Identification of cell-wall stress as a hexose-dependent and osmosensitive regulator of plant responses

Authors

  • Thorsten Hamann,

    Corresponding author
    1. Department of Biology, Carnegie Institution Department of Plant Biology, 260 Panama Street, Stanford, CA 94305, USA,
    2. Division of Biology, Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, South Kensington Campus, London SW7 2AZ, UK, and
    3. Porter Institute, Division of Biology, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
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  • Mark Bennett,

    1. Division of Biology, Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, South Kensington Campus, London SW7 2AZ, UK, and
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  • John Mansfield,

    1. Division of Biology, Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, South Kensington Campus, London SW7 2AZ, UK, and
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  • Christopher Somerville

    1. Department of Biology, Carnegie Institution Department of Plant Biology, 260 Panama Street, Stanford, CA 94305, USA,
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(fax +44 20 7594 5390; e-mail thamann@imperial.ac.uk).

Summary

Development, abiotic and biotic stress each affect the physical architecture and chemical composition of the plant cell wall, making maintenance of cell-wall integrity an important component of many plant processes. Cellulose biosynthesis inhibition (CBI) was employed to impair the functional integrity of the cell wall, and the plant’s response to this specific stress was characterized in an Arabidopsis seedling model system. CBI caused changes in the expression of genes involved in mechanoperception, the response to microbial challenge, and lignin and cell-wall polysaccharide biosynthesis. Following CBI, activation of a UDP-d-xylose 4-epimerase gene correlated with increases in arabinose and uronic acid content in seedling cell walls. Activation of pathogen response genes, lignin deposition and lesion formation were dependent on externally supplied sugars and were suppressed by osmotic support. Lignin deposition in the root elongation zone caused by CBI was reduced in atrbohd (NADPH oxidase) mutant seedlings but increased in jasmonic acid resistant1 (jar1-1) mutant seedlings. Phytohormone measurements showed that CBI-induced increases in jasmonic (JA) and salicylic acids were dependent on sugar availability and prevented by osmotic support. We show that CBI activates responses commonly attributed to both abiotic and microbial challenges. Glucose/sucrose and turgor pressure are critical components in maintenance of cell-wall integrity and the regulation of induced responses, including JA biosynthesis. Lignin deposition induced by CBI is regulated by JAR1-1 and NADPH oxidase-dependent signalling processes. Our results identify components of the mechanism that mediates the response to impairment of cell-wall integrity in Arabidopsis thaliana.

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