l -Sorbose induces cellulase gene transcription in the cellulolytic fungus Trichoderma reesei

Abstract

L-Sorbose has previously been assumed to stimulate cellulase formation in an indirect manner, different from that of sophorose in Trichoderma reesei. Through Northern blot analysis however, L-sorbose was found to regulate coordinately six cellulase genes (including eg13, whose behavior has not been studied so far) at transcriptional level, as is the case with sophorose in T. reesei strains PC-3-7 and QM9414. Dot blot analysis showed that the proportions of each cellulase mRNA to cbh1 mRNA, the largest amount of mRNA transcribed in T. reesei, did not change when L-sorbose or sophorose was used as an inducer in the PC-3-7 and QM9414 strains. cbh2 and egl1 mRNAs were about 45-60% and 20-30% of the cbh1 transcript, whereas small amounts of mRNA, 1-2% of cbh1, were observed on other endoglucanase genes. Furthermore, the PC-3-7 strain showed an enhanced level of cellulase gene transcription, about two- and four- to six-fold higher than that of the QM9414 strain with sophorose and L-sorbose, respectively.

Transcriptional Regulation of Biomass-degrading Enzymes in the Filamentous Fungus Trichoderma reesei

“…Previous studies (19,20,32) have shown that the known cellulase components and some hemicellulases are coordinately induced by certain substrates. The large magnitude in induction of genes encoding cellulase components and the toll on cellular resources used in synthesizing them suggests that the tendency toward tight coordinate regulation is likely to hold true for other genes whose products are involved in biomass degradation or in facilitating their synthesis.…”

“…Regulation of the Endoglucanases and the ␤-GlucosidasesThe previously identified endoglucanases are induced during growth on media containing cellulose, sophorose, or lactose (13,19,20). To determine whether the newly discovered endoglucanases are similarly regulated, we examined mRNA levels for each of these gene products by Northern blot.…”

“…Transcription of the major components of cellulase (CBHI/Cel7A, CBHII/Cel6A, EGI/Cel7B, EGII/Cel5A, EGIII/Cel12A, EGIV/Cel61A, and EGV/Cel45A) is induced not only by cellulose but also by a variety of disaccharides including lactose, cellobiose, and sophorose (glycosyl ␤-1,2-glucose) (13,19,20). Induction by these molecules is antagonized by the presence of the preferred carbon sources, glucose and fructose.…”

.ALPHA.-D-Glucans Having Unique Structures in Wheat Bran Extracts Stimulate the Production of Penicillolysin (a Metalloprotease) from Penicillium citrinum

“…16) In the case of cellulase production in Tricoderma, cellulose and its degraded oligosaccharides or sophorose are reported as inducers. 17,18) The above studies indicate that fungal extracellular polysaccharide hydrolytic enzymes use the substrates or those degraded products as inducers for the enzyme production. On the other hand, the protease used in this study did not require proteins or those degraded products as the inducer, but highly branched glucan as an inducer.…”

Global nutrient profiling by Phenotype MicroArrays: a tool complementing genomic and proteomic studies in conidial fungi

“…Since cellulase formation is triggered by sporulation (Kubicek, 1987), γ-aminobutyrate may constitute a link between cellulase induction and conidiation. On the other hand, the increased utilization of D-sorbitol by the improved producer strain QM 9414 may be linked to enhanced formation of L-sorbose, an inducer of cellulase formation in H. jecorina (Nogawa et al, 2001), because it is formed from D-sorbitol by the respective nicotinamide adenine dinucleotide phosphate (NADP)-dependent ketose reductase (Seiboth et al, 2007). While the importance of these two findings for cellulase production must be verified by reverse genetics, they have nevertheless pointed to two biochemical reactions, which may have a major impact on cellulase formation, and would have remained undetected without PM analysis.…”