The transcription of a set of 32 putative xylanase genes from Fusarium graminearium was examined by quantitative PCR after growth on different carbon sources (hop cell wall, xylan, xylose, or carboxymethylcellulose). Growing on plant cell wall medium, this fungus displays a great diversity of expression of xylan-related genes, with 30 being induced. A second level of diversity exists because expression patterns can be very different for loci encoding enzymes with the same activity (the same EC number). The wealth of xylan-degrading enzymes and the differential expression confer on the fungus a great flexibility of reaction to variation in its environment. (c) 2006 Elsevier Inc. All rights reserved.