Transcriptome analysis profiling of MGD underlying cellulase induction by Trichoderma reesei

The mixture of glucose and disaccharide (MGD) as a soluble inducer prepared by transglycosylation of glucose can improve cellulase production level in Trichoderma reesei for biorefinery of lignocellulosic biomass compared with that on lactose, which is also a low-cost soluble inducer for lignocellulose enzyme generation. However, little is known about the gene expression profiles during MGD utilization in T. reesei. This study presents the molecular foundation on MGD to reveal the dramatic differences from that on lactose. MGD can provoke higher transcription of GH5-, GH6- and GH7-encoding cellulases up to 1.4-fold higher than that induced by lactose, but GH11- and GH74-encoding xylanases are downregulated by 1.7 and 4.4 times, respectively. Gene expression profiles suggest that transcription activators xyr1 and vib1 are significantly upregulated and the mitogen-activated protein kinase pathway is strengthened compared to the case of lactose induction. In addition, hac1-encoding UPR-specific transcription factors are significantly upregulated by MGD, which may enhance the correct folding of proteins. These findings provide a theoretical basis for further understanding the characterization of efficient cellulase production using MGD as an inducer in T. reesei, and offer potential strategies for strain improvement.