title: Two cell wall associated peroxidases from Arabidopsis influence root elongation.
abstract: Two class III peroxidases from Arabidopsis, AtPrx33 and Atprx34, have been studied in this paper. Their encoding genes are mainly expressed in roots; AtPrx33 transcripts were also found in leaves and stems. Light activates the expression of both genes in seedlings. Transformed seedlings producing AtPrx33-GFP or AtPrx34-GFP fusion proteins under the control of the CaMV 35S promoter exhibit fluorescence in the cell walls of roots, showing that the two peroxidases are localized in the apoplast, which is in line with their affinity for the Ca(2+)-pectate structure. The role they can play in cell wall was investigated using (1) insertion mutants that have suppressed or reduced expression of AtPrx33 or AtPrx34 genes, respectively, (2) a double mutant with no AtPrx33 and a reduced level of Atprx34 transcripts, (3) a mutant overexpressing AtPrx34 under the control of the CaMV 35S promoter. The major phenotypic consequences of these genetic manipulations were observed on the variation of the length of seedling roots. Seedlings lacking AtPrx33 transcripts have shorter roots than the wild-type controls and roots are still shorter in the double mutant. Seedlings overexpressing AtPrx34 exhibit significantly longer roots. These modifications of root length are accompanied by corresponding changes of cell length. The results suggest that AtPrx33 and Atprx34, two highly homologous Arabidopsis peroxidases, are involved in the reactions that promote cell elongation and that this occurs most likely within cell walls.
authors.affiliation: Laboratory of Plant Physiology, University of Geneva, Quai Ernest-Ansermet 30, 1211 Geneva 4, Switzerland.
authors.forename: Filippo
authors.initials: F
authors.lastname: Passardi
authors.forename: Michael
authors.initials: M
authors.lastname: Tognolli
authors.forename: Mireille
authors.initials: M
authors.lastname: De Meyer
authors.forename: Claude
authors.initials: C
authors.lastname: Penel
authors.forename: Christophe
authors.initials: C
authors.lastname: Dunand
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D049108:Cell Enlargement; D002473:Cell Wall / Q000201:enzymology* / Q000502:physiology; D015870:Gene Expression; D049452:Green Fluorescent Proteins; D016254:Mutagenesis, Insertional; D010544:Peroxidases / Q000502:physiology*; D018517:Plant Roots / Q000254:growth & development*; D034622:RNA Interference; D036226:Seedlings / Q000254:growth & development
chemical_list: D049452:Green Fluorescent Proteins; D010544:Peroxidases