Regulation of the lignocellulolytic response in filamentous fungi

• Zinc binuclear cluster transcription factors regulate the lignocellulosic response.
• General nutrient sensing pathways act upstream of the lignocellulolytic response.
• Unfolded protein response regulates lignocellulolytic enzyme production.

Lignocellulose is an abundant waste product of agricultural and processing industries that can be utilized as a renewable fuel substitute for petroleum-based fuels. Saprophytic filamentous fungi are an important source of plant cell wall degrading enzymes necessary to break down the complex carbohydrates found in plant cell walls into simple sugars. Zinc binuclear cluster transcription factors activate the transcription of plant cell wall degrading enzymes when fungal cells are exposed to plant biomass. Nutrient sensing pathways that prioritize the use of preferred carbon sources act upstream of these transcription factors to inhibit the energy intensive production of cell wall degrading enzymes when unnecessary, while downstream feedback from the fungal secretory system also acts to regulate the production of these enzymes. Understanding the regulation of the fungal lignocellulolytic response will be important as we strive to increase the efficiency of production of these enzymes.