Ultrastructure and composition of cell wall appositions in the roots of Asplenium (Polypodiales)

► Cell wall appositions appear at the contact site with micro-organisms in fern roots. ► Infecting microbes are immobilized when attempting to penetrate intracellularly. ► Cell wall appositions are made of a non-lignified polysaccharide matrix. ► Callose and lignins are absent, yellow-brown phenolic...

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Bibliographic Details
Published in:Micron (Oxford, England : 1993) England : 1993), 2011-12, Vol.42 (8), p.863-870
Main Authors: Leroux, O., Leroux, F., Bagniewska-Zadworna, A., Knox, J.P., Claeys, M., Bals, S., Viane, R.L.L.
Format: Article
Language:English
Subjects:
Apposition
Asplenium
callose
Cell Wall - chemistry
Cell Wall - ultrastructure
cell wall components
Cell walls
cellulose
Electron microscopy
Ferns
Ferns - chemistry
Ferns - microbiology
Ferns - ultrastructure
ferns and fern allies
Fluorescent Antibody Technique
fungi
Fungi - pathogenicity
Histology
Host-Pathogen Interactions
lignin
Microscopy
monoclonal antibodies
phenolic compounds
pigments
Plant Roots - chemistry
Plant Roots - microbiology
Plant Roots - ultrastructure
Plant–microbe-interaction
roots
Staining and Labeling - methods
transmission electron microscopy
ultrastructure
warts
xyloglucans
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Summary:► Cell wall appositions appear at the contact site with micro-organisms in fern roots. ► Infecting microbes are immobilized when attempting to penetrate intracellularly. ► Cell wall appositions are made of a non-lignified polysaccharide matrix. ► Callose and lignins are absent, yellow-brown phenolic compounds are present. ► They create a barrier protecting the root against infections. Cell wall appositions (CWAs), formed by the deposition of extra wall material at the contact site with microbial organisms, are an integral part of the response of plants to microbial challenge. Detailed histological studies of CWAs in fern roots do not exist. Using light and electron microscopy we examined the (ultra)structure of CWAs in the outer layers of roots of Asplenium species. All cell walls studded with CWAs were impregnated with yellow-brown pigments. CWAs had different shapes, ranging from warts to elongated branched structures, as observed with scanning and transmission electron microscopy. Ultrastructural study further showed that infecting fungi grow intramurally and that they are immobilized by CWAs when attempting to penetrate intracellularly. Immunolabelling experiments using monoclonal antibodies indicated pectic homogalacturonan, xyloglucan, mannan and cellulose in the CWAs, but tests for lignins and callose were negative. We conclude that these appositions are defense-related structures made of a non-lignified polysaccharide matrix on which phenolic compounds are deposited in order to create a barrier protecting the root against infections.
ISSN:0968-4328
1878-4291
DOI:10.1016/j.micron.2011.06.002