Transcriptional level of representative cellulolytic functional genes in Trichoderma sp. by real-time RT-PCR during composting of yellow poplar chips. (A) Xylanases 1 and 2 (xyn 1 and xyn 2). (B) Cellobiohydrolase I (cbh 1), endoglucanase I (egl 1) and β-glucosidase 1 (bgl 1) were used in a set of representative species of Trichoderma genus. The gene expression level at each sampling time point of composting was first normalized with the Trichoderma sp. ITS rRNA, and then compared to their respective expression levels at 3 weeks (each of which was set as 1 fold). The primers for these genes were described in Table 3. Note that identical scales in the X axis of panels A-B allows a direct visual comparison of the magnitude of changes in gene expression levels.