Tuesday, April 20, 2010
11-16

Transcriptome, secretome and functional analysis of cre-1 in Neurospora crassa and its regulation during growth on crystalline cellulose

Jianping Sun and N. Louise Glass. Department of Plant and Microbial Biology, University of California, Berkeley, 111 Koshland Hall, Berkeley, CA 94720-3102

        In filamentous fungi, the production of the lignocellulolytic enzymes is controlled at the transcriptional level by the available carbon source. In many filamentous ascomycetes, such as Neurospora crassa, Trichoderma reesei and Aspergillus nidulans, glucose transcriptional repression is mediated by creA/cre-1, a zinc-finger protein related to Mig1p from Saccharomyces cerevisiae. The most well studied binding motif of CreA in A. nidulans was shown to be 5’-SYGGRG-3’ and context dependent; CRE-1 in T. reesei was shown to bind to the cbh-1 and cbh-2 promoter. In N. crassa, a Δcre-1 strain secreted more lignocellulolytic  enzymes and resulted in an increase in the expression of cellulase and hemicellulase genes on cellulose-based medium. Constitutive over-expression of cre-1 not only complements the phenotype of the Δcre-1 strain grown on crystalline cellulose but also results in much stronger suppression of both protein secretion and enzyme activity. These data indicate that CRE-1 acts as a repressor of the expression of cellulase and hemicellulase genes in N. crassa. To explore the role of CRE-1 in repression of lignocellulolytic genes, we determined the CRE-1 regulon by investigating the secretome and transcriptome of the Δcre-1 strain as compared to WT grown on crystalline cellulose. Strains containing deletions encoding 52 potential targets identified from microarray experiments were evaluated for phenotypic changes during growth on crystalline cellulose and for cellulase activity. Our data provide information on these potential CRE-1 targets under lignocellulolytic conditions and contribute to decipher the mechanism of the CRE-1 regulation of genes involved in plant cell wall deconstruction.

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