title: Intercellular pectic protuberances in Asplenium: new data on their composition and origin.
abstract: OBJECTIVE
  Projections of cell wall material into the intercellular spaces between parenchymatic cells have been observed since the mid-19th century. Histochemical staining suggested that these intercellular protuberances are probably pectic in nature, but uncertainties about their origin, composition and biological function(s) have remained.
  
  
  METHODS
  Using electron and light microscopy, including immunohistochemical methods, the structure and the presence of some major cell wall macromolecules in the intercellular pectic protuberances (IPPs) of the cortical parenchyma have been studied in a specimen of the Asplenium aethiopicum complex.
  
  
  RESULTS
  IPPs contained pectic homogalacturonan, but no evidence for pectic rhamnogalacturonan-I or xylogalacturonan epitopes was obtained. Arabinogalactan-proteins and xylan were not detected in cell walls, middle lamellae or IPPs of the cortical parenchyma, whereas xyloglucan was only found in its cell walls. Extensin (hydroxyproline-rich glycoproteins) LM1 and JIM11 and JIM20 epitopes were detected specifically in IPPs but not in their adjacent cell walls or middle lamellae.
  
  
  CONCLUSIONS
  It is postulated that IPPs do not originate exclusively from the middle lamellae because extensins were only found in IPPs and not in surrounding cell walls, intercellular space linings or middle lamellae, and because IPPs and their adjacent cell walls are discontinuous.
authors: Pteridology, Department of Biology, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium.
authors: Olivier
authors: O
authors: Leroux
authors: J Paul
authors: JP
authors: Knox
authors: Frederic
authors: F
authors: Leroux
authors: Alexander
authors: A
authors: Vrijdaghs
authors: Elke
authors: E
authors: Bellefroid
authors: Gaëtan
authors: G
authors: Borgonie
authors: Ronald L L
authors: RL
authors: Viane
mesh_terms: D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D029624:Ferns / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D007150:Immunohistochemistry; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D010368:Pectins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism
chemical_list: D010368:Pectins; D009195:Peroxidase