JXB Advance Access originally published online on May 23, 2008
Journal of Experimental Botany 2008 59(10):2639-2647; doi:10.1093/jxb/ern118
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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RESEARCH PAPER |
The synthesis of the rhamnogalacturonan II component 3-deoxy-D-manno-2-octulosonic acid (Kdo) is required for pollen tube growth and elongation
1INRA (Institut National de la Recherche Agronomique), Unité Mixte de Recherche 619 sur la Biologie du Fruit, Institut Fédératif de Recherche 103, F-33883 Villenave d'Ornon, France
2Université Victor Segalen Bordeaux 2, Unité Mixte de Recherche 619 sur la Biologie du Fruit, Institut Fédératif de Recherche 103, F-33883 Villenave d'Ornon, France
3Centre National de la Recherche Scientifique, Unité Mixte de Recherche 6037, Laboratoire des Transports Intracellulaires, IFRMP 23, Université de Rouen, F-76821 Mont Saint Aignan, France
4University of Toronto, Cell and Systems Biology Laboratory, 25 Willcocks Street, Toronto, Ontario M5S3B2, Canada
* To whom correspondence should be addressed. E-mail: chevalie{at}bordeaux.inra.fr
Despite a very complex structure, the sugar composition of the rhamnogalacturonan II (RG-II) pectic fraction is extremely conserved. Among its constituting monosaccharides is the seldom-observed eight-carbon sugar 3-deoxy-D-manno-octulosonic acid (Kdo), whose phosphorylated precursor is synthesized by Kdo-8-P synthase. As an attempt to alter specifically the RG-II structure in its sugar composition and assess the consequences on the function of RG-II in cell wall and its relationship with growth, Arabidopsis null mutants were sought in the genes encoding Kdo-8-P synthase. Here, the isolation and characterization of one null mutant for the isoform 1 (AtkdsA1-S) and two distinct null mutants for the isoform 2 of Arabidopsis Kdo-8-P synthase (AtkdsA2-V and AtkdsA2-S) are described. Evidence is provided that AtkdsA2 gene expression is preferentially associated with plantlet organs displaying a meristematic activity, and that it accounts for 75% of the mRNAs to be translated into Kdo-8-P synthase. Furthermore, this predominant expression of AtKDSA2 over AtKDSA1 was confirmed by quantification of the cytosolic Kdo content in the mutants, in a variety of ecotypes. The inability to identify a double knockout mutant originated from pollen abortions, due to the inability of haploid pollen of the AtkdsA1- AtkdsA2- genotype to form an elongated pollen tube properly and perform fertilization.
Key words: Arabidopsis thaliana, 3-deoxy-D-manno-oct-2-ulosonate-8-phosphate, 3-deoxy-D-manno-oct-2-ulosonate-8-phosphate synthase, pollen tube growth, rhamnogalacturonan II
Received 5 February 2008; Accepted 2 April 2008