JXB Advance Access originally published online on March 2, 2008
Journal of Experimental Botany 2008 59(4):875-889; doi:10.1093/jxb/ern013
© 2008 The Author(s).
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RESEARCH PAPER |
ZmXTH1, a new xyloglucan endotransglucosylase/hydrolase in maize, affects cell wall structure and composition in Arabidopsis thaliana*
1Laboratori de Genètica Molecular Vegetal, Consorci CSIC-IRTA, Jordi Girona 18-26, E-08034 Barcelona, Spain
2Institute of Molecular Plant Sciences, University of Edinburgh, Edinburgh EH9 3JH, UK
3Centre de Recherche sur les Macromolecules Vegetales (CERMAV, UPR-CNRS 5301), BP53, F-38041 Grenoble Cedex 09, France
4Departament d'Enginyeria Química, Universitat Autònoma de Barcelona, E-08193 Bellaterra, Spain
5Área de Fisiología Vegetal, Universidad de León, E-24071, Spain
To whom correspondence should be addressed. E-mail: rigau{at}ibmb.csic.es
Xyloglucan endotransglucosylase/hydrolases (XTHs; EC 2.4.1.207 and/or EC 3.2.1.15 [EC] 1) are enzymes involved in the modification of cell wall structure by cleaving and, often, also re-joining xyloglucan molecules in primary plant cell walls. Using a pool of antibodies raised against an enriched cell wall protein fraction, a new XTH cDNA in maize, ZmXTH1, has been isolated from a cDNA expression library obtained from the elongation zone of the maize root. The predicted protein has a putative N-terminal signal peptide and possesses the typical domains of this enzyme family, such as a catalytic domain that is homologous to that of Bacillus macerans β-glucanase, a putative N-glycosylation motif, and four cysteine residues in the central and C terminal regions of the ZmXTH1 protein. Phylogenetic analysis of ZmXTH1 reveals that it belongs to subgroup 4, so far only reported from Poaceae monocot species. ZmXTH1 has been expressed in Pichia pastoris (a methylotrophic yeast) and the recombinant enzyme showed xyloglucan endotransglucosylase but not xyloglucan endohydrolase activity, representing the first enzyme belonging to subgroup 4 characterized in maize so far. Expression data indicate that ZmXTH1 is expressed in elongating tissues, modulated by culture conditions, and induced by gibberellins. Transient expression assays in onion cells reveal that ZmXTH1 is directed to the cell wall, although weakly bound. Finally, Arabidopsis thaliana plants expressing ZmXTH1 show slightly increased xyloglucan endohydrolase activity and alterations in the cell wall structure and composition.
Key words: Cell elongation, cell wall, plant transformation, XEH, XET, XTH, Zea mays
* The sequence designated ZmXTH1 was submitted to the Nucleotide Sequence Database (accession number AJ875021).
Present address: Dipartimento di Biologia Evoluzionistica Sperimentale, Università di Bologna, 40126 Bologna, Italy.
Present address: Department of Biology, Faculty of Dentistry, Sinai University, PO Box 7, El Massaid-El Arish, North Sinai, Egypt.
Received 5 November 2007; Revised 7 January 2008 Accepted 7 January 2008