Journal Article

The synthesis of the rhamnogalacturonan II component 3-deoxy-<span class="smallCaps">D</span>-<i>manno</i>-2-octulosonic acid (Kdo) is required for pollen tube growth and elongation

Frédéric Delmas, Martial Séveno, Julian G. B. Northey, Michel Hernould, Patrice Lerouge, Peter McCourt and Christian Chevalier

in Journal of Experimental Botany

Published on behalf of Society for Experimental Biology

Volume 59, issue 10, pages 2639-2647
Published in print July 2008 | ISSN: 0022-0957
Published online May 2008 | e-ISSN: 1460-2431 | DOI: http://dx.doi.org/10.1093/jxb/ern118

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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.

Keywords: 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

Journal Article.  5290 words.  Illustrated.

Subjects: Plant Sciences and Forestry

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