Disclosed are: transcription regulatory factors capable of regulating the transcription or expression of genes for mannanases or cellulases, as mentioned below; and others. Specifically disclosed is a protein selected from the following proteins (a), (b) and (c): (a) a protein comprising the amino acid sequence depicted in SEQ ID NO:2; (b) a protein which comprises an amino acid sequence produced by deleting, substituting or adding one or several amino acid residues (e.g., 1 to 5 amino acid residues) in the amino acid sequence depicted in SEQ ID NO:2 and which is capable of regulating the transcription of genes for mannanases or cellulases; and (c) a protein which comprises an amino acid sequence having a 70% or higher sequence identity to the amino acid sequence depicted in SEQ ID NO:2 and which is capable of regulating the transcription of genes for mannanases or cellulases, or a partial fragment of the protein. Also specifically disclosed are a gene encoding the protein, and others.