Intercellular pectic protuberances in Asplenium: new data on their composition and origin.
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.
Leroux
Olivier
O
Pteridology, Department of Biology, Ghent University, K.L. Ledeganckstraat 35, B-9000 Ghent, Belgium.
Knox
J Paul
JP
Leroux
Frederic
F
Vrijdaghs
Alexander
A
Bellefroid
Elke
E
Borgonie
Gaëtan
G
Viane
Ronald L L
RL
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
D010368:Pectins; D009195:Peroxidase