The filamentous fungus
Trichoderma reesei
is a model strain for cellulase production. Cellulase gene expression in
T. reesei
is controlled by multiple transcription factors. Here, we identified by comparative genomic screening a novel transcriptional activator ACE4 (
A
ctivator of
c
ellulase
e
xpression 4) that positively regulates cellulase gene expression on cellulose in
T. reesei
. Disruption of the
ace4
gene significantly decreased expression of four main cellulase genes, and the essential cellulase transcription factor encoding gene
ace3
. Overexpression of
ace4
increased cellulase production by approximately 22% compared to that in the parental strain. Further investigations using electrophoretic mobility shift assays, DNase I footprinting assays, and chromatin immunoprecipitation assays indicated that ACE4 directly binds to the promoter of cellulase genes by recognizing the two adjacent 5′-GGCC-3′ sequences. Additionally, ACE4 directly binds to the promoter of
ace3
and, in turn, regulates the expression of ACE3 to facilitate cellulase production. Collectively, these results demonstrate an important role for ACE4 in regulating cellulase gene expression, which will contribute to understanding the mechanism underlying cellulase expression in
T. reesei
.
IMPORTANCE
T. reesei
is commonly utilized in industry to produce cellulases, enzymes that degrade lignocellulosic biomass for the production of bioethanol and bio-based products.
T. reesei
is capable of rapidly initiating the biosynthesis of cellulases in the presence of cellulose, which has made it useful as a model fungus for studying gene expression in eukaryotes. Cellulase gene expression is controlled through multiple transcription factors at the transcriptional level. However, the molecular mechanisms by which transcription is controlled remain unclear. In the present study, we identified a novel transcription factor, ACE4, which regulates cellulase expression on cellulose by binding to the promoters of cellulase genes and the cellulase activator
ace3
. Our study not only expands the general functional understanding of the novel transcription factor ACE4 but also provides evidence for the regulatory mechanism mediating gene expression in
T. reesei
.
The VELVET A Orthologue VEL1 of Trichoderma reesei Regulates Fungal Development and Is Essential for Cellulase Gene Expression