Articles
THE PHENOLS IN THE WAX AND IN THE SUBERIN POLYMER OF GREEN COTTON FIBRES AND THEIR FUNCTIONS
Article number
381_33
Pages
269 – 275
Language
Abstract
The secondary walls of green cotton fibres are characterised by up to 20 alternating layers of suberin and cellulose, as shown by electron microscopy and by modern chemical methods.
Cotton fibres do not lignify and are therefore a convenient material to study the phenolic constituents of suberin and associated waxes.
White cotton fibres may be taken as a control for phenols associated with the cuticle and the primary wall.
For labelling and inhibitor studies fibres produced by ovules cultured in vitro were used.
Esterified caffeic acid was the main phenol found in the wax of green cotton fibres.
After transesterification of exhaustively-extracted cell-wall residues caffeate was the main phenol liberated from the suberin polymer.
The fatty acid composition of cotton fibre suberin does not allow for extensive crosslinking, which according to the suberin model of Kolattukudy is mediated by a lignin-like aromatic matrix.
However, glycerol, a newly-described suberin monomer of green cotton fibres, is also a good crosslinking molecule.
When 2-aminoindan-2-phosphonic acid (AIP), an inhibitor of phenylalanine ammonia-lyase was added to ovules cultured in vitro, the fibres remained white and the amount of suberin was drastically reduced.
Fibres grown in the presence of AIP were also analysed in the electron microscope.
Secondary cell walls were well developed in the treated fibres, but the suberin was replaced by apparently empty spaces and the coherence between the cellulosic cell wall layers was lost.
It was concluded that cinnamic acids (probably mainly caffeoyl residues) are essential either for the attachment of suberin to cellulose or for the structure of the polymer itself.
The function of caffeate in the wax of green cotton fibres is not known.
It is assumed that its functions are related to the UV-absorbing and radical scavenging properties of the molecule.
Cotton fibres do not lignify and are therefore a convenient material to study the phenolic constituents of suberin and associated waxes.
White cotton fibres may be taken as a control for phenols associated with the cuticle and the primary wall.
For labelling and inhibitor studies fibres produced by ovules cultured in vitro were used.
Esterified caffeic acid was the main phenol found in the wax of green cotton fibres.
After transesterification of exhaustively-extracted cell-wall residues caffeate was the main phenol liberated from the suberin polymer.
The fatty acid composition of cotton fibre suberin does not allow for extensive crosslinking, which according to the suberin model of Kolattukudy is mediated by a lignin-like aromatic matrix.
However, glycerol, a newly-described suberin monomer of green cotton fibres, is also a good crosslinking molecule.
When 2-aminoindan-2-phosphonic acid (AIP), an inhibitor of phenylalanine ammonia-lyase was added to ovules cultured in vitro, the fibres remained white and the amount of suberin was drastically reduced.
Fibres grown in the presence of AIP were also analysed in the electron microscope.
Secondary cell walls were well developed in the treated fibres, but the suberin was replaced by apparently empty spaces and the coherence between the cellulosic cell wall layers was lost.
It was concluded that cinnamic acids (probably mainly caffeoyl residues) are essential either for the attachment of suberin to cellulose or for the structure of the polymer itself.
The function of caffeate in the wax of green cotton fibres is not known.
It is assumed that its functions are related to the UV-absorbing and radical scavenging properties of the molecule.
Authors
A. Schmutz, A. Buchala, U. Ryser, T. Jenny
Keywords
caffeic acid, cell wall, epidermis, glycerol, Gossypium, suberin, wax
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