Characterization of cellulase secretion and Cre1-mediated carbon source repression in the potential lignocellulose-degrading strain Trichoderma asperellum T-1.
Trichoderma asperellum, a traditional bio-control species, was demonstrated to be an excellent candidate for lignocellulose degradation in this work. Comparing to the representatively industrial strain of Trichoderma reeseiQM6a, T. asperellum T-1 showed more robust growth, stronger spore production, faster secretion of lignocellulose-decomposing enzymes and better pH tolerance. The reducing sugar released by strain T-1 on the second day of fermentation was 87% higher than that of strain QM6a, although the maximum reducing sugar yield and the cellulase production persistence of the strain T-1 were lower. Our experiment found that the cellulase secretion was strongly inhibited by glucose, suggesting the existence of carbon source repression pathway in T. asperellum T-1. The inhibiting effect was enhanced with an increase in glucose concentration and was closely related to mycelium growth. SDS-PAGE and secondary mass-spectrum identification confirmed that the expression of endo-1,4-β-xylanase I in T. asperellum T-1 was down-regulated when glucose was added. The factor Cre1, which plays an important role in the down-regulation of the endo-1,4-β-xylanase I gene, was investigated by bioinformatics methods. The protein structure of Cre1, analyzed using multiple protein sequence alignment, indicates the existence of the Zn-fingers domain. Then, the binding sites of Cre1 on the endo-1,4-β-xylanase I gene promoter were further elucidated. This study is the first report about Cre1-mediated carbon repression in the bio-control strain T. asperellum T-1. All of the above results provided good references for better understanding T. asperellum T-1 and improving its application for lignocellulose degradation.
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, China.
Qun
Q
Wang
Institute of Environment Resource and Soil Fertilizer, Zhejiang Academy of Agriculture Science, Hangzhou, China.
Hui
H
Lin
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, China.
Qi
Q
Shen
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, China.
Xiaoping
X
Fan
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, China.
Naling
N
Bai
Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, China.
Yuhua
Y
Zhao
D000595:Amino Acid Sequence; D001665:Binding Sites; D002244:Carbon / Q000378:metabolism*; D002480:Cellulase / Q000378:metabolism*; D043364:Endo-1,4-beta Xylanases / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D008031:Lignin / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D017386:Sequence Homology, Amino Acid; D014242:Trichoderma / Q000378:metabolism*
D005656:Fungal Proteins; C036909:lignocellulose; D002244:Carbon; D008031:Lignin; D002480:Cellulase; D043364:Endo-1,4-beta Xylanases; D005947:Glucose