Biosynthesis of cell-wall ferulate and diferulates

Cell-wall hydroxycinnamates are derived from feruloyl-CoA, coumaroyl-CoA and other intermediates of the phenylpropanoid pathway. In normal (unelicited) tissues, hydroxycinnamates are ester-linked to pectins in some dicots and to arabinoxylans in grasses. The ester-linked hydroxycinnamates are thought to be formed by feruloylation of nascent polysaccharides in the Golgi apparatus, feruloyl-CoA perhaps being the substrate. It is not known whether dimerisation of polysaccharide-linked ferulate occurs in the Golgi apparatus as well as in the wall. In elicited dicot cells the immediate precursors of wall ferulate and coumarate include low molecular weight hydroxycinnamate derivatives (amides and esters) which are secreted into the cell wall and then oxidatively linked to polymers. The cell-wall hydroxycinnamates may, in some circumstances, be subject to turnover, though this may be a property of suspension cultured cells that is not necessarily shared with normal plant tissues.