Synthetic Gene Network with Positive Feedback Loop Amplifies Cellulase Gene Expression in Neurospora crassa

ACS Synth Biol. 2018 May 18;7(5):1395-1405. doi: 10.1021/acssynbio.8b00011. Epub 2018 Apr 20.


Second-generation or lignocellulosic biofuels are a tangible source of renewable energy, which is critical to combat climate change by reducing the carbon footprint. Filamentous fungi secrete cellulose-degrading enzymes called cellulases, which are used for production of lignocellulosic biofuels. However, inefficient production of cellulases is a major obstacle for industrial-scale production of second-generation biofuels. We used computational simulations to design and implement synthetic positive feedback loops to increase gene expression of a key transcription factor, CLR-2, that activates a large number of cellulases in a filamentous fungus, Neurospora crassa. Overexpression of CLR-2 reveals previously unappreciated roles of CLR-2 in lignocellulosic gene network, which enabled simultaneous induction of approximately 50% of 78 lignocellulosic degradation-related genes in our engineered Neurospora strains. This engineering results in dramatically increased cellulase activity due to cooperative orchestration of multiple enzymes involved in the cellulose degradation pathway. Our work provides a proof of principle in utilizing mathematical modeling and synthetic biology to improve the efficiency of cellulase synthesis for second-generation biofuel production.

Keywords: Neurospora crassa; cellulose; lignocellulose; positive feedback loop; second-generation biofuel.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cellulose / genetics*
  • Feedback, Physiological*
  • Fungal Proteins / genetics
  • Gene Expression Profiling
  • Gene Expression Regulation, Fungal
  • Gene Regulatory Networks
  • Genes, Synthetic*
  • Glycoside Hydrolases / genetics
  • Laccase / genetics
  • Lignin / genetics
  • Lignin / metabolism
  • Microorganisms, Genetically-Modified
  • Models, Biological
  • Neurospora crassa / genetics*
  • Transcription Factors / genetics


  • Fungal Proteins
  • Transcription Factors
  • lignocellulose
  • Cellulose
  • Lignin
  • Laccase
  • Glycoside Hydrolases
  • hemicellulase