<P><B>Abstract</B><P>We cloned a putative Talaromyces cellulolyticus (formerly known as Acremonium cellulolyticus) xlnR gene and isolated a xlnR disruptant strain. XlnR protein was localized in the nucleus. Xylanase production by the xlnR disruptant was lower than in the control strain at both the enzyme and transcriptional level. These data suggest that the XlnR protein regulates xylanase production in T. cellulolyticus.</P></P>