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BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Cell Wall Modifications in Arabidopsis Plants with Altered -L-Arabinofuranosidase Activity^[C],[W]

UMR 5546, CNRS-Université Paul Sabatier, Surfaces Cellulaires et Signalisation chez les Végétaux, BP 42617 Auzeville, 31326 Castanet-Tolosan, France (R.A.C.M., P.R., Y.M., A.J., D.G.); Laboratoire de Biologie Cellulaire, Institut National de la Recherche Agronomique, 78026 Versailles cedex, France (Z.M., L.J.); Biopolymères Interactions Assemblages, Unité de Recherche sur les Polysaccharides leurs Organisations et Interactions, Institut National de la Recherche Agronomique, BP 71627, 44316 Nantes cedex 03, France (M.M., L.S.); Department of Genetics, University of Melbourne, Victoria 3010, Australia (L.M.F., C.S.C.); and Unité de Recherche en Génomique Végétale, INRA-CNRS, CP 5708, 91057 Evry cedex, France (F.B., J.-P.R.)

Although cell wall remodeling is an essential feature of plant growth and development, the underlying molecular mechanisms are poorly understood. This work describes the characterization of Arabidopsis (Arabidopsis thaliana) plants with altered expression of ARAF1, a bifunctional -L-arabinofuranosidase/β-D-xylosidase (At3g10740) belonging to family 51 glycosyl-hydrolases. ARAF1 was localized in several cell types in the vascular system of roots and stems, including xylem vessels and parenchyma cells surrounding the vessels, the cambium, and the phloem. araf1 T-DNA insertional mutants showed no visible phenotype, whereas transgenic plants that overexpressed ARAF1 exhibited a delay in inflorescence emergence and altered stem architecture. Although global monosaccharide analysis indicated only slight differences in cell wall composition in both mutant and overexpressing lines, immunolocalization experiments using anti-arabinan (LM6) and anti-xylan (LM10) antibodies indicated cell type-specific alterations in cell wall structure. In araf1 mutants, an increase in LM6 signal intensity was observed in the phloem, cambium, and xylem parenchyma in stems and roots, largely coinciding with ARAF1 expression sites. The ectopic overexpression of ARAF1 resulted in an increase in LM10 labeling in the secondary walls of interfascicular fibers and xylem vessels. The combined ARAF1 gene expression and immunolocalization studies suggest that arabinan-containing pectins are potential in vivo substrates of ARAF1 in Arabidopsis.

² Present address: Entwicklungsbiologie der Pflanzen, Wissenschaftszentrum Weihenstephan, Technische Universität Munich, Am Hochanger 4, D–85354 Freising, Germany.

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: Deborah Goffner (goffner{at}scsv.ups-tlse.fr).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.110023

^* Corresponding author; e-mail goffner{at}scsv.ups-tlse.fr.

Received September 28, 2007; accepted March 13, 2008; published March 14, 2008.