Plant and Cell Physiology Advance Access originally published online on May 3, 2007
Plant and Cell Physiology 2007 48(6):763-774; doi:10.1093/pcp/pcm053
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Functional Classification of Arabidopsis Peroxisome Biogenesis Factors Proposed from Analyses of Knockdown Mutants
1Department of Cell Biology, National Institute for Basic Biology, Okazaki, 444-8585 Japan
2Department of Molecular Biomechanics, School of Life Science, The Graduate University for Advanced Studies, Okazaki, 444-8585 Japan
*Corresponding author: E-mail, mikosome{at}nibb.ac.jp; Fax, +81-564-55-7505.
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Abstract |
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In higher plants, peroxisomes accomplish a variety of physiological functions such as lipid catabolism, photorespiration and hormone biosynthesis. Recently, many factors regulating peroxisomal biogenesis, so-called PEX genes, have been identified not only in plants but also in yeasts and mammals. In the Arabidopsis genome, the presence of at least 22 PEX genes has been proposed. Here, we clarify the physiological functions of 18 PEX genes for peroxisomal biogenesis by analyzing transgenic Arabidopsis plants that suppressed the PEX gene expression using RNA interference. The results indicated that the function of these PEX genes could be divided into two groups. One group involves PEX1, PEX2, PEX4, PEX6, PEX10, PEX12 and PEX13 together with previously characterized PEX5, PEX7 and PEX14. Defects in these genes caused loss of peroxisomal function due to misdistribution of peroxisomal matrix proteins in the cytosol. Of these, the pex10 mutant showed pleiotropic phenotypes that were not observed in any other pex mutants. In contrast, reduced peroxisomal function of the second group, including PEX3, PEX11, PEX16 and PEX19, was induced by morphological changes of the peroxisomes. Cells of the pex16 mutant in particular possessed reduced numbers of large peroxisome(s) that contained unknown vesicles. These results provide experimental evidence indicating that all of these PEX genes play pivotal roles in regulating peroxisomal biogenesis. We conclude that PEX genes belonging to the former group are involved in regulating peroxisomal protein import, whereas those of the latter group are important in maintaining the structure of peroxisome.
Keywords: Double-Stranded RNA interference - Glyoxysome - Peroxin - Peroxisome biogenesis - PEX - Protein targeting
Abbreviations: 2,4-DB, 2,4-dichlorophenoxybutyric acid; dsRNAi, double-stranded RNA interference; GFP, green fluorescent protein; PEX, peroxisome biogenesis factor, PTS, peroxisomal targeting signal.
(Received February 27, 2007; Accepted April 27, 2007)
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