Cell-wall composition and polysaccharide synthase activity changes following photoinduction in Trichoderma viride

Area of Science:

• Mycology
• Biochemistry
• Cell Biology

Background:

• Trichoderma viride, a soil-borne fungus, exhibits light-regulated differentiation and metabolism.
• Cell wall composition is crucial for fungal structure and function.

Purpose of the Study:

• To investigate the impact of light on cell-wall synthesizing enzymes in Trichoderma viride.
• To analyze changes in cell wall composition following light exposure.

Main Methods:

• Illumination of dark-grown Trichoderma viride mycelia with white fluorescent light.
• Measurement of beta-1,3-glucan synthase and chitin synthase specific activities.
• Analysis of cell wall composition (beta-1,3-glucan and chitin content).
• Inhibition of protein synthesis using cycloheximide to assess de novo synthesis.

Main Results:

• A 10-minute light exposure increased beta-1,3-glucan synthase activity by ~130% and decreased chitin synthase activity by ~50%.
• These enzyme activity changes were dependent on de novo synthesis, as blocked protein synthesis prevented the effect.
• Beta-1,3-glucan content in cell walls increased by 35-50% in illuminated mycelia.
• Chitin content in cell walls remained largely unchanged after illumination.

Conclusions:

• Light is a significant regulator of cell wall biosynthesis in Trichoderma viride.
• Illumination induces the synthesis of beta-1,3-glucan synthase, leading to increased beta-1,3-glucan in cell walls.
• Chitin synthesis appears to be downregulated or less affected by light in this context.