Maize (Zea mays L.) cell cultures incorporated radioactivity from [14C]cinnamate into hydroxycinnamoyl-CoA derivatives and then into polysaccharide-bound feruloyl residues. Within 5-20 min, the CoA pool had lost its 14C by turnover and little or no further incorporation into polysaccharides then occurred. The system was thus effectively a pulse-chase experiment. Kinetics of radiolabelling of diferulates (also known as dehydrodiferulates) varied with culture age. In young (1-3 d) cultures, polysaccharide-bound [14C]feruloyl- and [14C]diferuloyl residues were both detectable within 1 min of [14C]cinnamate feeding. Thus, feruloyl residues were dimerised < 1 min after their attachment to polysaccharides. For at least the first 2.3 h after [14C]cinnamate feeding, polysaccharide-bound [14C]diferuloyl residues remained almost constant at approximately 7% of the total polysaccharide-bound [14C]ferulate derivatives. Since feruloyl residues are attached to polysaccharides < 1 min after the biosynthesis of the latter, and > 10 min before secretion, the data show that extensive feruloyl coupling occurred intra-protoplasmically. Exogenous H2O2 (1 mM) caused little additional feruloyl coupling; therefore, wall-localised coupling may have been peroxidase-limited. In older (e.g. 4 d) cultures, less intraprotoplasmic coupling occurred: during the first 2.5 h, polysaccharide-bound [14C]diferuloyl residues were a steady 1.4% of the total polysaccharide-bound [14C]ferulate derivatives. In contrast to the situation in younger cultures, exogenous H2O2 induced a rapid 4- to 6-fold increase in all coupling products, indicating that coupling in the walls was H2O2-limited. In both 2- and 4-d-old cultures, polysaccharide-bound 14C-trimers and larger coupling products exceeded [14C]diferulates 3- to 4-fold, but followed similar kinetics. Thus, although all known dimers of ferulate can now be individually quantified, it appears to be trimers and larger products that make the major contribution to cross-linking of wall polysaccharides in cultured maize cells. We argue that feruloyl arabinoxylans that are cross-linked before and after secretion are likely to loosen and tighten the cell wall, respectively. The consequences for the control of cell expansion and for the response of cell walls to an oxidative burst are discussed.
hose who might like to attend next year's meeting, 11 be held in Mainz, Germany from September 11th th. It will be a Congress (every third year) and is later than usual to avoid conflicting with the IMS meeting in Berkeley from August 21st to 27th and with IFLA in Brussels from September 5th to 10th. MariaCalderisi. NEW ACQUISITIONS NOUVELLES ACQUISITIONS Within the last few months, the Manuscript Collection of the Music Division of the National Library of Canada has added several interesting sets of papers to its holdings. During the summer of' 1976, the papers of Alfred E. Whitehead and Arnold Wa,ter were given to the Division by the families of these :anadian musicians. The m a t e r ~a l is extensive, covering most facets of their lives. Dr. Whitehead's papers include annotated copies of his organ repertoire, corrected copies of his philatelic writings, an almost complete set of his copyright contracts with a record of royalties received during his lifetime, a set
In recent years, successive waves of nationalism have swept across Canada and in their wake have left cultural centres, libraries, subsidies for the commissioning of artistic works, and a higher political awareness of the needs of culture and its place in the life and history of the country. Thus, more mvoney has been poured from the public coffers into various artistic endeavours, and the "middle-Canadiantt has been deluged with propaganda exhortin2 him to partake of the multiplicity of experiences offered to him during his ample leisure time.
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