title: A novel transcriptional regulator, ClbR, controls the cellobiose- and cellulose-responsive induction of cellulase and xylanase genes regulated by two distinct signaling pathways in Aspergillus aculeatus.
abstract: The cellobiose- and cellulose-responsive induction of the FIII-avicelase (cbhI), FII-carboxymethyl cellulase (cmc2), and FIa-xylanase (xynIa) genes is not regulated by XlnR in Aspergillus aculeatus, which suggests that this fungus possesses an unknown cellulase gene-activating pathway. To identify the regulatory factors involved in this pathway, we constructed a random insertional mutagenesis library using Agrobacterium tumefaciens-mediated transformation of A. aculeatus NCP2, which harbors a transcriptional fusion between the cbhI promoter (P                 (                   CBHI                 )) and the orotidine 5'-phosphate decarboxylase gene (pyrG). Of the ~6,000 transformants screened, one 5-FOA-resistant transformant, S4-22, grew poorly on cellulose-containing media and exhibited reduced cellobiose-induced expression of cbhI. Southern blot analysis and nucleotide sequencing of the flanking regions of the T-DNA inserted in S4-22 indicated that the T-DNA was inserted within the coding region of a previously unreported Zn(II)(2)Cys(6)-transcription factor, which we designated the cellobiose response regulator (ClbR). The disruption of the clbR gene resulted in a significant reduction in the expression of cbhI and cmc2 in response to cellobiose and cellulose. Interestingly, the cellulose-responsive induction of FI-carboxymethyl cellulase (cmc1) and FIb-xylanase (xynIb) genes that are under the control of XlnR, was also reduced in the clbR-deficient mutant, but there was no effect on the induction of these genes in response to D-xylose or L-arabinose. These data demonstrate that ClbR participates in both XlnR-dependent and XlnR-independent cellobiose- and cellulose-responsive induction signaling pathways in A. aculeatus.
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai, Osaka 599-8531, Japan.
authors.forename: Emi
authors.initials: E
authors.lastname: Kunitake
authors.forename: Shuji
authors.initials: S
authors.lastname: Tani
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Sumitani
authors.forename: Takashi
authors.initials: T
authors.lastname: Kawaguchi
mesh_terms: D000595:Amino Acid Sequence; D001230:Aspergillus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D002475:Cellobiose / Q000378:metabolism; D002480:Cellulase / Q000096:biosynthesis*; D002482:Cellulose / Q000378:metabolism; D016000:Cluster Analysis; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000235:genetics; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic; D015966:Gene Expression Regulation, Fungal; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D014170:Transformation, Genetic; D014995:Xylosidases / Q000096:biosynthesis*
chemical_list: D003470:Culture Media; D004269:DNA, Bacterial; D004271:DNA, Fungal; C036483:T-DNA; D014157:Transcription Factors; D002475:Cellobiose; D002482:Cellulose; D014995:Xylosidases; D002480:Cellulase