Phenolic acid residues e.g. feruloyl groups are found esterified to specific sugars of primary cell wall polysaccharides of plants and phenylpropanoid derivatives are incorporated into lignin. These phenolic moieties probably have profound effect on cell wall properties such as extensibility (and thus growth) and digestibility. The work described in this thesis is an investigation into some aspects of the biosynthesis of cell wall phenolic residues. The site and mechanism of the feruloylation of primary wall polysaccharides has been a matter of some debate, although it is likely to be enzyme mediated. Fescue and maize cell cultures were supplied with radiolabelled precursors in order to ascertain the kinetics of this process and thus its likely sub-cellular site. [<SUP>3</SUP>H]Arabinose uptake was negligible in maize cell cultures and labelling with [<SUP>14</SUP>C]glucose resulted in very high background levels of radioactivity making analysis of feruloylated fragments difficult. However, radiolabelled [<SUP>3</SUP>H]arabinose was rapidly taken up and incorporated into nascent polysaccharides of fescue cells and polymer bound [<SUP>3</SUP>H]arabinose residues were beginning to be feruloylated within 5 minutes of the radiolabelled precursor being supplied. However, radiolabelled polymers were not secreted into the culture medium until 15-30 minutes after this point. Assuming that the onset of secretion of radiolabelled polymers is the time before which essentially all of the radiolabel was internal to the plasma membrane, the data presented show that feruloylation of polymer bound [<SUP>3</SUP>H]arabinose residues must occur intraprotoplasmically. As feruloylation was shown to occur intraprotoplasmically and polysaccharide synthesis occurs mainly in the Golgi bodies, endomembrane preparations from maize cell cultures were assayed to ascertain the presence of feruloyl-CoA : polysaccharide feruloytransferase activity.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:659843 |
| Date | January 1993 |
| Creators | Myton, Kathryn E. |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/15473 |
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