisomes clustered around persisting oil bodies inpex6andpex26seedlings, suggesting a role for peroxisomal retrotranslocation machinery in oil body utilization. The disparate phenotypes of thesepexalleles may reflect unanticipated functions of the peroxisomalATPase complex.

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Author(s) / Creator(s):
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Publisher / Repository:
Date Published:
Journal Name:
The Plant Journal
Page Range / eLocation ID:
p. 110-128
Medium: X
Sponsoring Org:
National Science Foundation
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