Nozomu Shibata1,2, Hiroshi Kakeshita1, Kazuaki Igarashi3, Yasushi Takimura1, Yosuke Shida4, Wataru Ogasawara4, Tohru Koda2, Tomohisa Hasunuma5,6, Akihiko Kondo2,7,8. 1. Biological Science Research, Kao Corporation, 1334 Minato, Wakayama, Wakayama, 640-8580, Japan. 2. Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, Hyogo, 657-8501, Japan. 3. Biological Science Research, Kao Corporation, 2606 Akabane, Ichikai, Haga, Tochigi, 321-3497, Japan. 4. Department of Bioengineering, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata, 940-2188, Japan. 5. Graduate School of Science, Technology and Innovation, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, Hyogo, 657-8501, Japan. hasunuma@port.kobe-u.ac.jp. 6. Engineering Biology Research Center, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, Hyogo, 657-8501, Japan. hasunuma@port.kobe-u.ac.jp. 7. Engineering Biology Research Center, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, Hyogo, 657-8501, Japan. 8. Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada-ku, Kobe, 657-8501, Japan.
Abstract
BACKGROUND: Trichoderma reesei is a filamentous fungus that is important as an industrial producer of cellulases and hemicellulases due to its high secretion of these enzymes and outstanding performance in industrial fermenters. However, the reduction of enzyme production caused by carbon catabolite repression (CCR) has long been a problem. Disruption of a typical transcriptional regulator, Cre1, does not sufficiently suppress this reduction in the presence of glucose. RESULTS: We found that deletion of an α-tubulin (tubB) in T. reesei enhanced both the amount and rate of secretory protein production. Also, the tubulin-disrupted (ΔtubB) strain had high enzyme production and the same enzyme profile even if the strain was cultured in a glucose-containing medium. From transcriptome analysis, the ΔtubB strain exhibited upregulation of both cellulase and hemicellulase genes including some that were not originally induced by cellulose. Moreover, cellobiose transporter genes and the other sugar transporter genes were highly upregulated, and simultaneous uptake of glucose and cellobiose was also observed in the ΔtubB strain. These results suggested that the ΔtubB strain was released from CCR. CONCLUSION: Trichoderma reesei α-tubulin is involved in the transcription of cellulase and hemicellulase genes, as well as in CCR. This is the first report of overcoming CCR by disrupting α-tubulin gene in T. reesei. The disruption of α-tubulin is a promising approach for creating next-generation enzyme-producing strains of T. reesei.
BACKGROUND:Trichoderma reesei is a filamentous fungus that is important as an industrial producer of cellulases and hemicellulases due to its high secretion of these enzymes and outstanding performance in industrial fermenters. However, the reduction of enzyme production caused by carbon catabolite repression (CCR) has long been a problem. Disruption of a typical transcriptional regulator, Cre1, does not sufficiently suppress this reduction in the presence of glucose. RESULTS: We found that deletion of an α-tubulin (tubB) in T. reesei enhanced both the amount and rate of secretory protein production. Also, the tubulin-disrupted (ΔtubB) strain had high enzyme production and the same enzyme profile even if the strain was cultured in a glucose-containing medium. From transcriptome analysis, the ΔtubB strain exhibited upregulation of both cellulase and hemicellulase genes including some that were not originally induced by cellulose. Moreover, cellobiose transporter genes and the other sugar transporter genes were highly upregulated, and simultaneous uptake of glucose and cellobiose was also observed in the ΔtubB strain. These results suggested that the ΔtubB strain was released from CCR. CONCLUSION:Trichoderma reesei α-tubulin is involved in the transcription of cellulase and hemicellulase genes, as well as in CCR. This is the first report of overcoming CCR by disrupting α-tubulin gene in T. reesei. The disruption of α-tubulin is a promising approach for creating next-generation enzyme-producing strains of T. reesei.
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