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First published online February 24, 2006; 10.1104/pp.105.074997 Plant Physiology 140:1406-1417 (2006) © 2006 American Society of Plant Biologists
The reb1-1 Mutation of Arabidopsis. Effect on the Structure and Localization of Galactose-Containing Cell Wall Polysaccharides1,[W]Unité Mixte de Recherche, Centre National de la Recherche Scientifique 6037, Federal Institute of Multidisciplinary Research on Peptides 23, Université de Rouen, 76 821 Mont Saint Aignan cedex, France (E.N.-O., C. A.-O., S. A.-A., M.B., P.L., A.D.); and Forestry and Forest Products Research Institute, Tsukuba Norin Kenkyu Danchi-nai, Ibaraki 305–8687, Japan (T.I.)
The Arabidopsis (Arabidopsis thaliana) root epidermal bulger1-1 (reb1-1) mutant (allelic to root hair defective1 [rhd1]) is characterized by a reduced root elongation rate and by bulging of trichoblast cells. The REB1/RHD1 gene belongs to a family of UDP-D-Glucose 4-epimerases involved in the synthesis of D-Galactose (Gal). Our previous study showed that certain arabinogalactan protein epitopes were not expressed in bulging trichoblasts of the mutant. In this study, using a combination of microscopical and biochemical methods, we have investigated the occurrence and the structure of three major Gal-containing polysaccharides, namely, xyloglucan (XyG), rhamnogalacturonan (RG)-I, and RG-II in the mutant root cell walls. Our immunocytochemical data show that swollen trichoblasts were not stained with the monoclonal antibody CCRC-M1 specific for
1 This work was supported by the Centre National de la Recherche Scientifique and the University of Rouen (to A.D.) and by the "PROBRAIN" (to T. I.). 2 These authors contributed equally to the paper. 3 Present address: Department of Molecular and Cellular and Developmental Biology, University of Colorado, Boulder, CO 80309–0347. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Azeddine Driouich (azeddine.driouich{at}univ-rouen.fr). [W] The online version of this article contains Web-only data. Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.105.074997. * Corresponding author; e-mail azeddine.driouich{at}univ-rouen.fr; fax 33–235146615. Received December 2, 2005; returned for revision February 14, 2006; accepted February 14, 2006. This article has been cited by other articles:
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-L-Fucp-(1
2)-
-D-Galp side chains of XyG, whereas they were stained with anti-XyG antibodies specific for XyG backbone. In addition, analysis of a hemicellulosic fraction from roots demonstrates the presence of two structurally different XyGs in reb1-1. One is structurally similar to wild-type XyG and the other is devoid of fuco-galactosylated side chains and has the characteristic of being insoluble. Similar to anti-XyG antibodies, anti-bupleuran 2IIC, a polyclonal antibody specific for galactosyl epitopes associated with pectins, stained all root epidermal cells of both wild type and reb1-1. Similarly, anti-RG-II antibodies also stained swollen trichoblasts in the mutant. In addition, structural analysis of pectic polymers revealed no change in the galactosylation of RG-I and RG-II isolated from reb1-1 root cells. These findings demonstrate that the reb1-1 mutation affects XyG structure, but not that of pectic polysaccharides, thus lending support to the hypothesis that biosynthesis of Gal as well as galactosylation of complex polysaccharides is regulated at the polymer level. 
