Intraprotoplasmic and wall-localised formation of arabinoxylan-bound diferulates and larger ferulate coupling-products in maize cell-suspension cultures.

摘要: Maize (Zea mays L.) cell cultures incorporated radioactivity from [14C]cinnamate into hydroxycinnamoyl-CoA derivatives and then polysaccharide-bound feruloyl residues. Within 5–20 min, the CoA pool had lost its 14C by turnover little or no further incorporation polysaccharides occurred. The system was thus effectively a pulse–chase experiment. Kinetics of radiolabelling diferulates (also known as dehydrodiferulates) varied with culture age. In young (1–3 d) cultures, [14C]feruloyl- [14C]diferuloyl residues were both detectable within 1 min feeding. Thus, dimerised 10 before secretion, data show that extensive coupling occurred intra-protoplasmically. Exogenous H2O2 (1 mM) caused additional coupling; therefore, wall-localised may have been peroxidase-limited. older (e.g. 4 less intraprotoplasmic occurred: during first 2.5 h, steady 1.4% total [14C]ferulate derivatives. contrast to situation in younger exogenous induced rapid 4- 6-fold increase all products, indicating walls H2O2-limited. 2- 4-d-old 14C-trimers larger products exceeded [14C]diferulates 3- 4-fold, but followed similar kinetics. although dimers ferulate can now be individually quantified, it appears trimers make major contribution cross-linking wall cultured maize cells. We argue arabinoxylans are cross-linked after secretion likely loosen tighten wall, respectively. consequences for control expansion response an oxidative burst discussed.