Abstract:
Cell surfaces of susceptible host species (Mortierella pusllla and
Cboanepilora cucurbitarum ), resistant host (Pilascolomyces articulosus ),
nonhost (Mortierella candelabrum ) and the mycoparasite (Piptocepilalis
virginiana) were examined for sugar distribution patterns using light and
fluorescent microscopy techniques. The susceptible host, resistant host and
the mycoparasite species exhibited a similar sugar distribution profile; they
all showed N-acetyl glucosamine and D-glucose on their cell wall surfaces.
The nonhost cell wall surface showed a positive binding reaction to FITClectins
specific for N-acetyl glucosamine and also for OI.-fucose, N-acetyl
galactosamine and galactose. Treatment of these fungi with mild
concentrations of proteinases (both commercial as well as the mycoparasiteproteinase)
resulted in the revelation of additional sugars on the fungal cell
walls. The susceptible host treated with proteinase expressed higher levels
of N-acetyl glucosamine and D-glucose. The susceptible host also showed the
presence of OI.-fucose, N-acetyl galactosamine and galactose. The proteinasetreated
susceptible host cell walls also showed an increase in the levels of
attachment with the mycoparasite. Treatment of the resistant host with
proteinases revealed OI.-fucose in addition to N-acetyl glucosamine and
D-glucose. Treatment of the nonhost cell wall with proteinase resulted in the
exposure of low levels of D-glucose, in addition to sugars found on the
untreated nonhost cell wall surface. The mycoparasite treated with
proteinase revealed OI.-fucose, N-acetyl galactosamine and galactose on its cell
surface in addition to the sugars N-acetyl glucosamine and D-glucose.
Protoplasts were isolated from hosts and nonhost fungi and their
surfaces were examined for sugar distribution patterns. The susceptible host
and nonhost protoplast membranes showed all the sugars (N-acetyl
glucosamine, D-glucose, (It.-fucose, N-acetyl galactosamine and galactose)
tested for. The resistant host protoplast membrane however, had only
N-acetyl glucosamine and D-glucose exposed. This sugar distribution profile
resembles that exhibited by the untreated resistant host cell wall, as well as
that shown by the untreated mycoparasite cell surface. Only susceptible host
protoplasts were successful in attaching to the mycoparasite surface.
Resistant host protoplasts did not show any interaction with the
i
mycoparasite cell surface. Both susceptible as well as resistant host
protoplasts were incapable of attaching to agarose beads surface-coated with
specific carbohydrates. The mycoparasite however, did attach to agarose
beads surface-coated with either N-acetyl glucosamine, D-glucose/Dmannose
or o:,- methyl-D-mannose. The relevance of the cell wall and the
protoplast membrane in the light of the present results, in reacting
appropriately to bring about either a susceptible, a resistant or a nonhost
response has been discussed.
