Journal of Experimental Botany, Vol 49, 145-153, Copyright © 1998 by Oxford University Press
S Brosch-Salomon, M Hoftberger, A Holzinger and U Lutz-Meindl
In order to characterize the secretory pathway leading to multipolar tip
growth in green algae of the family Desmidiaceae, different general
polysaccharide stainings, such as the periodic acid-silver hexamine method
and the periodic acid-silver proteinate method as well as different lectins
specific to defined sugar residues have been employed. General
polysaccharide stainings label different kinds of secretory vesicles
starting from the onset of vesicle production up to their delivery into the
primary cell wall, however, the discrimination of Golgi products is
possible using lectins. Both gold-labelled lectins from Helix
pomatia and from Glycine max with affinity
to N-acetyl-D-galactosamine only produce labelling
of primary wall material containing 'dark vesicles' on the ultrathin
sections of high-pressure frozen and freeze-substituted
Micrasterias cells, whereas other vesicle types remain
unstained. 'Dark vesicles' are labelled when still attached to
trans-Golgi compartments, when distributed throughout
the cytoplasm or when fusing with the plasma membrane with the same
staining intensity which indicates that the sugars detected by the methods
used are present from the onset of visible vesicle production.
Gold-labelling of N-acetyl-D-galactosamine is also
observed in the primary cell wall. In control experiments the staining
vanishes when ultrathin sections are pre-incubated with
N-acetyl-D-galactosamine. Various other lectins with
affinity to different sugar residues than
N-acetyl-D-galactosamine do not produce staining of
the cell wall nor of any kind of secretory vesicles. As
N-acetyl-D-galactosamine is usually not present in
N-linked polysaccharides the results point towards the presence of
O-linked-glycoproteins in the primary cell wall of desmids.Key
words: Golgi, lectins, Micrasterias,
N-acetyl-D-galactosamine, secretion, vesicles.
ARTICLES
Ultrastructural localization of polysaccharides and N-actetyl-D-galactosamine in the secretory pathway of green algae (Desmidiaceae)
Institut fur Pflanzenphysiologie, Universitat Salzburg, A-5020 Salzburg, Austria; Corresponding author e-mail: Ursula.Meindl@sbg.ac.at
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