Find in Library

<i>Trichoderma reesei</i> is a biotechnologically important filamentous fungus with the remarkable ability to secrete large amounts of enzymes, whose production is strongly affected by both the carbon and nitrogen sources. While the carbon metabolism regulators are extensively studied, the regulation of enzyme production by the nitrogen metabolism regulators is still poorly understood. In this study, the GATA transcription factor Are1, which is an orthologue of the <i>Aspergillus</i> global nitrogen regulator AREA, was identified and characterized for its functions in regulation of both protease and cellulase production in <i>T. reesei</i>. Deletion of the <i>are1</i> gene abolished the capability to secrete proteases, and complementation of the <i>are1</i> gene rescued the ability to produce proteases. Quantitative RT-PCR analysis revealed that the transcripts of protease genes <i>apw1</i> and <i>apw2</i> were also significantly reduced in the &#916;<i>are1</i> strain when grown in the medium with peptone as the nitrogen source. In addition, deletion of <i>are1</i> resulted in decreased cellulase production in the presence of (NH₄)₂SO₄. Consistent with the reduction of cellulase production, the transcription levels of the major cellulase genes, including <i>cbh1</i>, <i>cbh2</i>, <i>egl1</i>, and <i>egl2,</i> were dramatically decreased in &#916;<i>are1</i>. Sequence analysis showed that all promoter regions of the tested protease and cellulase genes contain the consensus GATA elements. However, the expression levels of the major cellulase transcription activator Xyr1 and the repressor Cre1 had no significant difference between &#916;<i>are1</i> and the parental strain QM9414, indicating that the regulatory mechanism deserves further investigation. Taken together, these results demonstrate the important role of Are1 in the regulation of protease and cellulase production in <i>T. reesei</i>, although these processes depend on the kind of nitrogen sources. The findings in this study contribute to the understanding of the regulation network of carbon and nitrogen sources in filamentous fungi.