PMID:19748917

Citation	Lingard, MJ and Bartel, B (2009) Arabidopsis LON2 is necessary for peroxisomal function and sustained matrix protein import. Plant Physiol. 151:1354-65
Abstract	Relatively little is known about the small subset of peroxisomal proteins with predicted protease activity. Here, we report that the peroxisomal LON2 (At5g47040) protease facilitates matrix protein import into Arabidopsis (Arabidopsis thaliana) peroxisomes. We identified T-DNA insertion alleles disrupted in five of the nine confirmed or predicted peroxisomal proteases and found only two-lon2 and deg15, a mutant defective in the previously described PTS2-processing protease (DEG15/At1g28320)-with phenotypes suggestive of peroxisome metabolism defects. Both lon2 and deg15 mutants were mildly resistant to the inhibitory effects of indole-3-butyric acid (IBA) on root elongation, but only lon2 mutants were resistant to the stimulatory effects of IBA on lateral root production or displayed Suc dependence during seedling growth. lon2 mutants displayed defects in removing the type 2 peroxisome targeting signal (PTS2) from peroxisomal malate dehydrogenase and reduced accumulation of 3-ketoacyl-CoA thiolase, another PTS2-containing protein; both defects were not apparent upon germination but appeared in 5- to 8-d-old seedlings. In lon2 cotyledon cells, matrix proteins were localized to peroxisomes in 4-d-old seedlings but mislocalized to the cytosol in 8-d-old seedlings. Moreover, a PTS2-GFP reporter sorted to peroxisomes in lon2 root tip cells but was largely cytosolic in more mature root cells. Our results indicate that LON2 is needed for sustained matrix protein import into peroxisomes. The delayed onset of matrix protein sorting defects may account for the relatively weak Suc dependence following germination, moderate IBA-resistant primary root elongation, and severe defects in IBA-induced lateral root formation observed in lon2 mutants.
Links	PubMed PMC2773057 Online version:10.1104/pp.109.142505
Keywords	Arabidopsis/enzymology; Arabidopsis/genetics; Arabidopsis Proteins/genetics; Arabidopsis Proteins/metabolism; DNA, Bacterial; Gene Expression Regulation, Plant; Indoles/pharmacology; Peptide Hydrolases/genetics; Peptide Hydrolases/metabolism; Peroxisomes/metabolism; Plant Roots/growth & development; Protein Transport; Receptors, Cytoplasmic and Nuclear/metabolism; Serine Endopeptidases/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ARATH:LONP2	acts_upstream_of_or_within	GO:0016560: protein import into peroxisome matrix, docking	ECO:0000314: direct assay evidence used in manual assertion		P		Seeded From UniProt	complete
ARATH:LONP2	located_in	GO:0070013: intracellular organelle lumen	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
ARATH:LONP2	acts_upstream_of_or_within	GO:0048527: lateral root development	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

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