The Arabidopsis IRX10 and IRX10-LIKE glycosyltransferases are critical for glucuronoxylan biosynthesis during secondary cell wall formation

Authors

  • Ai-Min Wu,

    1. Department of Forest Genetics and Plant Physiology, SLU, SE-901 83 Umeå, Sweden,
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  • Christophe Rihouey,

    1. Centre National de la Recherche Scientifique FRE 3090, Institut Fédératif de Recherche Multidisciplinaire sur les Peptides 23, Université de Rouen, 76821 Mont Saint Aignan Cedex, France,
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  • Martial Seveno,

    1. Centre National de la Recherche Scientifique FRE 3090, Institut Fédératif de Recherche Multidisciplinaire sur les Peptides 23, Université de Rouen, 76821 Mont Saint Aignan Cedex, France,
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  • Emma Hörnblad,

    1. Department of Forest Genetics and Plant Physiology, SLU, SE-901 83 Umeå, Sweden,
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  • Sunil Kumar Singh,

    1. Department of Forest Genetics and Plant Physiology, SLU, SE-901 83 Umeå, Sweden,
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  • Toshiro Matsunaga,

    1. National Agricultural Research Center, National Agriculture and Food Research Organisation, Tsukuba, Ibaraki, 305-8687, Japan,
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  • Tadashi Ishii,

    1. Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan, and
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  • Patrice Lerouge,

    1. Centre National de la Recherche Scientifique FRE 3090, Institut Fédératif de Recherche Multidisciplinaire sur les Peptides 23, Université de Rouen, 76821 Mont Saint Aignan Cedex, France,
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  • Alan Marchant

    Corresponding author
    1. Department of Forest Genetics and Plant Physiology, SLU, SE-901 83 Umeå, Sweden,
    2. School of Biological Sciences, University of Southampton, Boldrewood Campus, Southampton, SO16 7PX, UK
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  • Current address: CNRS UMR 5203, Plate-forme de protéomique Fonctionnelle, Institut de Génomique fonctionnelle, IFR3, 141 rue de la Cardonille, 34094 Montpellier cedex 05, France.

*(fax +44(0) 2380 594 459; e-mail A.Marchant@soton.ac.uk).

Summary

Arabidopsis IRX10 and IRX10-LIKE (IRX10-L) proteins are closely related members of the GT47 glycosyltransferase family. Single gene knock-outs of IRX10 or IRX10-L result in plants with either a weak or no mutant phenotype. However irx10 irx10-L double mutants are severely affected in their development, with a reduced rosette size and infrequent formation of a small infertile inflorescence. Plants homozygous for irx10 and heterozygous for irx10-L have an intermediate phenotype exhibiting a short inflorescence compared with the wild type, and an almost complete loss of fertility. Stem sections of the irx10 homozygous irx10-L heterozygous or irx10 irx10-L double mutants show decreased secondary cell-wall formation. NMR analysis shows that signals derived from the reducing end structure of glucuronoxylan were detected in the irx10 single mutant, and in the irx10 homozygous irx10-L heterozygous combination, but that the degree of polymerization of the xylan backbone was reduced compared with the wild type. Additionally, xylans from irx10 stem tissues have an almost complete loss of the GlcUA side chain, whereas the level of 4-O-Me-GlcUA was similar to that in wild type. Deletion of the predicted signal peptide from the N terminus of IRX10 or IRX10-L results in an inability to rescue the irx10 irx10-L double mutant phenotype. These findings demonstrate that IRX10 and IRX10-L perform a critical function in the synthesis of glucuronoxylan during secondary cell-wall formation, and that this activity is associated with the formation of the xylan backbone structure. This contrasts with the proposed function of the tobacco NpGUT1, which is closely related to the Arabidopsis IRX10 and IRX10-L proteins, in rhamnogalacturonan II biosynthesis.

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