title: The synthesis of the rhamnogalacturonan II component 3-deoxy-D-manno-2-octulosonic acid (Kdo) is required for pollen tube growth and elongation.
abstract: 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.
authors.affiliation: INRA (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.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Delmas
authors.forename: Martial
authors.initials: M
authors.lastname: Séveno
authors.forename: Julian G B
authors.initials: JG
authors.lastname: Northey
authors.forename: Michel
authors.initials: M
authors.lastname: Hernould
authors.forename: Patrice
authors.initials: P
authors.lastname: Lerouge
authors.forename: Peter
authors.initials: P
authors.lastname: McCourt
authors.forename: Christian
authors.initials: C
authors.lastname: Chevalier
mesh_terms: D000446:Aldehyde-Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D018506:Gene Expression Regulation, Plant; D010368:Pectins / Q000737:chemistry / Q000378:metabolism*; D011058:Pollen / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013400:Sugar Acids / Q000378:metabolism*; D013403:Sugar Phosphates / Q000378:metabolism*
chemical_list: C415188:3-deoxyoctulosonate 8-phosphate; D029681:Arabidopsis Proteins; D020033:Protein Isoforms; D013400:Sugar Acids; D013403:Sugar Phosphates; C042492:rhamnogalacturonan II; D010368:Pectins; C020011:2-dehydro-3-deoxyphosphooctonate aldolase; D000446:Aldehyde-Lyases