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Plant Physiology Preview Published on April 7, 2006; 10.1104/pp.106.077701
Received January 24, 2006 The response of the leaf cell wall to desiccation in the resurrection plant Myrothamnus flabellifolius.
Department of Molecular and Cellular Biology, University of Cape Town, Private Bag, Rondebosch 7701, South Africa * Corresponding author; email: Lindsey{at}science.uct.ac.za.
The M. flabellifolius leaf cell wall and its response to desiccation were investigated using electron microscopic, biochemical and immunocytochemical techniques. Electron microscopy revealed desiccation-induced cell wall folding in the majority of mesophyll and epidermal cells. Thick walled vascular tissue and schlerenchymous ribs did not fold and supported the surrounding tissue, thereby limiting the extent of leaf shrinkage and allowing leaf morphology to be rapidly regained upon rehydration. Isolated cell walls from hydrated and desiccated M. flabellifolius leaves were fractionated into their constituent polymers and the resulting fractions analysed for monosaccharide content. Significant differences between hydrated and desiccated states were observed in the water soluble buffer extract, pectin fractions and the arabinogalactan protein rich extract. A marked increase in galacturonic acid was found in the alkali insoluble pectic fraction. Xyloglucan structure was analysed and shown to be of the standard dicotyledonous pattern. Immunocytochemical analysis determined the cellular location of the various epitopes associated with cell wall components, including pectin, xyloglucan and arabinogalactan proteins, in hydrated and desiccated leaf tissue. The most striking observation was a constitutively present high concentration of arabinose, which was associated with pectin, presumably in the form of arabinan polymers. We propose that the arabinan-rich leaf cell wall of M. flabellifolius possesses the necessary structural properties to be able to undergo repeated periods of desiccation and rehydration.
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