Evidence of a critical role for cellodextrin transporte 2 (CDT-2) in both cellulose and hemicellulose degradation and utilization in Neurospora crassa

PLoS One. 2014 Feb 20;9(2):e89330. doi: 10.1371/journal.pone.0089330. eCollection 2014.

Abstract

CDT-1 and CDT-2 are two cellodextrin transporters discovered in the filamentous fungus Neurospora crassa. Previous studies focused on characterizing the role of these transporters in only a few conditions, including cellulose degradation, and the function of these two transporters is not yet completely understood. In this study, we show that deletion of cdt-2, but not cdt-1, results in growth defects not only on Avicel but also on xylan. cdt-2 can be highly induced by xylan, and this mutant has a xylodextrin consumption defect. Transcriptomic analysis of the cdt-2 deletion strain on Avicel and xylan showed that major cellulase and hemicellulase genes were significantly down-regulated in the cdt-2 deletion strain and artificial over expression of cdt-2 in N. crassa increased cellulase and hemicellulase production. Together, these data clearly show that CDT-2 plays a critical role in hemicellulose sensing and utilization. This is the first time a sugar transporter has been assigned a function in the hemicellulose degradation pathway. Furthermore, we found that the transcription factor XLR-1 is the major regulator of cdt-2, while cdt-1 is primarily regulated by CLR-1. These results deepen our understanding of the functions of both cellodextrin transporters, particularly for CDT-2. Our study also provides novel insight into the mechanisms for hemicellulose sensing and utilization in N. crassa, and may be applicable to other cellulolytic filamentous fungi.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biomarkers / metabolism
  • Cell Membrane / metabolism
  • Cellulase / genetics
  • Cellulase / metabolism
  • Cellulose / analogs & derivatives*
  • Cellulose / metabolism*
  • Dextrins / metabolism*
  • Gene Expression Profiling*
  • Glycoside Hydrolases / genetics
  • High-Throughput Nucleotide Sequencing
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism*
  • Neurospora crassa / genetics
  • Neurospora crassa / growth & development
  • Neurospora crassa / metabolism*
  • Oligonucleotide Array Sequence Analysis
  • Polysaccharides / metabolism*
  • RNA, Messenger / genetics
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction

Substances

  • Biomarkers
  • Dextrins
  • Membrane Transport Proteins
  • Polysaccharides
  • RNA, Messenger
  • hemicellulose
  • Cellulose
  • cellodextrin
  • Glycoside Hydrolases
  • hemicellulase
  • Cellulase

Grants and funding

This study was supported by 973 program of China (2013CB733600 and 2011CB707400), the Natural Science Foundation of China (Grant No. 31171207) and a sub-award from Energy Biosciences Institute (EBI) to CT. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.