Cell wall carbohydrates in Phycomyces blakeslesanus Burgeff

Area of Science:

• * Mycology
• * Biochemistry
• * Cell Biology

Background:

• * Phycomyces blakesleeanus is a model organism for studying fungal development.
• * Cell wall composition is crucial for fungal structure, growth, and response to environmental stimuli.
• * Understanding carbohydrate dynamics in fungal cell walls provides insights into developmental processes.

Purpose of the Study:

• * To analyze the carbohydrate composition of cell walls in different developmental stages of Phycomyces blakesleeanus: spores, mycelium, and sporangiophores.
• * To investigate the incorporation of glucose into cell wall materials.
• * To examine the activity of the GDP-fucose synthesizing system during germination.

Main Methods:

• * Chemical analysis of cell wall polysaccharides.
• * Incorporation studies using uniformly labeled [U-14C]-glucose.
• * Enzyme activity assays for GDP-fucose synthesis.
• * Inhibition studies with cycloheximide and 5-fluorouracil.

Main Results:

• * Spore walls are primarily composed of glucose (>50%), uronic acids (~20%), mannose (~10%), and amino-sugars (~10%).
• * Hyphal cell walls show a shift, with amino-sugars becoming dominant (~45%), followed by uronic acids (~25%), glucose/fructose (~10%), and galactose (~6%).
• * Sporangiophores exhibit a high content of amino-sugars (~90%) and uronic acids (~6%). Traces of rhamnose were detected in all preparations.
• * [U-14C]-glucose incorporation confirmed these compositional patterns.
• * GDP-fucose synthesizing system activity increased during early germination and was sensitive to cycloheximide and 5-fluorouracil.

Conclusions:

• * The carbohydrate composition of Phycomyces blakesleeanus cell walls undergoes significant changes during development from spores to vegetative hyphae and reproductive sporangiophores.
• * Amino-sugars are a major component, particularly in actively growing and reproductive structures.
• * The observed changes suggest dynamic regulation of cell wall synthesis during fungal development.
• * The GDP-fucose synthesizing system appears to play a role in early germination, with its activity modulated by protein synthesis and RNA-related processes.