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Planta

, Volume 203, Issue 2, pp 174–181 | Cite as

Galactose loss and fruit ripening: high-molecular-weight arabinogalactans in the pectic polysaccharides of fruit cell walls

  • Robert J. Redgwell
  • Monica Fischer
  • Emma Kendal
  • Elspeth A. MacRae
Article

Abstract.

Cell wall material (CWM) was prepared from nine fruit species at two ripening stages (unripe and ripe) and extracted sequentially with 0.05 M trans-1,2-diaminocyclohexane-N,N,N′,N′-tetraacetic acid (CDTA), 0.05 M Na2CO3 and 4 M KOH. Each solubilised fraction and the CWM-residue remaining after 4 M KOH extraction was analysed for non-cellulosic sugar composition. A common pattern of distribution for polyuronide and pectin-associated neutral sugar was observed for all unripe fruit. Most polyuronide was extracted in the CDTA/Na2CO3 fractions while 70–93% of the neutral sugar was located on pectic polysaccharides in the 4 M KOH-soluble and CWM-residue fractions. During ripening, most of the galactose was lost from pectic polysaccharides in the CWM-residue. Partial solubilisation of these polysaccharides was achieved by treating the CWM-residue with endopolygalacturonase. The solubilised polysaccharides were separated into two fractions by ion-exchange chromatography. One of these contained polysaccharides with average molecular weights of 400 kDa or larger and consisted of between 70 and 90% arabinogalactan. The galactosyl residues were 80–90% β-1→4 linked, indicating largely unbranched side-chains. The arabinosyl residues were distributed among terminal, 3-, 5-, 2,5-, and 2,3,5-linked residues, indicating a highly ramified structure. The results are discussed with regard to the relationship between pectin solubilisation and galactose loss and their respective contribution to fruit softening.

Key words: Arabinogalactan Fruit (cell wall) Galactose Pectic polysaccharide Pectin solubilisation 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • Robert J. Redgwell
    • 1
  • Monica Fischer
    • 1
  • Emma Kendal
    • 1
  • Elspeth A. MacRae
    • 1
  1. 1.Horticulture and Food Research Institute of New Zealand Ltd., Mt Albert Research Centre, Private Bag 92 169, Auckland, New ZealandNZ

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