A viable Arabidopsis pex13 missense allele confers severe peroxisomal defects and decreases PEX5 association with peroxisomes
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Peroxisomes are organelles that catabolize fatty acids and compartmentalize other oxidative metabolic processes in eukaryotes. Using a forward-genetic screen designed to recover severe peroxisome-defective mutants, we isolated a viable allele of the peroxisome biogenesis gene PEX13 with striking peroxisomal defects. The pex13-4 mutant requires an exogenous source of fixed carbon for pre-photosynthetic development and is resistant to the protoauxin indole-3-butyric acid. Delivery of peroxisome-targeted matrix proteins depends on the PEX5 receptor docking with PEX13 at the peroxisomal membrane, and we found severely reduced import of matrix proteins and less organelle-associated PEX5 in pex13-4 seedlings. Moreover, pex13-4 physiological and molecular defects were partially ameliorated when PEX5 was overexpressed, suggesting that PEX5 docking is partially compromised in this mutant and can be improved by increasing PEX5 levels. Because previously described Arabidopsis pex13 alleles either are lethal or confer only subtle defects, the pex13-4 mutant provides valuable insight into plant peroxisome receptor docking and matrix protein import.
KeywordsPeroxisome Organelle biogenesis Subcellular targeting
We thank Steven Smith (University of Western Australia) for the PMDH2 antibody, Monique Gill for assistance with the mutant screen, and Kim Gonzalez, Yun-Ting Kao, Mauro Rinaldi, and Pierce Young for critical comments on the manuscript. This research was supported by the National Science Foundation (MCB-1244182) and the Robert A. Welch Foundation (C-1309). Confocal microscopy was performed on equipment obtained through a Shared Instrumentation Grant from the National Institutes of Health (S10RR026399). A. W. W. was partially supported by a UMHB Faculty Development Grant, and M. B. was partially supported by a Howard Hughes Medical Institute Professors Grant (52005717 to B. B.).
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